Download What is a Solar System?

A Journey Through Space
Information taken from Wikipedia and Books by
Stephen and Lucy Hawking.
Compiled by Jainil Ajmera, Prakhar Mittal and Sanchit
Gupta
Contents
Unit 1. The Universe
1. The Universe : An Introduction
2. The Big Bang Theory
3. Galaxies
4. What is A Solar System?
5. Types Of Stars
6. Goldilocks Zone
7. Alpha Centauri
8. 55 Cancri
9. Constellations
10. Quasars
11. Redshifts
12. Pulsars
13. Nebula
Unit 2. Our Solar System
1. Our Solar System
2. Comets
3. Asteroids
4. Kuiper Belt
5. Meteors, Meteoroids and Meteorites
6. Sun
7. Planets and The Moon
8. Natural Satellites
9. Some facts on Earth
10. Mass Class
Unit 3. Space Exploration
1.
2.
3.
4.
5.
6.
Rockets
Spacesuits
Satellites
Robotic Space Travel
Manned Missions
NASA
7. Upcoming Missions
Unit 1 : The Universe
The Universe : An Introduction
The Big Bang Theory
You must have imagined how the universe was created? There are many stories
of which the one used by scientists is the Big bang theory. Back then, all the
matter that you see today was squeezed tightly into an area that was smaller
than the atom.
After what would be a tiny fraction of a second after the Big bang, everything
around looks much the same everywhere. But there is no fireball racing
outwards, instead you see a hot sea of material, filling all of the space. What
was this material? Scientists aren’t certain but whatever the material may be, it
was exotic that we can’t see today even with the best gadgets.
This tiny ocean of hot exotic material starts expanding as the space it fills
grows bigger and bigger at the speed of light. So, you see a lot of changes
happen in the first second after the Big Bang. The expansion of this tiny
universe led to the cooling of the hot sea of exotic material.
Now when the early universe is still much smaller than an atom, one of the
changes in the fluids leads to something known as inflation. The size of this tiny
universe doubles, then doubles again and goes on like this. This stretching made
the Universe smooth and almost same in all directions.
In this process, microscopic ripples are also stretched which will soon be the
cause of the birth of stars and galaxies.
Inflation ends and releases a large amount of energy and replaces the hot
exotic matter with quarks, protons, gluons, neutrons etc. The hot matter either
decayed into less exotic materials or it went to far parts of the Universe which
we may never see. The material which we see at this point of time is not as hot
as the exotic matter, but still hotter than anywhere today. Expansion continues,
and eventually the temperature falls enough for the quarks and antiquarks to
bind together to form neutrons and protons. There is little to be seen through
the plasma fog of the universe which has now become one second old.
Now over the few seconds, there are new photons made but still the visibility
level in the Universe is very poor.
As the Universe gets a few minutes old, the remaining photons and neutrons
form the first atomic nuclei, mainly of hydrogen and helium. After the frantic
action of the Universe in its first few minutes, it stays the same for the next
hundreds of thousands of years. Then, after 380,000 years, the fog finally
clears and electrons are captured by the nuclei to form the first whole atoms.
Now, only a fading red glow is to be seen which gets dimmer and dimmer. Soon,
it isn’t visible at all as we enter the Cosmic Dark Ages. The photons from that
glow are still moving which can now be detected through CMBs.
The Dark Ages stay for a few hundred millions of years. And a few quiet
changes are happening.
The microscopic ripples mean that some regions contained more mass than
average. This increases the pull of gravity towards those regions, bringing even
more mass in. Slowly, over millions of years, dense patches of gas and dark
matter gather as a result of the increased gravity. As the gas falls into these
patches, atoms speed up and become hotter. Every now and then, the gas
becomes hot enough to stop collapsing.
If the gas cloud collapses far enough, it breaks into spherical blobs so that the
heat can’t get out. Finally, a point is reached when hydrogen nuclei, in the cores
of the blobs become so hot and squashed together that they start to merge
into nuclei of helium and release nuclear energy. Now, the darkness is over as
the first of these blobs burst into bright light. The first stars are born and the
Dark Ages are over.
The first stars burn their hydrogen quickly, and in their final stages fuse
together whatever nuclei they find to make heavier atoms. These atoms are
scattered all around and get swept when new stars are born. This process
continues- new stars are born and die and create more ash to produce new
stars. Soon, the very familiar spiral-shaped galaxy is born- The Milky Way.
Nine billion years after the Big bang, the central star of the Solar System, our
Sun is born. After four and a half billion years, the only planet that is known to
support life, our Earth, is also born to whom still light of some parts of the
universe hasn’t reached.
Galaxies
What is a Galaxy?
A galaxy is a group of many stars, along with gas, dust, and dark matter. Gravity
holds galaxies together. Everything in a galaxy moves around a centre. The name
galaxy is taken from the Greek word Galaxia meaning milky, a reference to our
own galaxy, the Milky Way.
What are the types of Galaxies?
There are various types of galaxies: elliptical, spiral and lenticular galaxies,
which can all be with or without bars. All galaxies exist inside the universe.
There are probably over 170 billion (1.7x1011) galaxies within distance we can
see or the observable universe.
What are Elliptical Galaxies?
An elliptical galaxy is a galaxy having an approximately ellipsoidal shape and a
smooth, nearly featureless brightness profile. They are one of the three main
classes of galaxy originally described by Edwin Hubble in his 1936 work The
Realm of the Nebulae, along with spiral and lenticular galaxies. They range in
shape from nearly spherical to highly flat and in size from tens of millions to
over one trillion stars. Originally, Edwin Hubble thought that elliptical galaxies
may evolve into spiral galaxies, which later turned out to be false. Stars found
inside of elliptical galaxies are very much older than stars found in spiral
galaxies.
Sombrero Galaxy
What are Spiral Galaxies?
Spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and
a central concentration of stars known as the bulge. These are surrounded by a
much fainter halo of stars, many of which reside in globular clusters.
Spiral galaxies are named for the spiral structures that extend from the center
into the disk. The spiral arms are sites of ongoing star formation and are
brighter than the surrounding disk because of the young, hot OB stars that
inhabit them.
The Pinwheel Galaxy
What are Lenticular Galaxies?
A lenticular galaxy is a type of galaxy which is intermediate between an
elliptical galaxy and a spiral galaxy in galaxy morphological classification
schemes. Lenticular galaxies are disk galaxies (like spiral galaxies) which have
used up or lost most of their interstellar matter and therefore have very little
ongoing star formation.
Spindle Galaxy
Is Milky Way a Barred Spiral Galaxy?
Yes, Milky Way is a Barred Spiral Galaxy.
Which is the nearest galaxy to us?
The closest dwarf galaxy to the Milky Way is Canis Major Dwarf Galaxy while
the closest Equivalent galaxy is Andromeda.
Galaxy
Group
Notes
Membership
1
Milky Way
Local Group Home galaxy of Earth
2
Canis Major Dwarf
Local Group
Satellite of Milky Way
(accretion by Milky Way)
3
Sagittarius Dwarf
Sphr SagDEG
Local Group
Satellite of Milky Way (partial
accretion by Milky Way)
4
Ursa Major II Dwarf
Local Group
Satellite of Milky Way
(accretion by Milky Way)
#
Large Magellanic Cloud
Local Group Satellite of Milky Way
(LMC)
5
Boötes Dwarf
6
Small Magellanic Cloud
Local Group Satellite of Milky Way
(SMC, NGC 292)
–
Ursa Minor Dwarf
Local Group Satellite of Milky Way
8
Draco Dwarf (DDO
208)
Local Group
*
NGC 2419
9
Sextans Dwarf Sph
Local Group Satellite of Milky Way
Satellite of Milky Way with a
large amount of dark matter
Brightest remote MW globular
cluster
Local Group Satellite of Milky Way
10
Sculptor Dwarf (E351Local Group Satellite of Milky Way
G30)
11
Ursa Major I Dwarf
Local Group Satellite of Milky Way
(UMa I dSph)
—
Carina Dwarf (E206G220)
Local Group Satellite of Milky Way
13
Fornax Dwarf (E356G04)
Local Group Satellite of Milky Way
14
Leo II Dwarf (Leo B,
DDO 93)
Local Group Satellite of Milky Way
15
Leo I Dwarf (DDO 74) Local Group Satellite of Milky Way
16
Leo T Dwarf
Local Group Satellite of Milky Way
17
Phoenix Dwarf Galaxy
(P 6830)
Local Group Satellite of Milky Way
18
Barnard's Galaxy (NGC
Local Group Satellite of Milky Way
6822)
*
MGC1
Local Group
19
NGC 185
Local Group Satellite of Andromeda
20
Andromeda II
Local Group Satellite of Andromeda
Isolated cluster at ~200 kpc
from M31
Well I just saw Local Group and Satellite of Milky Way in the above table.
What do they mean?
The local group is a group of 100 – 200 galaxies which are very close to each
other. And the Satellite of Milky Way means that a galaxy that is merging
slowly into our galaxy and after some time it will be a part of the Milky Way.
Is Andromeda bigger than our Milky Way?
The Milky Way is twice the weight of Andromeda but still Andromeda has a
larger number of stars than the Milky Way.
Is it true that millions of years later, Andromeda and Milky Way galaxy
will merge into each other?
The Andromeda–Milky Way collision is a predicted galaxy collision that will take
place in approximately 4 billion years' time between the two largest galaxies in
the Local Group—the Andromeda Galaxy and the Milky Way, which contains the
Solar System and Earth.
While the Andromeda Galaxy contains about one trillion (1012) stars and the
Milky Way contains about three hundred billion (3x1011); the chance of even
two stars colliding is negligible because of the huge distances between each pair
of stars. For example, the nearest star to the Sun is Proxima Centauri, about
3x107 solar diameters (4x1013 km or 4.27 ly) away. If the Sun were a ping-pong
ball in Paris, the equivalent Proxima Centauri would be a pea-sized ball in Berlin
(and the Milky Way would be about 1.9x107 km wide, about a third of the
distance to Mars).
Stars are much denser near the centres of each galaxy with an average
separation of only 1.6x1011 km. But that is still a density which represents one
ping-pong ball every 3.2 km. Thus, it is extremely unlikely that any two stars
may collide.
What is Canis Mojor Dwarf Galaxy?
The Canis Major Dwarf Galaxy is a supposed small irregular galaxy in the Local
Group, located in the same part of the sky as the constellation Canis Major.
The galaxy contains a relatively high percentage of red giant stars, and is
thought to contain an estimated one billion stars in all.
The Canis Major Dwarf Galaxy is classified as an irregular galaxy and is now
thought to be the closest neighbouring galaxy to our location in the Milky Way,
being located about 25,000 light-years away from our Solar System and 42,000
light-years from the Galactic Center. It has a roughly elliptical shape and is
thought to contain as many stars as the Sagittarius Dwarf Elliptical Galaxy, the
previous contender for closest galaxy to our location in the Milky Way.
Astronomers believe that the Canis Major Dwarf Galaxy is in the process of
being pulled apart by the gravitational field of the more massive Milky Way
galaxy. The main body of the galaxy is extremely degraded.
Which is the largest known galaxy?
IC 1101 is a supergiant elliptical galaxy at the center of the Abell 2029 galaxy
cluster. It is 1.07 billion light years away in the constellation of Serpens. It was
discovered in June 19, 1790 by William Herschel.
The galaxy has a diameter of approximately 6 million light years i.e.
5,676,317,041,000,000,000,000 kilometers, which makes it currently (as of
2012) the largest known galaxy in terms of breadth. It is the central galaxy of a
massive cluster containing a mass (mostly dark matter) of roughly 100 trillion
stars. Being more than 50 times the size of the Milky Way and 2000 times as
massive, if it were in place of our galaxy, it would swallow up the Large
Magellanic Cloud, Small Magellanic Cloud, Andromeda Galaxy, and Triangulum
Galaxy. IC 1101 owes its size to many collisions of much smaller galaxies about
the size of the Milky Way and Andromeda galaxies.
IC 1101
What is a Solar System?
Types Of Stars
A star is a star, right? Well, not exactly. There are many different types of
stars, from the tiny brown dwarfs to the red and blue supergiants. There are
even more bizarre kinds of stars, like neutron stars and Wolf-Rayet stars. Let’s
take a look at all the different types of stars there are.
1. Main Sequence Stars
A star is said to be born once nuclear fusion commences in its
core. At this point it is, regardless of mass, considered a main
sequence star. This is where the majority of a star's life is
lived. Our Sun has been on the main sequence for about 5
billion years, and will persist for another 5 billion years or so
before it transitions to become a Red Giant Star.
2. Red Giant Stars
Once a star has used up all of its hydrogen fuel in its core it
transitions off the main sequence and becomes a red giant.
Depending on the mass of the star it can oscillate between
various states before ultimately becoming either a white
dwarf, neutron star or black hole. One of our nearest
neighbors (galactically speaking), Betlegeuse is currently in its red giant phase
and is expected to go supernova at any time.
3. White Dwarfs
When low-mass stars, like our Sun, reach the end of their
lives they enter the red giant phase. But the outward
radiation pressure overwhelms the gravitational pressure
and the star expands farther and farther out into space.
Eventually, the outer envelope of the star begins to merge with interstellar
space and all that is left behind is the remnant of the star's core. This core is a
smoldering ball of carbon and other various elements that glows as it cools.
While often referred to as a star, a white dwarf is not technically a star as it
does not undergo nuclear fusion. Rather it is a stellar REMNANT, like a black
hole or neutron star. Eventually it is this type of object that will be the sole
remains of our Sun billions of years from now.
4. Neutron Stars
A neutron star, like a white dwarf or black hole, is actually not
a star but a stellar remnant. When a massive star reaches the
end of its life it undergoes a supernova explosion, leaving
behind its incredibly dense core. A soup-can full of neutron
star material would have about the same mass as our Moon.
There only objects known to exist in the Universe that have greater density are
black holes.
6. Brown Dwarfs
Brown Dwarfs are not actually stars, but rather "failed" stars.
They form in the same manner as normal stars, however they
never quite accumulate enough mass to ignite nuclear fusion in
their cores. Therefore they are noticeably smaller than main
sequence stars. In fact those that have been detected are
more similar to the planet Jupiter in size, though much more massive (and hence
much denser).
7. Variable Stars
Most stars we see in the night sky maintain a constant
brightness (the twinkling we sometimes see is actually an
atmospheric effect and not a variation of the star), but
some stars actually do vary. While some stars owe their
variation to their rotation (like rotating neutron stars,
called pulsars) most variable stars change brightness because of their continual
expansion and contraction. The period of pulsation observed is directly
proportional to its intrinsic brightness. For this reason, variable stars are used
to measure distances since their period and apparent brightness (how bright
they appear to us on Earth) can be sued to calculate how far away they are from
us.
Well there are three more types of stars but we will not discuss them in detail Protostar
A protostar is what you have before a star forms. A protostar is a collection of
gas that has collapsed down from a giant molecular cloud. The protostar phase
of stellar evolution lasts about 100,000 years. Over time, gravity and pressure
increase, forcing the protostar to collapse down. All of the energy release by
the protostar comes only from the heating caused by the gravitational energy –
nuclear fusion reactions haven’t started yet.
T Tauri Star
A T Tauri star is stage in a star’s formation and evolution right before it
becomes a main sequence star. This phase occurs at the end of the protostar
phase, when the gravitational pressure holding the star together is the source
of all its energy. T Tauri stars don’t have enough pressure and temperature at
their cores to generate nuclear fusion, but they do resemble main sequence
stars; they’re about the same temperature but brighter because they’re a
larger. T Tauri stars can have large areas of sunspot coverage, and have intense
X-ray flares and extremely powerful stellar winds. Stars will remain in the T
Tauri stage for about 100 million years.
Supergiant Stars
The largest stars in the Universe are supergiant stars. These are monsters with
dozens of times the mass of the Sun. Unlike a relatively stable star like the
Sun, supergiants are consuming hydrogen fuel at an enormous rate and will
consume all the fuel in their cores within just a few million years. Supergiant
stars live fast and die young, detonating as supernovae; completely
disintegrating themselves in the process.
Goldilock’s Zone
Our Milky Way contains at least 100 billion rocky planets. Our Sun has four :
namely Mercury, Venus, Earth and Mars – but only Earth has life.
What makes Earth special?
The answer is water, especially in liquid form. Water is the great mixer for
chemicals, breaking the apart, spreading them out and bringing the back
together as new biological building blocks, such as proteins and DNA. Without
water, life seems unlikely.
To support life, a planet’s temperature must be between zero and 100 degrees
Celsius to keep water in liquid form.
A planet orbiting too close to its home star will receive so much light energy
that it will heat up to scorching temperatures, boiling all the water into steam.
Planets too far from their star will receive very little light energy, keeping the
planet, keeping the planet so cold that any water will remain ice. Indeed, Mars
has its water trapped as ice at the north and south poles.
There is a certain distance from every star where a planet receives as much
light as it emits heat. That energy balance serves as a thermostat, keeping the
temperature lukewarm – just right to keep the water liquid in lakes and oceans.
In this ‘Goldilocks Zone’ around a star, any planet would stay war and bathed in
water for millions of years, allowing the chemistry to flourish.
Alpha Centauri
At just four light years away, Alpha Centauri is the closest star system to our
Sun. In the night sky looks like just one star, but is in fact a triplet. Two Sun –
like stars, Alpha Centauri A and Alpha Centauri B – separated but around 23
times the distance between the Earth and the Sun – orbit a common centre
about once every 80 years. There is a third, fainter star in the system, Proxima
Centauri, which orbits the other two but at a huge distance from them. Proxima
is the nearest of the three of us.
Alpha A is a yellow star and very similar to our Sun but brighter and slightly
more massive. Alpha B is an orange star, slightly cooler than our Sun and a bit
less massive. It is thought that the Alpha Centauri system formed around 1000
million years before our Solar System. Both Alpha A and Alpha B are stable
stars, like our Sun, and like our Sun may have been born surrounded by dusty
planet – forming discs.
Alpha A and Alpha B are binary stars. This means that if you were standing on a
planet orbiting one of the planets orbiting one of them, at certain times you can
see two suns in the sky.
In 2008 scientists suggested that planets ay have been formed around one or
both of the stars. From a telescope in Chile they are now monitoring Alpha
Centauri very carefully to see whether small wobbles in starlight will show us
planets in orbit in our nearest star system. Astronomers are looking at Alpha
Centauri B to see whether this bright, calm star will reveal Earth – like worlds
around it.
Alpha Centauri can be seen from Earth’s Southern Hemisphere, where it is one
of the stars of the Centaurus constellation. Its proper name – Rigel Kentaurus –
means ‘centaur’s foot’. Alpha Centauri is its Bayer designation (a system of star
– naming introduced by astronomer Johann Bayer in 1603).
55 Cancri
55 Cancri is a star system 41 light years away from us in the direction of the
Cancri constellation. It is a binary system : 55 Cancri A is a yellow star and 55
Cancri B is a smaller, red dwarf star. These two stars orbit each other at 1000
times the distance between the Earth and the Sun!
On 6 November 2007 astronomers discovered a record – breaking fifth planet
in orbit around Cancri B. This makes it the only star system other than our Sun
known to have as many as five planet!
The first planet around Cancri A was discovered in 1996. Named Cancri b, it is
the size of Jupiter and orbits close to the star. In 2002 two more planets
(Cancri c and d) were discovered; in 2004 a fourth planet, Cancri e, which is the
size of Neptune and takes just three days to orbit Cancri A. This planet would
be scorchingly hot, with surface temperature up to 1500 degrees Celsius!
The fifth planet, Cancri f, is around half the mass of Saturn and lies in the
habitable zone (Goldilocks Zone) zone of its star. This planet is a giant ball of
gas – mostly made of Helium and Hydrogen, like Saturn in our solar system. But
there may be moons in orbit around Cancri f or rocky planets within Cancri’s
Goldilocks Zone where liquid water could exist on the surface!
Cancri f orbits its star at a distance of 0.781 Astronomical Unit. An AU is the
measure of the distance that astronomers use to talk about orbits and distance
from stars. One Au = 93 million million miles, which is the average distance from
the Earth to the Sun. Given that there is life on Earth and liquid water on the
surface of our planet, we can say that one AU or 93 million million miles from
our Sun is within the habitable zone of our Solar System. So for stars of
roughly the mass, age and luminosity of our Sun, we can guess that a planet
orbiting its star at around one AU might be in the Goldilocks Zone. Cancri A is
an older and dimer star than our Sun, and astronomers calculate that its
habitable zone lies between 0.5 AU and 2 AUs away from it, which puts Cancri f
in a good position!
It is very difficult to spot multiple planets around a star because each planet
produces its own stellar wobble. To find more than one planet, astronomers need
to be able to spot wobbles within wobbles! Astronomers in California have been
monitoring 55 Cancri for over 20 years to make these discoveries!
Constellations
Quasars
A quasar (or Quasi-Stellar Radio Source) occurs when gas near a supermassive
black hole at the centre of a distant galaxy goes into the black hole (at very
high speed), but electromagnetic forces cause it to swirl around above the hole
and blast off into space in the form of huge jets of energy. When the gas gets
close to the black hole, the gas heats up because of friction. Therefore, the gas
glows very brightly, and this light is visible on the other side of the Universe. It
is often brighter than the whole galaxy that quasar is in. The first quasars were
discovered with radio telescopes in the late 1950s and are still actively studied
by astronomers today.
Astronomers now think that when a galaxy has a quasar, the quasar changes the
galaxy. Gas and dust from the galaxy falls onto the quasar, and the bright
quasar heats up gas in the galaxy. This stops new stars from forming in the
galaxy, so many of the elliptical galaxies we see in the universe now may have
once had a quasar in their centers. When the gas and dust stop falling onto the
quasar and firîng out, it stops being so bright and the black hole becomes very
hard to see.
Redshifts
Red shift is a way astronomers use to tell the distance of any object that is
very far away in the Universe. The red shift is one example of the Doppler
effect.
The easiest way to experience the Doppler effect is to listen to a moving train.
As the train moves towards a person, the sound it makes as it comes towards
them sounds like it has a higher tone, since the frequency of the sound is
squeezed together a little bit. As the train speeds away, the sound gets
stretched out, and sounds lower in tone. The same happens with light when an
object that emits light moves very fast. An object, like a star or a galaxy that is
far away and moving toward us, will look more blue than it normally does. This is
called blue shift. A star or galaxy moving away from us will look more red than it
should, which is where red shift got its name, since the colors are shifted red.
The reason astronomers can tell how far the light gets shifted is because
certain chemical elements, like the calcium in bones or the oxygen people
breathe has a unique fingerprint of light that no other chemical element has.
They can see what colors of light are coming from a star, and see what it is
made of. Once they know that, they check to see the difference between where
the fingerprint, called spectral lines, are actually at, and then look at where
they are supposed to be. When they see that, they can tell how far away the
star is, whether it is moving toward us or away from us, and also how fast it is
going, since the faster it goes, the farther the distance the spectral lines are
from where they should be.
Red shift is important because astronomers used it to figure out that the
Universe is expanding.
Pulsars
Pulsars are neutron stars that turn quickly and produce electromagnetic
radiation that can be received in the form of radio waves. The strength of
radiation changes according to a regular period of time, which is thought to
match to the period of time in which the star turns. Pulsars also show a socalled lighthouse effect, which occurs when the light and other radiation from a
pulsar are only seen at certain periods of time and not all of the time. Werner
Becker of the Max-Planck-Institut für extraterrestrische Physik recently said,
"The theory of how pulsars emit their radiation is still in its infancy, even after
nearly forty years of work.. There are many models but no accepted theory." In
other words, scientists are still just beginning to understand pulsars and they
do not all agree on how pulsars work.
The first pulsar was discovered in 1967, by Jocelyn Bell Burnell and Antony
Hewish of the University of Cambridge, UK. At first, they did not understand
why pulsars have a regular change in the strength of radiation, they called their
discovery LGM-1, for ":little green men"; their pulsar was later called CP 1919,
and is now known by a number of names including PSR 1919+21. The word pulsar
is short for "pulsating star", and was first seen written in 1968.
A Pulsar
Nebula
A nebula, which comes from the Latin word for mist or cloud, is an interstellar
cloud of dust, hydrogen, helium, and other gases.
An interstellar cloud is dust, plasma, or ionized gas in a galaxy. The Persian
astronomer, Abd al-Rahman al-Sufi, mentioned a true nebula for the first time
in his book, Book of Fixed Stars (964). He said that there was a "little cloud"
near the Andromeda Galaxy
A nebula is usually made up of hydrogen gas and plasma. It may be the first
stage of a star's cycle, but it may also be one of the last stages.
Many nebulae or stars form from the gravitational collapse of gas in the
interstellar medium or ISM. As the material collapses contracts, massive stars
may form in the center, and their ultraviolet radiation ionises the surrounding
gas, making it visible at optical wavelengths.
Examples of these types of nebulae are the Rosette Nebula and the Pelican
Nebula. The size of these nebulae, known as HII regions, varies depending on
the size of the original cloud of gas. These are sites where star formation
occurs. The formed stars are sometimes known as a young, loose cluster.
Some nebulae are formed as the result of supernova explosions, the death
throes of massive, short-lived stars. The materials thrown off from the
supernova explosion are ionized by the energy and the compact object that it
can produce. One of the best examples of this is the Crab Nebula, in Taurus.
The supernova event was recorded in the year 1054 and is labelled SN 1054.
The compact object that was created after the explosion lies in the center of
the Crab Nebula and is a neutron star.
Other nebulae may form as planetary nebulae. This is the final stage of a lowmass star's life, like Earth's Sun. Stars with a mass up to 8-10 solar masses
evolve into red giants and slowly lose their outer layers during pulsations in
their atmospheres. When a star has lost enough material, its temperature
increases and the ultraviolet radiation it emits can ionize the surrounding nebula
that it has thrown off. The nebula is 97% Hydrogen and 3% Helium with trace
materials.
In the past galaxies and star clusters were also called 'nebulae'.
Types of nebulae
Nebulae can be sorted by why we can see them.
Emission nebulae
Emission nebulae make their own light. Usually the gases in an emission nebula
are ionized. This makes them glow. Emission nebulae are usually red because
they usually produce red light.
Reflection nebulae
Reflection nebulae reflect light from nearby stars.
Dark nebulae
Dark nebulae do not emit light or reflect light. They block the light from stars
that are far away.
Unit 2 : Our Solar System
Our Solar System
Comets
Asteroids
Asteroids are small Solar System bodies or dwarf planets that are not comets.
The term asteroids historically referred to objects inside the orbit of Jupiter.
They have also been called planetoids, especially the larger ones. These terms
have historically been applied to any astronomical object orbiting the Sun that
did not show the disk of a planet and was not observed to have the
characteristics of an active comet, but as small objects in the outer Solar
System were discovered, their volatile-based surfaces were found to more
closely resemble comets, and so were often distinguished from traditional
asteroids. Thus the term asteroid has come increasingly to refer specifically to
the small bodies of the inner Solar System within the orbit of Jupiter, which
are usually rocky or metallic. They are grouped with the outer bodies—
centaurs, Neptune trojans, and trans-Neptunian objects—as minor planets,
which is the term preferred in astronomical circles. In this article the term
"asteroid" refers to the minor planets of the inner Solar System.
There are millions of asteroids, many thought to be the shattered remnants
of planetesimals, bodies within the young Sun's solar nebula that never grew
large enough to become planets. The large majority of known asteroids orbit in
the asteroid belt between the orbits of Mars and Jupiter or co-orbital with
Jupiter (the Jupiter Trojans). However, other orbital families exist with
significant populations, including the near-Earth asteroids. Individual asteroids
are classified by their characteristic spectra, with the majority falling into
three main groups: C-type, S-type, and M-type. These were named after and are
generally
identified
with carbon-rich,stony,
and metallic compositions,
respectively. The first asteroid to be discovered, Ceres, was found in 1801
by Giuseppe Piazzi, and was originally considered to be a new planet. This was
followed by the discovery of other similar bodies, which, with the equipment of
the time, appeared to be points of light, like stars, showing little or no planetary
disc, though readily distinguishable from stars due to their apparent motions.
This prompted the astronomer Sir William Herschel to propose the term
"asteroid", coined in Greek as ἀστεροειδής asteroeidēs'star-like, star-shaped',
from Ancient Greek ἀστήρ astēr 'star, planet'. In the early second half of the
nineteenth century, the terms "asteroid" and "planet" (not always qualified as
"minor") were still used interchangeably; for example, the Annual of Scientific
Discovery for 1871, page 316, reads "Professor J. Watson has been awarded by
the Paris Academy of Sciences, the astronomical prize, Lalande foundation, for
the discovery of eight new asteroids in one year. The planet Lydia, discovered
by M. Borelly at the Marseilles Observatory had previously discovered two
planets bearing the numbers 91 and 99 in the system of asteroids revolving
between Mars and Jupiter". Near-Earth asteroids, or NEAs, are asteroids that
have orbits that pass close to that of Earth. Asteroids that actually cross the
Earth's orbital path are known as Earth-crossers. As of May 2010, 7,075 nearEarth asteroids are known and the number over one kilometre in diameter is
estimated to be 500–1,000.
Comets
Kuiper Belt
Before we start learning about the Kuiper Belt we need to know what is an A.U.
An A.U. or an Astronomical Unit is the distance from the Sun to the Earth i.e.
approximately 149,600,000 km.
The Kuiper Belt is a region of the solar system beyond the planets, extending
from the orbit of Neptune (at 30 AU) to approximately 50 AU from the Sun. It
is similar to the asteroid belt, but it is far larger—20 times as wide and 20 to
200 times as massive. Like the asteroid belt, it consists mainly of small bodies,
or remnants from the Solar System's formation. While most asteroids are
composed primarily of rock and metal, most Kuiper belt objects are composed
largely of frozen volatiles (termed "ices"), such as methane, ammonia and water.
The classical belt is home to at least three dwarf planets: Pluto, Haumea, and
Makemake. Some of the Solar System's moons, such as Neptune's Triton and
Saturn's Phoebe, are also believed to have originated in the region.
Since the belt was discovered in 1992, the number of known Kuiper belt objects
(KBOs) has increased to over a thousand, and more than 100,000 KBOs over
100 km (62 mi) in diameter are believed to exist. The Kuiper belt was initially
thought to be the main repository for periodic comets, those with orbits lasting
less than 200 years. However, studies since the mid-1990s have shown that the
classical belt is dynamically stable, and that comets' true place of origin is the
scattered disc, a dynamically active zone created by the outward motion of
Neptune 4.5 billion years ago; scattered disc objects such as Eris have
extremely eccentric orbits that take them as far as 100 AU from the Sun.
At its fullest extent, including its outlying regions, the Kuiper belt stretches
from roughly 30 to 55 AU. However, the main body of the belt is generally
accepted to extend from the 2:3 resonance (see below) at 39.5 AU to the 1:2
resonance at roughly 48 AU. The Kuiper belt is quite thick, with the main
concentration extending as much as ten degrees outside the ecliptic plane and a
more diffuse distribution of objects extending several times farther. Overall it
more resembles a torus or doughnut than a belt. Between the 2:3 and 1:2
resonances with Neptune, at approximately 42–48 AU, the gravitational
influence of Neptune is negligible, and objects can exist with their orbits
essentially unmolested. This region is known as the classical Kuiper belt, and its
members com Because the first modern KBO discovered, (15760) 1992 QB1, is
considered the prototype of this group, classical KBOs are often referred to as
cubewanos.
When an object's orbital period is an exact ratio of Neptune's (a situation
called a mean motion resonance), then it can become locked in a synchronised
motion with Neptune and avoid being perturbed away if their relative alignments
are appropriate. If, for instance, an object is in just the right kind of orbit so
that it orbits the Sun two times for every three Neptune orbits, and if it
reaches perihelion with Neptune a quarter of an orbit away from it, then
whenever it returns to perihelion, Neptune will always be in about the same
relative position as it began, since it will have completed 1½ orbits in the same
time. This is known as the 2:3 (or 3:2) resonance, and it corresponds to a
characteristic semi-major axis of about 39.4 AU. This 2:3 resonance is
populated by about 200 known objects, including Pluto together with its moons.
In recognition of this, the members of this family are known as plutinos. Many
plutinos, including Pluto, have orbits which cross that of Neptune, though their
resonance means they can never collide. Plutinos have high orbital eccentricities,
suggesting that they are not native to their current positions but were instead
thrown haphazardly into their orbits by the migrating Neptune. IAU guidelines
dictate that all plutinos must, like Pluto, be named for underworld deities. The
1:2 resonance (whose objects complete half an orbit for each of Neptune's)
corresponds to semi-major axes of ~47.7AU, and is sparsely populated. Its
residents are sometimes referred to as twotinos.
The 1:2 resonance appears to be an edge beyond which few objects are known.
It is not clear whether it is actually the outer edge of the classical belt or just
the beginning of a broad gap. Objects have been detected at the 2:5 resonance
at roughly 55 AU, well outside the classical belt; however, predictions of a large
number of bodies in classical orbits between these resonances have not been
verified through observation.
Earlier models of the Kuiper belt had suggested that the number of large
objects would increase by a factor of two beyond 50 AU, so this sudden drastic
falloff, known as the "Kuiper cliff", was completely unexpected, and its cause, to
date, is unknown. In 2003, Bernstein and Trilling et al. found evidence that the
rapid decline in objects of 100 km or more in radius beyond 50 AU is real, and
not due to observational bias.
Studies of the Kuiper belt since its discovery have generally indicated that its
members are primarily composed of ices: a mixture of light hydrocarbons (such
as methane), ammonia, and water ice, a composition they share with comets. The
low densities observed in those KBOs whose diameter is known, (less than 1 g
cm−3) is consistent with an icy makeup. The temperature of the belt is only
about 50K, so many compounds that would be gaseous closer to the Sun remain
solid.
Meteors, Meteoroids and Meteorites
Meteoroids are solid objects of a size considerably smaller than comets and
asteroids and are made up of rocks and minerals. Meteoroids travel at a very
high speed as they enter the Earth’s atmosphere. As the result of friction, they
burn and can be seen as a streak of light. This streak of light looks like a
shooting star (though it is not at all a star). We thus define this streak as a
Meteor. Meteors generally occur in the Mesosphere from 75 to 100 km.
Most meteoroids burn to ashes in a very short time, even before they reach the
lower atmosphere. However, some large meteoroids do not fully burn up and fall
on the Earth’s surface as solid pieces. These unburnt pieces of rocks that reach
the Earth’s surface are called Meteorites. They are capable of forming craters
on the surface of The Earth. Meteorites are considered to be very rare as they
are made up of very rare minerals, many of which are not even found on the
surface of the Earth.
Leonoid Meteor
Willamette Meteorite
The Sun
Planets and Our Moon
What is a planet? How many planets are there kin our Solar System?
Most of us grew up with the conventional definition of a planet as a body that
orbits a star, shines by reflecting the star's light and is larger than an asteroid.
Although the definition may not have been very precise, it clearly categorized
the bodies we knew at the time. In the 1990s, however, a remarkable series of
discoveries made it untenable. Beyond the orbit of Neptune, astronomers found
hundreds of icy worlds, some quite large, occupying a doughnut-shaped region
called the Kuiper belt. Around scores of other stars, they found other planets,
many of whose orbits look nothing like those in our solar system. They
discovered brown dwarfs, which blur the distinction between planet and star.
And they found planetlike objects drifting alone in the darkness of interstellar
space.
These findings ignited a debate about what a planet really is and led to the
decision last August by the International Astronomical Union (IAU),
astronomers' main professional society, to define a planet as an object that
orbits a star, is large enough to have settled into a round shape and, crucially,
"has cleared the neighborhood around its orbit." Controversially, the new
definition removes Pluto from the list of planets. Some astronomers said they
would refuse to use it and organized a protest petition.
There are 8 planets – Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and
Neptune.
What are dwarf planets? How many dwarf planets are there in our Solar
System?
A dwarf planet is a planetary-mass object that is neither a planet nor a
satellite. More explicitly, the International Astronomical Union (IAU) defines a
dwarf planet as a celestial body in direct orbit of the Sun that is massive
enough for its shape to be controlled by gravitation, but that unlike a planet has
not cleared its orbital region of other objects.
There are 5 dwarf planets in our Solar System – Pluto, Haumea, Makemake, Eris
and Ceres. Charon is called a dwarf planet by many of the scientists but the
IAU has not recognized it as a dwarf planet.
Sedna, Orcus, Quaoar, 2007 OR 10 are heavenly bodies which can be recognized
as dwarf planets.
Mercury
Mercury is the innermost planet in the Solar System. It is also the smallest, and
its orbit is the most eccentric (that is, the least perfectly circular) of the eight
planets.
It orbits the Sun once in about 88 Earth days, completing three rotations about
its axis for every two orbits. The planet is named after the Roman god Mercury,
the messenger to the gods. Mercury's surface is heavily cratered and similar in
appearance to Earth's Moon, indicating that it has been geologically inactive for
billions of years. Due to its near lack of an atmosphere to retain heat,
Mercury's surface experiences the steepest temperature gradient of all the
planets, ranging from a very cold 100 K at night to a very hot 700 K during the
day. Mercury's axis has the smallest tilt of any of the Solar System's planets,
but Mercury's orbital eccentricity is the largest. The seasons on the planet's
surface are caused by the variation of its distance from the Sun rather than by
the axial tilt, which is the main cause of seasons on Earth and other planets.
At perihelion, the intensity of sunlight on Mercury's surface is more than twice
the intensity at aphelion. Because the seasons of the planet are produced by the
orbital eccentricity instead of the axial tilt, the season does not differ between
its two hemispheres.
Because Mercury's orbit lies within Earth's orbit (as does Venus's), it can
appear in Earth's sky either as a morning star or an evening star. While Mercury
can appear as a very bright object when viewed from Earth, its proximity to the
Sun makes it more difficult to see than Venus. Mercury is one of
four terrestrial planets in the Solar System, and is a rocky body like the Earth.
It is the smallest planet in the Solar System, with an equatorial radius of
2,439.7 km. Mercury
is
even smaller—albeit
more
massive—than
the largest natural satellites in the Solar System, Ganymede and Titan. Mercury
consists of approximately 70% metallic and 30% silicate material. Mercury's
density is the second highest in the Solar System at 5.427 g/cm, only slightly
less than Earth's density of 5.515 g/cm. If the effect of gravitational
compression were to be factored out, the materials of which Mercury is made
would be denser, with an uncompressed density of 5.3 g/cm versus Earth's
4.4 g/cm. Mercury is the nearest planet to the sun. It is the second hottest
planet in the Solar System after its nearest neighbour – Venus.
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days.
The planet is named after the Roman goddess of love and beauty. After the
Moon, it is the brightest natural object in the night sky, reaching an apparent
magnitude of −4.6, bright enough to cast shadows. Because Venus is an inferior
planet from Earth, it never appears to venture far from the Sun: its elongation
reaches a maximum of 47.8°. Venus reaches its maximum brightness shortly
before sunrise or shortly after sunset, for which reason it has been referred to
by ancient cultures as the Morning Star or Evening Star.
Venus is classified as a terrestrial planet and is sometimes called Earth's
"sister planet" owing to their similar size, gravity, and bulk composition (Venus is
both the closest planet to Earth and the planet closest in size to Earth).
However, it has been shown to be very different from Earth in other respects.
Venus is shrouded by an opaque layer of highly reflective clouds of sulfuric acid,
preventing its surface from being seen from space in visible light. It has the
densest atmosphere of the four terrestrial planets, consisting mostly of carbon
dioxide. The atmospheric pressure at the planet's surface is 92 times that of
Earth's. With a mean surface temperature of 735 K (462 °C; 863 °F), Venus is
by far the hottest planet in the Solar System. It has no carbon cycle to lock
carbon back into rocks and surface features, nor does it seem to have any
organic life to absorb it in biomass. Venus may have possessed oceans in the
past, but these would have vaporized as the temperature rose due to the
runaway greenhouse effect. The water has most probably photodissociated, and,
because of the lack of a planetary magnetic field, the free hydrogen has been
swept into interplanetary space by the solar wind. Venus's surface is a dry
desertscape interspersed with slab-like rocks and periodically refreshed by
volcanism.
Venus is one of the four solar terrestrial planets, meaning that, like the Earth,
it is a rocky body. In size and mass, it is similar to the Earth, and is often
described as Earth's "sister" or "twin". The diameter of Venus is 12,092 km
(only 650 km less than the Earth's) and its mass is 81.5% of the Earth's.
Conditions on the Venusian surface differ radically from those on Earth, owing
to its dense carbon dioxide atmosphere. The mass of the atmosphere of Venus
is 96.5% carbon dioxide, with most of the remaining 3.5% being nitrogen. The
Venusian surface was a subject of speculation until some of its secrets were
revealed by planetary science in the 20th century. It was finally mapped in
detail by Project Magellan in 1990–91. The ground shows evidence of extensive
volcanism, and the sulfur in the atmosphere may indicate there have been some
recent eruptions.About 80% of the Venusian surface is covered by smooth,
volcanic plains, consisting of 70% plains with wrinkle ridges and 10% smooth or
lobate plains.
Venus
Earth
Earth is the third planet from the Sun, and eight planets in the Solar System.
It is also the largest of the Solar System's four terrestrial planets. It is
sometimes referred to as the world, the Blue Planet, or by its Latin name,
Terra. Earth formed approximately 4.54 billion years ago, and life appeared on
its surface within one billion years. Earth's biosphere then significantly altered
the atmospheric and other basic physical conditions, which enabled the
proliferation of organisms as well as the formation of the ozone layer, which
together with Earth's magnetic field blocked harmful solar radiation, and
permitted formerly ocean-confined life to move safely to land. The physical
properties of the Earth, as well as its geological history and orbit, have allowed
life to persist. Estimates on how much longer the planet will be able to continue
to support life range from 500 million years (myr), to as long as 2.3 billion years
Earth's lithosphere is divided into several rigid segments, or tectonic plates,
that migrate across the surface over periods of many millions of years. About
71% of the surface is covered by salt water oceans, with the remainder
consisting of continents and islands which together have many lakes and other
sources of water that contribute to the hydrosphere. Earth's poles are mostly
covered with ice that is the solid ice of the Antarctic ice sheet and the sea ice
that is the polar ice packs. The planet's interior remains active, with a solid iron
inner core, a liquid outer core that generates the magnetic field, and a thick
layer of relatively solid Earth gravitationally interacts with other objects in
space, especially the Sun and the Moon. During one orbit around the sun, the
Earth rotates about its own axis 366.26 times, creating 365.26 solar days, or
one sidereal. The Earth's axis of rotation is tilted 23.4° away from the
perpendicular of its orbital plane, producing seasonal variations on the planet's
surface with a period of one tropical year (365.24 solar days). The Moon is
Earth's only natural satellite. It began orbiting the Earth about4.53 billion
years ago. The Moon's gravitational interaction with Earth stimulates ocean
tides, stabilizes the axial tilt, and gradually slows the planet's rotation.
The planet is home to millions of species, including humans. Both the mineral
resources of the planet and the products of the biosphere contribute resources
that are used to support a global human population. The Earth's terrain varies
greatly from place to place. About 70.8% of the surface is covered by water,
with much of the continental sea level. This equates to 361.132 million km2
(139.43 million sq mi). The submerged surface has mountainous features,
including a globe- spanning mid-ocean ridgesystem, as well as undersea
volcanoes, oceanic trenches, submarine canyons, oceanic plateaus and abyssal
plains. The remaining 29.2% (148.94 million km2, or 57.51 million sq mi) not
covered by water consists of mountains, deserts, plains, plateaus, and other
geomorphologies. The planetary surface undergoes reshaping over geological
time periods due to tectonics and erosion. The surface features built up or
deformed through plate tectonics are subject to steady weathering from
precipitation, thermal cycles, and chemical effects. Glaciation, coastal erosion,
the build-up of coral reefs, and large meteorite impacts also act to reshape the
landscape.
The continental crust consists of lower density material such as the igneous
rocks granite andandesite. Less common is basalt, a denser volcanic rock that is
the primary constituent of the ocean floors. Sedimentary rock is formed from
the accumulation of sediment that becomes compacted together. Nearly 75% of
the continental surfaces are covered by sedimentary rocks, although they form
only about 5% of the crust. The third form of rock material found on Earth is
metamorphic rock, which is created from the transformation of pre-existing
rock types through high pressures, high temperatures, or both.
The most abundant silicate minerals on the Earth's surface include quartz, the
feldspars, amphibole, minerals include calcite(found in limestone) and dolomite.
The pedosphere is the outermost layer of the Earth that is soil and subject to
soil formation processes. It exists at the interface of the lithosphere,
atmosphere, hydrosphere and biosphere. Currently the total arable land is
13.31% of the land surface, with only 4.71% supporting permanent crops.
The Earth
Mars
Mars is the fourth planet from the Sun and the second smallest planet in the
Solar System. Named after the Roman god of war, it is often described as the
"Red Planet", as the iron oxide prevalent on its surface gives it a reddish
appearance. Mars is a terrestrial planet with a thin atmosphere, having surface
features reminiscent both of the impact craters of the Moon and the volcanoes,
valleys, deserts, and polar ice caps of Earth. The rotational period and seasonal
cycles of Mars are likewise similar to those of Earth, as is the tilt that
produces the seasons. Mars is the site of Olympus Mons, the second highest
known mountain within the Solar System (the tallest on a planet), and of Valles
Marineris, one of the largest canyons. The smooth Borealis basin in the northern
hemisphere covers 40% of the planet and may be a giant impact feature. Mars
has two known moons, Phobos and Deimos, which are small and irregularly
shaped. These may be captured asteroids, similar to 5261 Eureka, a Martian
trojan asteroid.
Until the first successful Mars flyby in 1965 by Mariner 4, many speculated
about the presence of liquid water on the planet's surface. This was based on
observed periodic variations in light and dark patches, particularly in the polar
latitudes, which appeared to be seas and continents; long, dark striations were
interpreted by some as irrigation channels for liquid water. These straight line
features were later explained as optical illusions, though geological evidence
gathered by unmanned missions suggest that Mars once had large-scale water
coverage on its surface. In 2005, radar data revealed the presence of large
quantities of water ice at the poles and at mid-latitudes. The Mars rover Spirit
sampled chemical compounds containing water molecules in March 2007. The
Phoenix lander directly sampled water ice in shallow Martian soil on July 31,
2008.
Mars is currently host to five functioning spacecraft: three in orbit – the Mars
Odyssey, Mars Express, and Mars Reconnaissance Orbiter; and two on the
surface – Mars Exploration Rover Opportunity and the Mars Science Laboratory
Curiosity. Defunct spacecraft on the surface include MER-A Spirit, and several
other inert landers and rovers, both successful and unsuccessful, such as the
Phoenix lander, which completed its mission in 2008. Observations by the Mars
Reconnaissance Orbiter have revealed possible flowing water during the
warmest months on Mars.
Mars can easily be seen from Earth with the naked eye. Its apparent magnitude
reaches −3.0, which is surpassed only by Jupiter, Venus, the Moon, and the Sun.
Optical ground-based telescopes are typically limited to resolving features
about 300 km (186 miles) across when Earth and Mars are closest, because of
Earth's atmosphere.
The current understanding of planetary habitability – the ability of a world to
develop and sustain life – favors planets that have liquid water on their surface.
This most often requires that the orbit of a planet lie within the habitable zone,
which for the Sun currently extends from just beyond Venus to about the semimajor axis of Mars. During perihelion, Mars dips inside this region, but the
planet's thin (low-pressure) atmosphere prevents liquid water from existing
over large regions for extended periods. The past flow of liquid water
demonstrates the planet's potential for habitability. Some recent evidence has
suggested that any water on the Martian surface may have been too salty and
acidic to support regular terrestrial life.
The lack of a magnetosphere and extremely thin atmosphere of Mars are a
challenge: the planet has little heat transfer across its surface, poor insulation
against bombardment of the solar wind and insufficient atmospheric pressure to
retain water in a liquid form (water instead sublimates to a gaseous state). Mars
is also nearly, or perhaps totally, geologically dead; the end of volcanic activity
has apparently stopped the recycling of chemicals and minerals between the
surface and interior of the planet.
Evidence suggests that the planet was once significantly more habitable than it
is today, but whether living organisms ever existed there remains unknown.
Mars lost its magnetosphere 4 billion years ago, so the solar wind interacts
directly with the Martian ionosphere, lowering the atmospheric density by
stripping away atoms from the outer layer. Both Mars Global Surveyor and Mars
Express have detected ionised atmospheric particles trailing off into space
behind Mars, and this atmospheric loss will be studied by the upcoming MAVEN
orbiter. Compared to Earth, the atmosphere of Mars is quite rarefied.
Mars
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet in the Solar
System. It is a gas giant with mass one-thousandth that of the Sun but is two
and a half times the mass of all the other planets in the Solar System combined.
Jupiter is classified as a gas giant along with Saturn, Uranus and Neptune.
Together, these four planets are sometimes referred to as the Jovian or outer
planets. The planet was known by astronomers of ancient times, and was
associated with the mythology and religious beliefs of many cultures. The
Romans named the planet after the Roman god Jupiter. When viewed from
Earth, Jupiter can reach an apparent magnitude of −2.94, making it on average
the third-brightest object in the night sky after the Moon and Venus. (Mars can
briefly match Jupiter's brightness at certain points in its orbit.)
Jupiter is primarily composed of hydrogen with a quarter of its mass being
helium, although helium only comprises about a tenth of the number of
molecules. It may also have a rocky core of heavier elements, but like the other
gas giants, Jupiter lacks a well-defined solid surface. Because of its rapid
rotation, the planet's shape is that of an oblate spheroid (it possesses a slight
but noticeable bulge around the equator). The outer atmosphere is visibly
segregated into several bands at different latitudes, resulting in turbulence and
storms along their interacting boundaries. A prominent result is the Great Red
Spot, a giant storm that is known to have existed since at least the 17th
century when it was first seen by telescope. Surrounding Jupiter is a faint
planetary ring system and a powerful magnetosphere. There are also at least 67
moons, including the four large moons called the Galilean moons that were first
discovered by Galileo Galilei in 1610. Ganymede, the largest of these moons, has
a diameter greater than that of the planet Mercury.
Jupiter has been explored on several occasions by robotic spacecraft, most
notably during the early Pioneer and Voyager flyby missions and later by the
Galileo orbiter. The most recent probe to visit Jupiter was the Pluto-bound New
Horizons spacecraft in late February 2007. The probe used the gravity from
Jupiter to increase its speed. Future targets for exploration in the Jovian
system include the possible ice-covered liquid ocean on the moon Europa.
Jupiter has the largest planetary atmosphere in the Solar System, spanning
over 5000 km in altitude. As Jupiter has no surface, the base of its atmosphere
is usually considered to be the point at which atmospheric pressure is equal to
10 bars, or ten times surface pressure on Earth.
Cassini Image of Jupiter
Saturn
Uranus
Neptune
Pluto
Eris
Ceres
Haumea
Makemake
Sedna
90842 Orcus
90482 Orcus is a trans-Neptunian object in the Kuiper belt with a large moon.
It was discovered on February 17, 2004 by Michael Brown of Caltech, Chad
Trujillo of the Gemini Observatory, and David Rabinowitz of Yale University.
Precovery images as early as November 8, 1951 were later identified. It is
believed to be a dwarf planet by some astronomers, and is massive enough to be
considered one under the 2006 draft proposal of the IAU, though the IAU has
not formally recognized it as such. Orcus is a plutino, locked in a 2:3 resonance
with Neptune, making two revolutions around the Sun, while Neptune makes
three. This is much like Pluto, except that it is constrained to always be in the
oppositephase of its orbit from Pluto: Orcus is at aphelion when Pluto is at
perihelion and vice versa. The surface of Orcus is relatively bright with albedo
reaching 30%, grey in color and water rich. The ice is predominantly in
crystalline form, which may be related to past cryovolcanic activity. Other
compounds likemethane or ammonia may also be present. The existence of a
satellite allowed astronomers to determine the mass of the system, which is
approximately equal to that of the Saturnian moon Tethys. Using observations
with the Hubble Space Telescope from November 13, 2005, Mike Brown and
T.A. Suer detected a satellite. The discovery of a satellite of Orcus was
reported in IAUC 8812 on 22 February 2007. The satellite was given the
designation S/2005 (90482) 1 before later being named Vanth. It orbits Orcus
in a nearly face-on circular orbit with aneccentricity of about 0.007, and an
orbital period of 9.54 days. Vanth orbits only 9030 ± 89 km from Orcus and is
too close to Orcus for ground-based spectroscopy to determine the surface
composition of the satellite.
The presence of crystalline water ice, and possibly ammonia ice may indicate
that a renewal mechanism was active in the past on the surface of Orcus.
Ammonia so far has not been detected on any TNO or icy satellite of the outer
planets other than Miranda. The 1.65 μm band on Orcus is broad and deep (12%),
as on Charon, Quaoar, Haumea, and icy satellites of giant planets. On the other
hand the crystalline water ice on the surfaces of TNOs should be completely
amorphized by the galactic and Solar radiation in about 10 million years. Some
calculations indicate that cryovolcanism, which is considered one of the possible
renewal mechanisms, may indeed be possible for TNOs larger than about 1000
km.[19] Orcus may have experienced at least one such episode in the past, which
turned the amorphous water ice on its surface into crystalline.
The preferred type of volcanism may have been explosive aqueous volcanism
driven by an explosive dissolution of methane from water–ammonia melts.
Models of internal heating via radioactive decay suggest that Orcus may be
capable of sustaining an internal ocean of liquid water. Using observations with
the Hubble Space Telescope from November 13, 2005, Mike Brown and T.A.
Suer detected a satellite. The discovery of a satellite of Orcus was reported in
IAUC 8812 on 22 February 2007. The satellite was given the designation
S/2005 (90482) 1 before later being named Vanth. It orbits Orcus in a nearly
face-on circular orbit with aneccentricity of about .007, and an orbital period of
9.54 days. Vanth orbits only 9030 ± 89 km from Orcus and is too close to Orcus
for ground-based spectroscopy to determine the surface composition of the
satellite.
Quaoar
Quaoar ("Kwawar") is a rocky trans-Neptunian object in the Kuiper belt with one
known moon. Several astronomers believe it to be a dwarf planet, and is massive
enough to be considered one under the 2006 draft proposal of the IAU, though
the IAU has not formally recognized it as such. Quaoar was discovered on June
4, 2002 by astronomers Chad Trujillo and Michael Brown at the California
Institute of Technology, from images acquired at the Samuel Oschin
Telescope at Palomar Observatory. The discovery of thismagnitude-18.5 object,
located in the constellation Ophiuchus, was announced on October 7, 2002, at a
meeting of theAmerican Astronomical Society. The earliest prediscovery
image proved to be a May 25, 1954 plate from Palomar Observatory. Quaoar is
named for the Tongva creator god, following International Astronomical
Union naming conventions for non-resonant Kuiper belt objects. The Tongva are
the native people of the area around Los Angeles, where the discovery of
Quaoar was made. Brown et al. had picked. The name with the more intuitive
spelling Kwawar, but the preferred spelling among the Tongva was Qua-o-ar. in
2004, Quaoar was estimated to have a diameter of 1260 ± 190 km, subsequently
revised downward, which at the time of discovery in 2002 made it the largest
object found in the Solar System since the discovery of Pluto. Quaoar was later
supplanted by Eris, Sedna, Haumea, and Makemake. Quaoar is about as massive
as (if somewhat smaller than) Pluto's moon Charon, which is approximately 2½
times as massive as Orcus. Quaoar is roughly one fifteenth the diameter
of Earth, one quarter the diameter of the Moon, and a third the size of Pluto.
Quaoar
was
the
first trans
Neptunian
object
to
be
measured directly from Hubble Space Telescope (HST) images, using a new,
sophisticated method. Given its distance Quaoar is on the limit of the HST
resolution (40 milliarcseconds) and its image is consequently "smeared" on a few
adjacent pixels. By comparing carefully this image with the images of stars in
the background and using a sophisticated model of HST optics (point spread
function (PSF)), Brown and Trujillo were able to find the best-fit disk size
which would give a similar blurred image. This method was recently applied by
the same authors to measure the size of Eris.
The uncorrected 2004 HST estimates only marginally agree with the
2007 infrared measurements by the Spitzer Space Telescope which suggest a
brighter albedo (0.19) and consequently a smaller diameter (844.4 +206.7
−
189.6 km). During the 2004 HST observations, little was known about the
surface properties of Kuiper belt objects, but we now know that the surface of
Quaoar is in many ways similar to those of the icy satellites of Uranus and
Neptune. Adopting a Uranian-satellite limb darkening profile suggests that the
2004 HST size estimate for Quaoar was approximately 40% too large, and that
a more proper estimate would be about 900 km. Using a weighted average of the
Spitzer and corrected HST estimates, Quaoar, as of 2010, can be estimated at
about 890 ± 70 km in diameter.
On 2011-05-04 Quaoar occulted a 16th-magnitude star, which gave 1170 km as
the longest chord and suggests an elongated shape.
Quaoar
2007 OR 10
Charon
Our Moon
The Earth has only one satellite, Luna or simply known as the Moon. The Moon is
the only natural satellite of the Earth, and the fifth largest satellite in the
Solar System. It is the largest natural satellite of a planet in the Solar System
relative to the size of its primary, having 27% the diameter and 60% the
density of Earth, resulting in 1⁄81 its mass. The Moon is the second densest
satellite after Io, a satellite of Jupiter.
The Moon is in synchronous rotation with Earth, always showing the same face
with its near side marked by dark volcanic maria that fill between the bright
ancient crustal highlands and the prominent impact craters. It is the brightest
object in the sky after the Sun, although its surface is actually very dark, with
a reflectance similar to that of coal. Its prominence in the sky and its regular
cycle of phases have, since ancient times, made the Moon an important cultural
influence on language, calendars, art and mythology. The Moon's gravitational
influence produces the ocean tides and the minute lengthening of the day. The
Moon's current orbital distance, about thirty times the diameter of the Earth,
causes it to appear almost the same size in the sky as the Sun, allowing it to
cover the Sun nearly precisely in total solar eclipses. This matching of apparent
visual size is a coincidence.
Surface of the Moon
Lunar Maria –
The lunar maria are large, dark, basaltic plains on Earth's Moon, formed by
ancient volcanic eruptions. They were dubbed maria, Latin for "seas", by early
astronomers who mistook them for actual seas. They are less reflective than
the "highlands" as a result of their iron-rich compositions, and hence appear
dark to the naked eye. The maria cover about 16 percent of the lunar surface,
mostly on the near-side visible from Earth. The few maria on the far-side are
much smaller, residing mostly in very large craters. The traditional
nomenclature for the Moon also includes one oceanus (ocean), as well as
features with the names lacus (lake), palus (marsh) and sinus (bay). The latter
three are smaller than maria, but have the same nature and characteristics.
Lunar Craters –
Lunar craters are craters on Earth's Moon. The Moon's surface is saturated
with craters, almost all of which were formed by impacts. The word crater
adopted by Galileo from the Greek word for vessel -. Galileo built his first
telescope in late 1609, and turned it to the Moon for the first time on
November 30, 1609. He discovered that, contrary to general opinion at that
time, the Moon was not a perfect sphere, but had both mountains and cup-like
depressions, the latter of which he gave the name craters.
Because of the Moon's lack of water, and atmosphere, or tectonic plates, there
is little erosion, and craters are found that exceed two billion years in age. The
age of large craters is determined by the number of smaller craters contained
within it, older craters generally accumulating more small, contained craters.
The smallest craters found have been microscopic in size, found in rocks
returned to Earth from the Moon. The largest crater called such is about 360
kilometers (220 mi) in diameter, located near the lunar South Pole.
Natural Satellites
Some Facts on Earth
1. The Earth is not exactly spherical; it is 42 kilometres wider than its height.
It is 12,756 kilometres wide and 12,714 kilometres tall!
2. Earth travels around the Sun at n oval-shaped orbit. That means 149.6 million
kilometers is its average distance from the Sun. The closest it gets to the Sun
is 147.million kilometers and the farthest it gets is 152.1 million kilometers!
3. A full 360-degree rotation of the Earth takes 23 hours, 56 minutes and 4.09
seconds!
4. The Earth spins on its axis at about 1,670 km/hour and rotates at 107,218
km/ hour!
5. Earth is tilted constantly toward the Sun at a 23.5- degree angle.
6. Earth’s weight is 5,972,000 billion billion kilograms. But the correct word
that should be used here is mass not weight get ready now for a class on mass!
Mass Class
Before we get into the subject of gravity and how it acts, it's important to
understand the difference between weight and mass.
We often use the terms "mass" and "weight" interchangeably in our daily
speech, but to an astronomer or a physicist they are completely different
things. The mass of a body is a measure of how much matter it contains. An
object with mass has a quality called inertia. If you shake an object like a stone
in your hand, you would notice that it takes a push to get it moving, and another
push to stop it again. If the stone is at rest, it wants to remain at rest. Once
you've got it moving, it wants to stay moving. This quality or "sluggishness" of
matter is its inertia. Mass is a measure of how much inertia an object displays.
Weight is an entirely different thing. Every object in the universe with mass
attracts every other object with mass. The amount of attraction depends on
the size of the masses and how far apart they are. For everyday-sized objects,
this gravitational pull is vanishingly small, but the pull between a very large
object, like the Earth, and another object, like you, can be easily measured.
How? All you have to do is stand on a scale! Scales measure the force of
attraction between you and the Earth. This force of attraction between you and
the Earth (or any other planet) is called your weight.
If you are in a spaceship far between the stars and you put a scale underneath
you, the scale would read zero. Your weight is zero. You are weightless. There is
an anvil floating next to you. It's also weightless. Are you or the anvil massless? Absolutely not. If you grabbed the anvil and tried to shake it, you would
have to push it to get it going and pull it to get it to stop. It still has inertia, and
hence mass, yet it has no weight. See the difference?
Now let’s study our weight in different parts of the Solar System.
Earth – 35 kg
Moon – 5.8 kg
Mercury - 13.2 kg
Venus – 31.7 kg
Mars – 13.1 kg
Jupiter – 82.7 kg
Saturn – 37.2 kg
Uranus – 31.1 kg
Io – 6.42 kg
Europa – 4.67 kg
Ganymede – 5.6 kg
Callisto – 4.42 kg
A White Dwarf – 45500000 kg
A Neutron Star – 4900000000000 kg
Orcus – 963 grams
Sedna – 1.78 kg
Neptune – 39.3 kg
Pluto – 2.3 kg
Sun – 947.5 kg
Space – 0 kg
Haumea – 1.56 kg
Quaoar – 1.78 kg
Ceres - 0.96 kg
Charon - 1 kg
Eris – 2.85 kg
Makemake – 1.7 kg
The situation in Space when objects can drift around is known as
weightlessness. You might think that there isn’t gravity in Space. But there is a
tiny amount of gravity called microgravity.
Unit 3 : Space Exploration
Rockets
What is a rocket?
A rocket is a missile, spacecraft, aircraft or other vehicle that obtains thrust
from a rocket engine. Rocket engine exhaust is formed entirely from propellants
carried within the rocket before use. Rocket engines work by action and
reaction. Rocket engines push rockets forward simply by throwing their exhaust
backwards extremely fast.
While comparatively inefficient for low speed use, rockets are relatively
lightweight and powerful, capable of generating large accelerations and of
attaining extremely high speeds with reasonable efficiency. Rockets are not
reliant on the atmosphere and work very well in space.
Who made the first rockets?
The Chinese made the first rockets about 1000 years ago but they were more
like fireworks than today’s space rockets. They were flaming arrows that were
fired from a basking using gunpowder.
When did the first liquid – fuel rocket fly?
In 1926, American Robert Goddard launched a 3.5 metre long rocket. It flew
about as high as a two – storey house, nowhere near outer space, and landed 56
metres away. The flight lasted just two and a half seconds.
Who built a rocket for war?
Wernher von Braun invented the V2, a rocket missile used by the Germans in
World War II. After the war, von Braun moved to the United States with the
new American space programme.
Why do we need rockets?
Rockets are important for space travel. They are the only achiness powerful
enough to launch things into space, such as satellites, probes and people.
Rockets have carried all the parts needed to build space stations up.
How fast can a rocket go?
To escape from Earth’s gravity, a rocket has to reach 40,000 kph – almost 20
times faster than Supersonic Concorde. Once it is out in the space, the rocket
drops down to around 29,000 kph to stay in orbit.
Why do rockets fall to pieces?
Rockets are made in stages, or pieces. Usually, there are three stages, made up
of the fuel tank, rocket engines and the sitting area where the astronauts sit
and work. The fuel tank contains fuel through which the rocket launches. After
this the fuel tank is dropped into the sea and is picked up by other astronauts.
The rocket boosters help the rockets to launch and boost up the rocket.
How do rocket engines work?
A rocket engine is not like a conventional engine. A conventional engine ignites
fuel which then pushes on some pistons, and it turns a crank. Therefore, it uses
rotational energy to turn the wheels of the vehicle. Electric motors also use
rotational energy to turn fans, and spin disks. A rocket engine does not use
rotational energy to run. They are reaction engines. The principle of it is that
the fuel contained within the body of the rocket goes through a chemical
reaction as it comes out of the end of the rocket. This reaction then causes
thrust and propels the rocket forward. This is an example of one of Sir Isaac
Newton's fundamental laws. "For every action, there is an equal and opposite
reaction"
Solid fuel rockets are the first rockets to be recorded in history. They were
first invented in ancient China, and have been used ever since (How Rocket
Engines Work.) The chemical make up of a solid rocket fuel is very similar to
the chemical makeup of gunpowder. However, the exact chemical make up is not
the same. To make a rocket work, a fast burning nonexclusive fuel is
needed. Gunpowder explodes, making it unusable. So the chemical composition
was altered to make it burn fast, but not explode. One of the biggest problems
with solid fuel rocket engines is that once started, the reaction cannot be
stopped or restarted. This makes them considered uncontrollable. Therefore,
solid fuel rockets are more widely used for missiles, or as booster rockets.
The first liquid fuel rocket was produced by Robert Goddard in 1926 (How
Rocket Engines Work.) The idea of liquid fueled rocket is easy to grasp. A fuel
and an oxidizer ,in Goddards case he used gasoline and liquid oxygen, are pumped
into a combustion chamber. A reaction takes place, and it expands propelling
the rocket forward. The expanding gas is then forced through a nozzle that
makes them accelerate to a higher velocity (How Rocket Engines Work.)
What is rocket fuel made of?
If you mean the stuff that is used in the giant fuel tank that is attached to a
departing space shuttle, then it is almost entirely liquid O2 (liquid oxygen).
Spacesuit
What Is a Spacesuit?
A spacesuit is more than clothes astronauts wear in space. The suit is really a
small spacecraft. It protects the astronaut from the dangers of being outside
in space.
Why Do Astronauts Need Spacesuits?
Spacesuits help astronauts in many ways. The suits protect astronauts from
getting too hot or cold. Spacesuits also give astronauts oxygen to breathe while
they are working in space. The suits hold water to drink. They also keep
astronauts from getting hurt by space dust. Space dust may not sound very
dangerous. But when it moves faster than a bullet, the dust can hurt someone.
The suits even have special gold-lined visors to protect eyes from bright
sunlight.
What Are the Parts of a Spacesuit?
A spacesuit is made up of many parts. One part covers the astronaut's chest.
Another part covers the arms and connects to the gloves. The helmet protects
the head. And the last part covers the astronaut's legs and feet. Some parts of
the suit are made of many layers of material. Each layer does something
different. Some keep oxygen in the suit while others protect astronauts from
space dust.
Under the suit, astronauts wear another piece of clothing. It covers their body
except for the head, hands and feet. Tubes are woven into it. Water flows
through the tubes to keep the astronaut cool.
On the back of the spacesuit is a backpack. The backpack holds oxygen so
astronauts can breathe. It also removes carbon dioxide that astronauts have
breathed out. The backpack also supplies electricity for the suit. A fan moves
the oxygen through the spacesuit. A water tank holds the cooling water.
Connected to the back of the suit is a tool called SAFER. SAFER has several
small thruster jets. If an astronaut floated away from the space station, he or
she could use SAFER to fly back.
Parts of a Spacesuit
NASA spacesuits have many pieces and parts. Learn about the parts and why
each piece is important.
Primary Life Support Subsystem
The PLSS is worn like a backpack. It provides astronauts
many of the things they need to survive on a spacewalk.
Its tanks supply oxygen for the astronauts to breathe.
It removes exhaled carbon dioxide. It contains a battery
for electrical power.
The PLSS also holds water-cooling equipment, a fan to
circulate oxygen and a two-way radio. A caution and
warning system in this backpack lets spacewalkers know
if something is wrong with the suit. The unit is covered
with protective cloth layers.
Upper Torso
The top of the spacesuit includes the Hard Upper Torso
and the arm assembly.
Hard Upper Torso
The HUT covers the chest and back. It is a vest made
out of fiberglass like some cars and swimming pools.
The Displays and Control Module and Primary Life
Support Subsystem attach to this piece. An important
function of this piece is that it serves as the
connection for the tubes that drain water and allow
oxygen flow.
Arms
Spacewalkers do not wear custom-made suits. Different sizes
of arm assembly parts are available. Sizing rings can make the
parts longer or shorter.
EVA Gloves
Astronauts must be able to work with and pick up objects
while wearing spacesuit gloves. EVA gloves protect
astronauts from the space environment. They are also
made so spacewalkers can move their fingers as easily as
possible. The fingers are the part of the body that gets
coldest in space. These gloves have heaters in the
fingertips. A piece called a bearing connects the glove to
the sleeve. The bearing allows the wrist to turn.
Displays and Control Module
This module is the control panel for the mini-spacecraft.
Switches, controls, gauges and an electronic display are
on the module. The astronaut can operate the Primary
Life Support Subsystem from this module.
In-Suit Drink Bag
A plastic, water-filled pouch attaches to the inside of
the Hard Upper Torso using Velcro. A plastic tube with a
valve sticks out of the bag. The tube and valve can be
adjusted to be near the astronaut's mouth. Biting the
valve opens the tube so the spacewalker can take a drink.
Releasing the bite closes the valve again.
Communications Carrier Assembly
The CCA is sometimes called the Snoopy Cap. The
astronaut wears the cap under the helmet. It has
earphones and microphones. It connects to the radio on
the spacesuit. Using the CCA, astronauts can talk with
the rest of the crew and hear the caution and warning
tones.
Helmet
Besides covering a spacewalker's head, the helmet has a
Vent Pad. This pad directs oxygen from the Primary Life
Support Subsystem and Hard Upper Torso to the front
of the helmet. The helmet keeps the oxygen at the right
pressure around the head. The main part of the helmet is
the clear plastic bubble.
The bubble is covered by the Extravehicular Visor
Assembly. The visor is coated with a thin layer of gold
that filters out the sun's harmful rays. The visor also
protects the spacewalker from extreme temperatures
and small objects that may hit the spacewalker.
A TV camera and lights can be attached to the helmet.
Lower Torso Assembly
This section is made up of spacesuit pants,
boots and the lower half of the waist
closure. A piece called the waist bearing
helps the astronaut move and turn. A metal
body-seal closure connects the lower torso
to the hard upper torso.
The lower torso has D-rings to attach
tethers. Tethers are the cords that attach
to the spacecraft so spacewalkers will not
float away.
Some suits are plain white; some have red
stripes; and others have candy cane stripes.
These variations help to tell one spacewalker
from another.
Liquid Cooling and Ventilation Garment
Most long underwear keeps people warm. This underwear
keeps spacewalkers cool. It is made of stretchy spandex
material. It has 91.5 meters, or 300 feet, of narrow
tubes throughout. Water is pumped through the tubes
near the spacewalker's skin. The chilled water removes
extra heat as it circulates around the crewmember's
entire body. The vents in the garment draw sweat away
from the astronaut's body. Sweat is recycled in the
water-cooling system. Oxygen is pulled in at the wrists
and ankles to help with circulation within the spacesuit.
Maximum Absorption Garment
Because spacewalks typically last more than six hours
without a break, spacewalkers wear adult-sized diapers
with extra absorption material under their spacesuits.
Simplified Aid for EVA Rescue
SAFER is like a life jacket. Spacewalkers working on the
space station wear SAFER. Astronauts are usually
connected to the station by a tether. If an astronaut
should become untethered and float away, SAFER would
help her or him fly back to the station. SAFER is worn
like a backpack. It uses small nitrogen-jet thrusters to
let an astronaut move around in space. Astronauts can
control SAFER with a small joystick.
Wrist Mirror
A spacewalker cannot see the front of the Displays and
Control Module while wearing the spacesuit. To see the
controls, astronauts wear a wrist mirror on the sleeve.
Look at the settings on the front of the module. They
are written backward. But "backward" is "forward" in a
mirror.
Layers
The spacesuit arm has 14 layers of material to protect
the spacewalker. The liquid cooling and ventilation
garment makes up the first three layers. On top of this
garment is the bladder layer. It creates the proper
pressure for the body. It also holds in the oxygen for
breathing. The next layer holds the bladder layer to the
correct shape around the astronaut's body and is made
of the same material as camping tents. The ripstop liner
is the tear-resistant layer. The next seven layers are
Mylar insulation and make the suit act like a thermos.
The layers keep the temperature from changing inside.
They also protect the spacewalker from being harmed by
small, high-speed objects flying through space. The outer
layer is made of a blend of three fabrics. One fabric is
waterproof. Another is the material used to make bulletproof vests. The third fabric is fire-resistant.
Cuff Checklist
On their wrists, astronauts wear a short checklist of the
tasks they will do during the spacewalk.
Safety Tethers
One end of these straps is attached to the spacewalker.
The other end is connected to the vehicle. The safety
tethers keep the astronauts from drifting away into
space.
Satellites
Space Exploration
Robotic Space Travel
A space probe is a robotic spacecraft that scientists send out on a journey
across the solar system in order to gather more information about our cosmic
neighbourhood. Robotic space missions aim to answer specific questions like
“What does the surface of Venus look alike?” “Is it windy on Neptune?” “What
is Jupiter made of?”
While robotic space missions are much less glamorous than manned space flight,
they have several big advantages :
1. Robots can travel for great distances, going farther and faster than any
astronaut. Like manned missions, they need a source of power – most use
solar arrays which convert sunlight to energy, but others which are
travelling long distances away from the Sun take their own on-board
generators. However, robotic spacecrafts need far less power than a
manned mission as they don’t need to maintain a comfortable living
environment on their journey.
2. Robots also don’t need supplies of food or water and they don’t need
oxygen to breathe, making them much smaller and lighter than a manned
mission.
3. Robots don’t get bored or homesick or fall ill on their journey.
4. If something goes wrong with a robotic mission, no lives are lost in space.
5. Space probes cost far less than a manned space flight and robots don’t
want to come home after their mission ends.
Space probes have opened up the wonders of the Solar System to us, sending
back data which has allowed scientists to understand far better how the Solar
System was formed and what conditions are like on other planets. While human
beings have to date travelled only as far as the Moon – a journey averaging
378,000 kilometers, space probes have covered billions of miles and shown us
extraordinary and detailed images of the far reaches of the Solar System.
In fact, almost 30 space probes reached the Moon before mankind did! Robotic
spacecrafts have now been sent to all the other planets in our Solar System,
they have caught the dust from a comet’s tail, landed on Mars and Venus and
travelled out beyond Pluto. Some space probes have even taken information
about our planet and the human race with them. Probes Pioneer 10 and Pioneer 11
carry engraved plaques with the image of a man and a woman on them and also a
map, showing where the probe came from. As the Pioneers journey onward into
deep space, they may one day encounter an alien civilization!
The Voyager probes took photographs of cities, landscapes and people of Earth
with them as well recorded greetings in many different Earth languages. In the
incredibly unlikely event of these probes being picked up by another civilization,
these greetings assure any aliens who manage to decode them that we are a
peaceful planet and we wish any other beings in our Universe well.
There are different types of space probes and the type used for a particular
mission will depend on the question that the probe is attempting to answer.
Some probes fly by the planets and take pictures for us, passing by several
planets on their long journey. Others orbit a specific planet to gain more
information about that planet and its moons. Another type of probe is designed
to land and send back data from the surface of another world. Some of these
are rovers, others remain fixed wherever they land.
The first rover, Lunokhod 1, was a part of a Russian probe, Luna 17, which
landed on the Moon in 1970. Lunokhod 1 was a robotic vehicle which could be
steered from Earth, in the same way as a remote control car.
NASA’s Mars landers, Viking 1 and Viking , which touched down on the Red
Planet in 1976, gave us our first pictures from the surface of the planet of
War, which have intrigued people on Earth for millennia. The Viking landers
showed the reddish-brown plains, scattered with rocks, the pink sky of Mars
and even frost on the ground in winter. Unfortunately, it is very difficult to land
on Mars and several probes sent to the red planet have crashed onto its
surface.
Later missions to Mars sent two rovers, Spirit and Opportunity. Designed to
drive around for at least three months, they lasted for far long and also, like
other spacecrafts sent to Mars, found evidence that Mars had been shaped by
the presence of water. In 2007, NASA sent the Phoenix Mission to Mar.
Phoenix could not drive around Mars but it had a robotic arm to dig into the soil
and collect samples. On board, it had a laboratory to examine the soil and work
out what it contains. Mars also has three operational orbiters around it – the
Mars Odyssey, Mars Express and Mars Reconnaissance Orbiter, showing us in
detail the surface features.
Robotic space probes have also shown us the hellish world that lies beneath the
thick atmosphere of Venus. Once it was thought that dense tropical forests
might lie under the Venusian clouds but space probes have revealed the high
temperatures, heavy carbon dioxide atmosphere and dark brown clouds of
sulphuric acid. In 1990, NASA’s Magellan entered orbit around Venus. Using
radar to penetrate the atmosphere, Magellan mapped the surface of Venus and
found 167 volcanoes larger than 70 miles wide! ESA’s Venus Express has been
into orbit around Venus since 2006. This mission is studying the atmosphere of
Venus and trying to find out how Earth and Venus developed in such different
ways. Several landers have returned information from the surface of Venus, a
tremendous achievement given the challenges of landing on this most hostile of
planets.
Robotic space probes have braved the scorched world of Mercury, a planet even
closer to the Sun than Venus. Mariner 10, which flew by Mercury in 1974 and
again in 1975, showed us that this bare little planet looks very similar to our
Moon. It is a grey, dead planet with very little atmosphere. In 2008, the
Messenger mission returned a space probe to Mercury and sent back the first
new pictures of the Sun’s nearest planet in 30 years.
Flying close to the Sun presents huge challenges for a robotic spacecraft but
probes sent to the Sun – Helios 1, Helios 2, SOHO, TRACE, RHESSI and others
have sent back information which helped scientists to develop a far better
understanding of the star at the very centre of our Solar System.
Further away in the Solar System, Jupiter was first seen in detail when the
probe Pioneer 10 flew by in 1973. Pictures captured by Pioneer 10 also showed
the Great Red Spot – a feature seen through telescopes from Earth for
centuries. After Pioneer, the Voyager probes revealed the surprising news
about Jupiter’s moons. Thanks to the Voyager probes, scientists on Earth learnt
that Jupiter’s moons are all very different to each other. In 1995, the Galileo
probe arrived at Jupiter and spent eight years investigating the giant gas planet
and its moons. Galileo was the first space probe to fly-by an asteroid, the first
to discover an asteroid and the first to measure Jupiter over a long period of
time. This amazing space probe also showed the volcanic activity on Jupiter’s
moon, Lo, and found Europa to be covered in thick ice, beneath which ay lie a
gigantic ocean which could even harbour some form of life!
NASA’s Cassini was not the first to visit Saturn – Pioneer 11 and the Voyager 1
and Voyager 2 had flown past on their long journey and sent back detailed
images of Saturn’s ring system and more information about the thick
atmosphere of Titan. But when Cassini arrived in 2004 after a 7 year journey, it
showed us many more features of Saturn and the moons that orbit it. Cassini
also released a probe, ESA’s Huygens, which travelled through the thick
atmosphere to land on the surface of Titan. The Huygens probe discovered that
Titan’s surface is covered in ice and and that methane rains down from the
dense clouds.
Even further from Earth, Voyager 2 flew by Uranus and showed pictures of this
frozen planet, tilted on its axis! Thanks to Voyager 2, we also know much more
about the thing rings circling Uranus, which are very different to the rings of
Saturn, as well as many details of its moons. Voyager 2 carried on to Neptune
and revealed this planet is very windy – Neptune has the fastest moving storms
in the Solar System. Voyager 2 is now 10 billion miles away from the Earth and
Voyager 1 is 11 billion miles away! They should be able to continue communicating
with us until 2020.
The Stardust mission – a probe which caught particles from a comet’s tail and
returned to us in 2006 – taught us far more about the very early Solar System
from these fragments. Capturing these samples from comets – which formed at
the centre of the Solar System but have travelled to its very edge – has helped
scientists to understand more about the origin of the Solar System itself!
Manned Space Flight
‘The Eagle has landed!’
This is the message US astronaut Neil Armstrong radioed back from the Moon
to mission control in Houston, US on 20 July 1969. The Eagle was the lunar
module, which had detached from the spacecraft Columbia, in orbit 60 miles
above the surface of the Moon. While astronaut Michael Collins remained on
board Columbia, the Lunar Excursion Module touched down on an area called the
Sea of Tranquility – but there was no water on the Moon so it didn’t land with a
splash. Neil Armstrong and Buzz Aldrin, the two astronauts inside the Eagle,
became the first humans ever to visit the Moon.
NASA
The National Aeronautics and Space Administration (NASA) is the agency of
the United States government that is responsible for the nation's civilian space
program and for aeronautics and aerospace research. Since February 2006,
NASA's mission statement has been to "pioneer the future in space exploration,
scientific discovery and aeronautics research."
President Eisenhower established the National Aeronautics and Space
Administration (NASA) in 1958 [6] with a distinctly civilian (rather than
military) orientation encouraging peaceful applications in space science. The
National Aeronautics and Space Act was passed on July 29, 1958, replacing its
predecessor, the National Advisory Committee for Aeronautics (NACA). The
agency became operational on October 1, 1958
Since that time, most U.S. space exploration efforts have been led by NASA,
including the Apollo moon-landing missions, the Skylab space station, and later
the Space Shuttle. Currently, NASA is supporting the International Space
Station and is overseeing the development of the Orion Multi-Purpose Crew
Vehicle and Commercial Crew vehicles. The agency is also responsible for the
Launch Services Program (LSP) which provides oversight of launch operations
and countdown management for unmanned NASA launches. Most recently, NASA
announced a new Space Launch System that it said would take the agency's
astronauts farther into space than ever before and provide the cornerstone for
future human space exploration efforts by the U.S.
National Aeronautics and Space Administration
The Appollo Mission
The Apollo program was one of the most expensive American scientific
programs ever. It is estimated to have cost $202 billion in present-day US
dollars. It used the Saturn rockets as launch vehicles, which were far bigger
than the rockets built for previous projects. The spacecraft was also bigger; it
had two main parts, the combined command and service module (CSM) and the
lunar landing module (LM). The LM was to be left on the Moon and only the
command module (CM) containing the three astronauts would eventually return
to Earth.
Buzz Aldrin on the moon, 1969
The second manned mission and the first to the Moon , Apollo 8, brought
astronauts for the first time in a flight around the Moon in December 1968.
Shortly before, the Soviets had sent an unmanned spacecraft around the Moon.
On the next two missions docking maneuvers that were needed for the Moon
landing were practiced and then finally the Moon landing was made on the Apollo
11 mission in July 1969.
The first person to stand on the Moon was Neil Armstrong, who was followed by
Buzz Aldrin while Michael Collins orbited above. Five subsequent Apollo missions
also landed astronauts on the Moon, the last in December 1972. Throughout
these six Apollo spaceflights, twelve men walked on the Moon. These missions
returned a wealth of scientific data and 381.7 kilograms (842 lb) of lunar
samples. Topics covered by experiments performed included soil mechanics,
meteoroids, seismology, heat flow, lunar ranging, magnetic fields, and solar wind.
The Moon landing marked the end of the space race and as a gesture,
Armstrong mentioned mankind when he stepped down on the Moon.
Skylab Project
Skylab was the United States' first and only independently built space station.
Conceived in 1965 as a workshop to be constructed in space from a spent Saturn
IB upper stage, the 169,950 lb (77,088 kg) station was constructed on Earth
and launched on May 14, 1973 atop the first two stages of a Saturn V, into a
235-nautical-mile (435 km) orbit inclined at 50° to the equator. Damaged during
launch by the loss of its thermal protection and one electricity-generating solar
panel, it was repaired to functionality by its first crew. It was occupied for a
total of 171 days by 3 successive crews in 1973 and 1974. It included a
laboratory for studying the effects of microgravity, and a solar observatory.
NASA planned to have a Space Shuttle dock with it, and elevate Skylab to a
higher safe altitude, but the Shuttle was not ready for flight before Skylab's
re-entry on July 11, 1979.
To save cost, NASA used one of the Saturn V rockets originally earmarked for
a canceled Apollo mission to launch the Skylab. Apollo spacecraft were used for
transporting astronauts to and from the Skylab. Three three-man crews stayed
aboard the station for periods of 28, 59, and 84 days. Skylab's habitable
volume was 11,290 cubic feet (320 m3), which was 30.7 times bigger than that
of the Apollo Command Module.
Skylab Project
Space Shuttle Program
The Space Shuttle became the major focus of NASA in the late 1970s and the
1980s. Planned as a frequently launchable and mostly reusable vehicle, four
space shuttle orbiters were built by 1985. The first to launch, Columbia, did so
on April 12, 1981, the 20th anniversary of the first space flight by Yuri Gagarin.
Its major components were a spaceplane orbiter with an external fuel tank and
two solid fuel launch rockets at its side. The external tank, which was bigger
than the spacecraft itself, was the only component that was not reused. The
shuttle could orbit in altitudes of 185–643 km (115–400 miles) and carry a
maximum payload (to low orbit) of 24,400 kg (54,000 lb). Missions could last
from 5 to 17 days and crews could be from 2 to 8 astronauts.
On 20 missions (1983–98) the Space Shuttle carried Spacelab, designed in
cooperation with the ESA. Spacelab was not designed for independent orbital
flight, but remained in the Shuttle's cargo bay as the astronauts entered and
left it through an airlock. Another famous series of missions were the launch
and later successful repair of the Hubble space telescope 1990 and 1993
In 1995 Russian-American interaction resumed with the Shuttle-Mir missions
(1995–1998). Once more an American vehicle docked with a Russian craft, this
time a full-fledged space station. This cooperation has continued with Russia
and the United States as the two of the biggest partners in the largest space
station built: the International Space Station (ISS). The strength of their
cooperation on this project was even more evident when NASA began relying on
Russian launch vehicles to service the ISS during the two-year grounding of the
shuttle fleet following the 2003 Space Shuttle Columbia disaster.
International Space Station
The International Space Station (ISS) combines the Japanese Kibō laboratory
with three space station projects, the Soviet/Russian Mir-2, the American
Freedom, and the European Columbus. Budget constraints led to the merger of
these projects into a single multi-national program in the early 1990s which is
managed by the five participating space agencies, NASA, the Russian RKA, the
Japanese JAXA, the European ESA, and the Canadian CSA. The station consists
of pressurized modules, external trusses, solar arrays and other components,
which have been launched by Russian Proton and Soyuz rockets, and the US
Space Shuttles. It is currently being assembled in Low Earth Orbit. The onorbit assembly began in 1998, the completion of the US Orbital Segment
occurred in 2011 and the completion of the Russian Orbital Segment is expected
by 2016. The ownership and use of the space station is established in
intergovernmental treaties and agreements which divide the station into two
areas and allow Russia to retain full ownership of the Russian Orbital Segment
(with the exception of Zarya), with the US Orbital Segment allocated between
the other international partners.
The STS-131 (light blue) and Expedition 23 (dark blue) crew members in April
2010.
Long duration missions to the ISS are referred to as ISS Expeditions.
Expedition crew members typically spend approximately six months on the ISS.
The initial expedition crew size was three, temporarily decreased to two
following the Columbia disaster. Since May 2009, expedition crew size has been
six crew members. Crew size is expected to be increased to seven, the number
the ISS was designed for, once the Commercial Crew Program becomes
operational. The ISS has been continuously occupied for the past 12 years and
113 days, having exceeded the previous record held by Mir; and has been visited
by astronauts and cosmonauts from 15 different nations.
The International Space Station, 2011
Hubble Space Telescope
The Hubble Space Telescope (HST) is a space telescope that was carried into
orbit by a Space Shuttle in 1990 and remains in operation. A 2.4-meter (7.9 ft)
aperture telescope in low Earth orbit, Hubble's four main instruments observe
in the near ultraviolet, visible, and near infrared. The telescope is named after
the astronomer Edwin Hubble.
Hubble's orbit outside the distortion of Earth's atmosphere allows it to take
extremely sharp images with almost no background light. Hubble's Deep Field
have been some of the most detailed visible-light images ever, allowing a deep
view into space and time. Many Hubble observations have led to breakthroughs
in astrophysics, such as accurately determining the rate of expansion of the
universe.
Although not the first space telescope, Hubble is one of the largest and most
versatile, and is well known as both a vital research tool and a public relations
boon for astronomy. The HST was built by the United States space agency
NASA, with contributions from the European Space Agency, and is operated by
the Space Telescope Science Institute. The HST is one of NASA's Great
Observatories, along with the Compton Gamma Ray Observatory, the Chandra Xray Observatory, and the Spitzer Space Telescope.
Space telescopes were proposed as early as 1923. Hubble was funded in the
1970s, with a proposed launch in 1983, but the project was beset by technical
delays, budget problems, and the Challenger disaster. When finally launched in
1990, scientists found that the main mirror had been ground incorrectly,
compromising the telescope's capabilities. The telescope was restored to its
intended quality by a servicing mission in 1993.
Hubble is the only telescope designed to be serviced in space by astronauts.
Between 1993 and 2002, four missions repaired, upgraded, and replaced
systems on the telescope; a fifth mission was canceled on safety grounds
following the Columbia disaster. However, after spirited public discussion,
NASA administrator Mike Griffin approved one final servicing mission,
completed in 2009 by Space Shuttle Atlantis. The telescope is now expected to
function until at least 2013. Its scientific successor, the James Webb Space
Telescope (JWST), is to be launched in 2018 or possibly later.
Hubble Space Telescope
Voyagers
The Voyager 1 spacecraft is a 722 kg (1,590 lb) space probe launched by NASA
on September 5, 1977 to study the outer Solar System and interstellar medium.
Operating for 35 years, 5 months and 6 days as of 25 February 2013, the
spacecraft receives routine commands and transmits data back to the Deep
Space Network. At a distance of about 123 AU (1.840×101011 km) as of
November 2012, it is the farthest human-made object from Earth. Voyager 1 is
now in the heliosheath, which is the outermost layer of the heliosphere. On
June 15, 2012, NASA scientists reported that Voyager 1 may be very close to
entering interstellar space and becoming the first human-made object to leave
the Solar System.
As part of the Voyager program, and like its sister craft Voyager 2, the
spacecraft is in extended mission, tasked with locating and studying the
boundaries of the Solar System, including the Kuiper belt, the heliosphere and
interstellar space.
It was the first probe to provide detailed images of the two largest planets and
their moons.
The Voyager 2 spacecraft is a 722 kg (1,590 lb) space probe launched by NASA
on August 20, 1977 to study the outer Solar System and eventually interstellar
space. It was actually launched before Voyager 1, but Voyager 1 moved faster
and eventually passed it. It has been operating for 35 years, 6 months and
5 days as of 25 February 2013, the spacecraft still receives and transmits data
via the Deep Space Network. At a distance of 100.675 AU (1.51×101011 km;
9.36×10911 mi) as of November 2012, it is one of the most distant manmade
objects (along with Voyager 1, Pioneer 10 and Pioneer 11).
Voyager 2
Explorers
The Explorer program is a United States space exploration program that
provides flight opportunities for physics, heliophysics, and astrophysics
investigations from space. Over 90 space missions have been launched since
1958, and it is still active. Starting with Explorer 6, it has been a NASA
program, and they have worked with a variety of other institutions and business,
including many international partners.
The Explorer program was the United States's first successful attempt to
launch an artificial satellite. It began as a U.S. Army proposal to place a
scientific satellite into orbit during the International Geophysical Year;
however, that proposal was rejected in favor of the U.S. Navy's Project
Vanguard. The Explorer program was later reestablished to catch up with the
Soviet Union after that nation's launch of Sputnik 1 on October 4, 1957.
Explorer 1 was launched January 31, 1958. Besides being the first U.S. satellite,
it is known for discovering the Van Allen radiation belt.
The Explorer program was transferred to NASA, which continued to use the
name for an ongoing series of relatively small space missions, typically an
artificial satellite with a science focus. Over the years, NASA has launched a
series of Explorer spacecraft carrying a wide variety of scientific
investigations.
Explorer satellites have made important discoveries: Earth's magnetosphere
and the shape of its gravity field; the solar wind; properties of micrometeoroids
raining down on the Earth; much about ultraviolet, cosmic, and X-rays from the
solar system and universe beyond; ionospheric physics; Solar plasma; solar
energetic particles; and atmospheric physics. These missions have also
investigated air density, radio astronomy, geodesy, and gamma ray astronomy.
Various space telescopes have made a variety of discoveries, including the first
known Earth Trojan asteroid.
The main satellites out of 92 satellites are listed here –
Explorer Missions
# Name(s)
Launch Date
Mission
End of Data
Re-Entry
1
Explorer
January 31, 1958
1
Energetic particle
studies, discovered
May 23, 1958
the Van Allen
radiation belt
2
Explorer
March 5, 1958
2
Failed to achieve
orbit
–
–
3
Explorer
March 26, 1958
3
Energetic particle
studies
June 27, 1958
June 27,
1958
March 31,
1970
4
Explorer
July 26, 1958
4
nuclear test studies October 5, 1958
October
23, 1959
5
Explorer
August 24, 1958
5
Failed to achieve
orbit
–
–
6
Explorer
August 7, 1959
6
Magnetosphere
research
October 6, 1959
July 1,
1961
7
Explorer
Energetic particle
October 13, 1959
7
studies
August 24, 1961
In orbit
Measured
Explorer
atmospheric
8
November 3, 1960
8
composition of the
ionosphere
December 27, 1960
March
27, 2012
Atmospheric
Explorer
9
February 16, 1961 density
9
measurements
April 9, 1964
April 9,
1964
10
Explorer
March 25, 1961
10
Investigated field
magnetic field
March 25, 1961
between the Earth
and Moon
11
Explorer
April 27, 1961
11
Gamma ray
astronomy
June 1,
1968
November 17, 1961 In orbit
Pioneers
The Pioneer program is a series of United States unmanned space missions that
was designed for planetary exploration. There were a number of such missions in
the program, but the most notable were Pioneer 10 and Pioneer 11, which
explored the outer planets and left the solar system. Each carries a golden
plaque, depicting a man and a woman and information about the origin and the
creators of the probes, should any extraterrestrials find them someday.
The Pioneer plaque attached to Pioneers 10 and 11
Pioneer 10 (originally designated Pioneer F) is a 258-kilogram robotic space
probe that completed the first mission to the planet Jupiter and became the
first spacecraft to achieve escape velocity from the Solar System. The project
was managed by the NASA Ames Research Center and the spacecraft was
constructed by TRW Inc. Pioneer 10 was assembled around a hexagonal bus with
a 2.74 m parabolic dish high-gain antenna oriented along the spin axis. Power was
supplied by four radioisotope thermoelectric generators that provided a
combined 155 W at the start of the mission.
Pioneer 10 was launched on March 2, 1972 by an Atlas-Centaur expendable
vehicle from Cape Canaveral, Florida. Between July 15, 1972, and February 15,
1973, it became the first spacecraft to traverse the asteroid belt. Imaging of
Jupiter began November 6, 1973, at a range of 25 million km, and a total of
more than 500 images were transmitted. The closest approach to the planet was
on December 4, 1973, at a range of 132,252 km. During the mission, the onboard instruments were used to study the asteroid belt, the environment
around Jupiter, solar wind, cosmic rays, and eventually the far reaches of the
solar system and heliosphere. Communication was lost on January 23, 2003, due
to power constraints, with the probe at a distance of 12 billion kilometers (80
AU) from Earth.
Pioneer 10
Pioneer 11 (also known as Pioneer G) is a 259-kilogram (569 lb) robotic space
probe launched by NASA on April 6, 1973 to study the asteroid belt, the
environment around Jupiter and Saturn, solar wind, cosmic rays, and eventually
the far reaches of the solar system and heliosphere. It was the first probe to
encounter Saturn and the second to fly through the asteroid belt and by
Jupiter. Due to power constraints and the vast distance to the probe,
communication has been lost since November 30, 1995.
Vikings
The Viking program comprised a pair of American space probes sent to Mars,
Viking 1 and Viking 2. Each spacecraft was composed of two main parts: an
orbiter designed to photograph the surface of Mars from orbit, and a lander
designed to study the planet from the surface. The orbiters also served as
communication relays for the landers once they touched down.
It was the most expensive and ambitious mission ever sent to Mars, with a total
cost of roughly US$1 billion. It was highly successful and formed most of the
body of knowledge about Mars through the late 1990s and early 2000s.
The Viking program grew from NASA's earlier, and more ambitious, Voyager
Mars program, which was not related to the successful Voyager deep space
probes of the late 1970s. Viking 1 was launched on August 20, 1975, and the
second craft, Viking 2, was launched on September 9, 1975, both riding atop
Titan III-E rockets with Centaur upper stages. Viking 1 entered Mars orbit on
June 19, 1976, with Viking 2 following suit on August 7.
After orbiting Mars for more than a month and returning images used for
landing site selection, the orbiters and landers detached; the landers then
entered the Martian atmosphere and soft-landed at the sites that had been
chosen. The Viking 1 lander touched down on the surface of Mars on July 20,
1976, and was joined by the Viking 2 lander on September 3. The orbiters
continued imaging and performing other scientific operations from orbit while
the landers deployed instruments on the surface.
Viking 1
Mariners
The Mariner program was a program conducted by the American space agency
NASA in conjunction with Jet Propulsion Laboratory (JPL) that launched a
series of robotic interplanetary probes designed to investigate Mars, Venus and
Mercury from 1962 to 1973. The program included a number of firsts, including
the first planetary flyby, the first pictures from another planet, the first
planetary orbiter, and the first gravity assist maneuver.
Of the ten vehicles in the Mariner series, seven were successful and three were
lost. The planned Mariner 11 and Mariner 12 vehicles evolved into Voyager 1 and
Voyager 2 of the Voyager program, while the Viking 1 and Viking 2 Mars orbiters
were enlarged versions of the Mariner 9 spacecraft. Other Mariner-based
spacecraft, launched since Voyager, included the Magellan probe to Venus, and
the Galileo probe to Jupiter. A second-generation Mariner spacecraft, called
the Mariner Mark II series, eventually evolved into the Cassini–Huygens probe,
now in orbit around Saturn.
Pathfinder and Sojourner
Mars Pathfinder (MESUR Pathfinder) was an American spacecraft that landed a
base station with a roving probe on Mars in 1997. It consisted of a lander,
renamed the Carl Sagan Memorial Station, and a lightweight (10.6 kg/23 lb)
wheeled robotic Mars rover named Sojourner.
Launched on December 4, 1996 by NASA aboard a Delta II booster a month
after the Mars Global Surveyor was launched, it landed on July 4, 1997 on
Mars's Ares Vallis, in a region called Chryse Planitia in the Oxia Palus
quadrangle. The lander then opened, exposing the rover which conducted many
experiments on the Martian surface. The mission carried a series of scientific
instruments to analyze the Martian atmosphere, climate, geology and the
composition of its rocks and soil. It was the second project from NASA's
Discovery Program, which promotes the use of low-cost spacecraft and frequent
launches under the motto "cheaper, faster and better" promoted by the then
administrator, Daniel Goldin. The mission was directed by the Jet Propulsion
Laboratory (JPL), a division of the California Institute of Technology,
responsible for NASA's Mars Exploration Program. The project manager was
JPL's Tony Spear.
This mission was the first of a series of missions to Mars that included rovers,
and was the first successful lander since the two Vikings landed on the red
planet in 1976. Although the Soviet Union successfully sent rovers to the Moon
as part of the Lunokhod program in the 1970s, its attempts to use rovers in its
Mars probe program failed.
Curiosity
Curiosity is a car-sized robotic rover exploring Gale Crater on Mars as part of
NASA's Mars Science Laboratory mission (MSL).
Curiosity was launched from Cape Canaveral on November 26, 2011, at 10:02
EST aboard the MSL spacecraft and successfully landed on Aeolis Palus in Gale
Crater on Mars on August 6, 2012, 05:17 UTC. The Bradbury Landing site was
less than 2.4 km (1.5 mi) from the center of the rover's touchdown target after
a 563,000,000 km (350,000,000 mi) journey.
The rover's goals include: investigation of the Martian climate and geology;
assessment of whether the selected field site inside Gale Crater has ever
offered environmental conditions favorable for microbial life, including
investigation of the role of water; and planetary habitability studies in
preparation for future human exploration.
Curiosity's design will serve as the basis for a planned unnamed 2020 Mars
rover mission. In December 2012, Curiosity's two-year mission was extended
indefinitely.
As established by the Mars Exploration Program, the main scientific goals of
the MSL mission are to help determine whether Mars could ever have supported
life, as well as determining the role of water, and to study the climate and
geology of Mars.The mission will also help prepare for human exploration. To
contribute to these goals, MSL has eight main scientific objectives:
Biological
(1) Determine the nature and inventory of organic carbon compounds
(2) Investigate the chemical building blocks of life (carbon, hydrogen, nitrogen,
oxygen, phosphorus, and sulfur)
(3) Identify features that may represent the effects of biological processes
(biosignatures)
Geological and geochemical
(4) Investigate the chemical, isotopic, and mineralogical composition of the
Martian surface and near-surface geological materials
(5) Interpret the processes that have formed and modified rocks and soils
Planetary process
(6) Assess long-timescale (i.e., 4-billion-year) Martian atmospheric evolution
processes
(7) Determine present state, distribution, and cycling of water and carbon
dioxide
Surface radiation
(8) Characterize the broad spectrum of surface radiation, including galactic
radiation, cosmic radiation, solar proton events and secondary neutrons
As part of its exploration, it also measured the radiation exposure in the
interior of the spacecraft as it traveled to Mars, and it is continuing radiation
measurements as it explores the surface of Mars. This data would be important
for a future manned mission.
Curiosity
Messenger
MESSENGER (an acronym of MErcury Surface, Space ENvironment,
GEochemistry, and Ranging) (also the name of the roman god it is named after)
is a robotic NASA spacecraft orbiting the planet Mercury, the first spacecraft
ever to do so. The 485-kilogram (1,070 lb) spacecraft was launched aboard a
Delta II rocket in August 2004 to study Mercury's chemical composition,
geology, and magnetic field. It became the second mission after 1975's Mariner
10 (launched by NASA on November 3, 1973) to reach Mercury successfully
when it made a flyby in January 2008, followed by a second flyby in October
2008, and a third flyby in September 2009.
The instruments carried by MESSENGER were tested on a complex series of
flybys – the spacecraft flew by Earth once, Venus twice, and Mercury itself
three times, allowing it to decelerate relative to Mercury using minimal fuel.
MESSENGER successfully entered Mercury's orbit on March 18, 2011, and
reactivated its science instruments on March 24, returning the first photo from
Mercury orbit on March 29. MESSENGER's formal data collection mission began
on April 4, 2011. On March 17, 2012, having collected close to 100,000 images,
MESSENGER ended its one-year primary mission and entered an extended
mission scheduled to last until March 2013.
During its stay in Mercury orbit, MESSENGER's instruments have yielded
significant data, including a characterization of Mercury's magnetic field and
the discovery of water ice at the planet's north pole.
Messenger Probe
Cassini - Huygens
Cassini–Huygens is a Flagship-class NASA-ESA-ASI robotic spacecraft sent to
the Saturn system. It has studied the planet and its many natural satellites
since arriving there in 2004, also observing Jupiter, the Heliosphere, and
testing the theory of relativity. Launched in 1997 after nearly two decades of
gestation, it includes a Saturn orbiter and an atmospheric probe/lander for the
moon Titan called Huygens, which entered and landed on Titan in 2005. Cassini is
the fourth space probe to visit Saturn and the first to enter orbit, and its
mission is ongoing as of 2013.
It launched on October 15, 1997 on a Titan IVB/Centaur and entered into orbit
around Saturn on July 1, 2004, after an interplanetary voyage which included
flybys of Earth, Venus, and Jupiter. On December 25, 2004, Huygens separated
from the orbiter at approximately 02:00 UTC. It reached Saturn's moon Titan
on January 14, 2005, when it entered Titan's atmosphere and descended to the
surface. It successfully returned data to Earth, using the orbiter as a relay.
This was the first landing ever accomplished in the outer Solar System.
Sixteen European countries and the United States make up the team
responsible for designing, building, flying and collecting data from the Cassini
orbiter and Huygens probe. The mission is managed by NASA’s Jet Propulsion
Laboratory in the United States, where the orbiter was assembled. Huygens was
developed by the European Space Research and Technology Centre, whose prime
contractor was Alcatel of France. Equipment and instruments for the probe
were supplied by many countries. The Italian Space Agency (ASI) provided the
Cassini probe's high-gain radio antenna, and a compact and lightweight radar,
which serves as a synthetic aperture radar, a radar altimeter, and a radiometer.
On April 16, 2008, NASA announced a two-year extension of the funding for
ground operations of this mission, at which point it was renamed to the Cassini
Equinox Mission. This was again extended in February 2010 with the Cassini
Solstice Mission continuing until 2017. The current end of mission plan is a 2017
controlled fall into Saturn's atmosphere. That same year, 2017, Juno will be deorbited by a crash into Jupiter.
Cassini – Huygens Probe
Juno
Juno is a NASA New Frontiers mission to the planet Jupiter. Juno was launched
from Cape Canaveral Air Force Station on August 5, 2011. The spacecraft is to
be placed in a polar orbit to study the planet's composition, gravity field,
magnetic field, and polar magnetosphere. Juno will also search for clues about
how Jupiter formed, including whether the planet has a rocky core, the amount
of water present within the deep atmosphere, and how the planet's mass is
distributed. It will also study Jupiter's deep winds, which can reach speeds of
618 kilometers per hour (384 mph).
The spacecraft's name comes from Greco-Roman mythology. The god Jupiter
drew a veil of clouds around himself to hide his mischief, but his wife, the
goddess Juno, was able to peer through the clouds and see Jupiter's true
nature.
Juno requires a five-year cruise to Jupiter, arriving around July 4, 2016. The
spacecraft will travel roughly over a total distance of 2.8 billion kilometers (18.7
AU; 1.74 billion miles). The spacecraft will orbit Jupiter 33 times during one
Earth year. Juno's trajectory will use a gravity assist speed boost from Earth,
accomplished through an Earth flyby two years (October 2013) after its August
5, 2011 launch. In 2016, the spacecraft will perform an orbit insertion burn to
slow the spacecraft enough to allow capture into an 11-day polar orbit. Once
Juno enters into its orbit, infrared and microwave instruments will begin to
measure the thermal radiation emanating from deep within Jupiter's
atmosphere. These observations will complement previous studies of the
planet's composition by assessing the abundance and distribution of water, and
therefore oxygen. While filling missing pieces of the puzzle of Jupiter's
composition, these data will also provide insight into the planet's origins. Juno
will also investigate the convection that drives general circulation patterns in
Jupiter's atmosphere. Meanwhile, other instruments aboard Juno will gather
data about the planet's gravitational field and polar magnetosphere. The Juno
mission is set to conclude in October 2017, after completing 33 orbits around
Jupiter, when the probe will be de-orbited to crash into Jupiter so as to avoid
any possibility of it impacting its moons.
Juno Probe, 2013
Galileo
Galileo was an unmanned NASA spacecraft which studied the planet Jupiter and
its moons, as well as several other solar system bodies. Named after
Renaissance astronomer Galileo Galilei, it consisted of an orbiter and entry
probe. It was launched on October 18, 1989, carried by Space Shuttle Atlantis
on the STS-34 mission. Galileo arrived at Jupiter on December 7, 1995, after
gravitational assist flybys of Venus and Earth, and became the first spacecraft
to orbit Jupiter. It launched the first probe into Jupiter, directly measuring its
atmosphere. Despite suffering major antenna problems, Galileo achieved the
first asteroid flyby, of 951 Gaspra, and discovered the first asteroid moon,
Dactyl, around 243 Ida. The total mission cost was about US$1.4 billion.
Jupiter's atmospheric composition and ammonia clouds were recorded, the
clouds possibly created by outflows from the lower depths of the atmosphere.
Io's volcanism and plasma interactions with Jupiter's atmosphere was also
recorded. The data Galileo collected supported the theory of a liquid ocean
under the icy surface of Europa, and there were indications of similar liquidsaltwater layers under the surfaces of Ganymede and Callisto. Ganymede was
shown to possess a magnetic field and the spacecraft found new evidence for
exospheres around Europa, Ganymede, and Callisto. Galileo also discovered that
Jupiter's faint ring system consists of dust from impacts on the four small
inner moons. The extent and structure of Jupiter's magnetosphere was also
mapped. In 1994, Galileo observed Comet Shoemaker-Levy 9's collision with
Jupiter.
On September 21, 2003, after 14 years in space and 8 years in the Jovian
system, Galileo's mission was terminated by sending the orbiter into Jupiter's
atmosphere at a speed of over 48 kilometres (30 mi) per second, reducing the
chance of contaminating local moons with terrestrial bacteria.
An artist’s impression of Galileo
Magellan
The Magellan spacecraft, also referred to as the Venus Radar Mapper, was a
1,035-kilogram (2,280 lb) robotic space probe launched by NASA on May 4,
1989, to map the surface of Venus using Synthetic Aperture Radar and measure
the planetary gravity. It was the first interplanetary mission to be launched
from the Space Shuttle, the first to use an inertial upper stage booster and was
the first spacecraft to test aerobraking as a method for circularizing an orbit.
Magellan was the fourth successful, NASA funded mission to Venus and ended
an eleven-year U.S. interplanetary exploration hiatus.
The objectives of the mission included:




Obtain near-global radar images of Venus' surface with a resolution
equivalent to optical imaging of 1 km per line pair. (primary)
Obtain a near-global topographic map with 50 km spatial and 100 m
vertical resolution.
Obtain near-global gravity field data with 700 km resolution and 2–3
milligals accuracy.
Develop an understanding of the geological structure of the planet,
including its density distribution and dynamics.
An artist’s impression of Magellan
Upcoming Missions
NASA Missions
ISRO Missions
Reusable Launch Vehicle-Technology Demonstrator (RLV-TD)
As a first step towards realizing a Two Stage To Orbit (TSTO) fully reusable launch vehicle, a series of technology demonstration missions have
been conceived. For this purpose a Winged Reusable Launch Vehicle
technology Demonstrator (RLV-TD) has been configured. The RLV-TD will
act as a flying test bed to evaluate various technologies viz., hypersonic
flight, autonomous landing, powered cruise flight and hypersonic flight
using air breathing propulsion. First in the series of demonstration trials
is the hypersonic flight experiment (HEX).
Human Space Flight Mission Programme
A study for undertaking human space flight to carry human beings to low
earth orbit and ensure their safe return has been made by the
department. The department has initiated pre-project activities to study
technical and managerial issues related to undertaking manned mission
with an aim to build and demonstrate the country’s capability. The
programme envisages the development of a fully autonomous orbital
vehicle carrying 2 or 3 crew members to about 300 km low earth orbit and
their safe return.
Space Science Missions
Chandrayaan-2
Chandrayaan-2, India’s second mission to the Moon, will have an Orbiter
and Lander-Rover module. ISRO will have the prime responsibility for the
Orbiter and Rover; Roskosmos, Russia will be responsible for Lander.
Chandrayaan-2 will be launched on India’s Geosynchronous Satellite Launch
Vehicle (GSLV-MkII). The science goals of the mission are to further
improve the understanding of the origin and evolution of the Moon using
instruments onboard Orbiter and in-situ analysis of lunar samples using
Lander and Rover.
Aditya-1
The First Indian space based Solar Coronagraph to study solar Corona in
visible and near IR bands. Launch of the Aditya mission is planned during
the next high solar activity period (2012-13) The main objectives is to
study the Coronal Mass Ejection (CME) and consequently the crucial
physical parameters for space weather such as the coronal magnetic field
structures, evolution of the coronal magnetic field etc. This will provide
completely new information on the velocity fields and their variability in
the inner corona having an important bearing on the unsolved problem of
heating of the corona would be obtained.
Topics to be done -
Universe – Introduction - Sanchit
What is a Solar System? - Jainil
Our Solar System - Jainil
Comets - Jainil
Sun – Jainil (include composition, future and structure)
Facts about Natural Satellites - Jainil
Satellites - Sanchit
Manned Missions - Prakhar
Constellations – Sanchit
Moon – Prakhar (include phases, tides, eclipses and
structure)
Saturn, Uranus, Neptune, Pluto, 2007 OR 10 – Sanchit
Charon, Haumea, Makemake, Eris, Ceres, Sedna - Jainil