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GEOGRAPHY
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ASTRONOMY AND SPACE SCIENCE
Universe encompasses everything; every possible
imagination. It is more than what we can know ever.
It a possible limit of every phenomenon in the senseperception of human being. Geographically, a universe
is defined as everything that physically exists:
the entirety of space and time, all forms of matter,
energy and momentum, and the physical laws and
constants that govern them. The present overall
densrty of the universe is very low, roughly 9.9 x
10-30 grams per cubic centimeter. This mass-energy
appears to consist of 73 per cent dark energy, 23 per
cent cold dark matter and 4 per cent ordinary matter.
Thus the density of atoms is on the order of a
single
hydrogen atom for every four cubic meters of volume.
The properties of dark energy and dark matter are
largely unknown. Dark matter gravitates as ordinary
matter, and thus works to slow the expansion of the
universe; by contrast, dark energy accelerates its
expansion.
Evolution of Space:
Geocentrie Theory: It was founded by Ptolemy in
140 A.D. It states that earth is at the centre of the
universe.
 Helio-centic Theory: It was propounded by
Copernicus in 1453 A.D. It states that all celestial body
revolves around the sun.
William Hersehel: It showed that sun is member
of galaxy, Milky Way and placed at one corner of
Milky Way.
Edwin Hubble (1925):He proved presence of other
galaxies. He also proved that galaxies are receding
constant from each other. With the help of analyzing
red shift (Doppler Effect), he also proved the rate at
which galaxies are receding.
Big Bang Theory:
It was put forth by Abbe George Lemaitre. It states
that receding movement of galaxies are result of
implosion. Big bang occurred at least 12 billion years
ago.
 Evidences:
discovery of background radiation proved by COBE,
cosmic background experiment, discovering uneven
ripple of microwave radiation, which suggests sudden
explosion.
Wormhole theory: According to a mind-bendingnew
theory, a blackhole is actually a tunnel between
universes-a type of wormhole.
The matter the black hole attracts doesn’t collapse in
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to a single point, as has been predicted, but rather
gushes out a “white hole” at the other end of the black
one, the theory goes. Wormhole theory is a potential
replacement for the Big Bang theory, which has
explained many of the conditions of our current
universe, but not all of them.
Scientist Nikodem Poplawski hopes that his
Wormhole theory will explain phenomena that are
currently inexplicable.
Wormhole theory states that our universe may not
have been created from a sudden explosion of matter
and energy (as the Big Bang theory posits), but that
rather that our universe was created when a large
planet in another universe collapsed in upon itself.
Advantages over big-bang theory: It is to be noted
that for some time, the Big Bang theory has been
struggling to explain’ dark energy’, and has also had
issues explaining how gravity interacts with
electromagnetism and nuclear forces. Wormhole
theory, on the other hand, might very well resolve
the problems of’ dark energy’ and the elusive nature
of gravity. While Wormhole theory has yet to be
stringently assessed and tested, it is nevertheless
an intriguing possibility.
Black-holes: It is extremely concentrated matter.
The pull of gravity is so powerful that nothing, not
even light, can comes out from it. So, black-hole can’t
be seen. Black-hole formation indicates ultimate
death of a star. The collapsing star core (due to
finishing up of fuel hydrogen), imparts much energy
to star exterior and explosion with very high luminosity
takes place. Mass less than about 1.4 times the mass
of the sun become a white dwarf.
Pulsating Theory: It goes beyond Big-Bang theory.
It says that receding nature of galaxy will not continue
forever, and gravity would ultimately stop expansion
and thereafter galaxy will collapse inward and
ultimately forming primordial substance once again.
Event Horizon: Rim of the black-hole from which
nothing could escape. Across event-horizon matter
and energy pass in only one direction. Event horizon
indicates beginning of black-holes.
Galaxies
Basically, a galaxy is a massive, gravitationally
bound system that consists of stars and stellar
remnants, an interstellar medium of gas dust, and
an important but poorly understood component
tentatively dubbed dark matters. The solar system
is in a galaxy called the Milky Way.
In 1965, American physicists Arno Penzias and
Robert Wilson detected faint radio waves throughout
the sky. According to the big bang theory, the waves
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are radiation left over from the initial explosion. The
strength of the radio waves appeared to be very
nearly the same in every direction. But in 1992, a
satellite called the Cosmic Background Explorer
(COBE) detected tiny differences in the strength of
radio waves coming from different directions.
Scientists estimate that there are more than 100
billion galaxies scattered throughout the visible
universe. Aristotle (384-322 BC) informs us in
Meteorologica (DK 59 ABO), the Greek philosophers
Anaxagoras (ca. 500-428 BC) and Democritus (450370 BC) proposed that the Milky Way might consist
of distant stars. Giant clusters of stars; our solarsystem · is part of galaxy called ‘Milky-Way.’
The stellar disk of the Milky Way galaxy is
approximately 100,000 light-years (9.5x1017 km) in
diameter, and is believed to be, on average, about
1,000 ly (9.5x1015 km) thick. A light year is the
distance that light travels in a vacuum in a year about 5.88 trillion miles (9 .46 trillion kilometers).
Galaxies range in diameter from a few thousand
to a half-million light-years. Small galaxies have fewer
than a billion stars. Large galaxies have more than
a trillion.
It is estimated to contain at least 200 billion stars
and possibly up to 400 billion stars, the exact
figure depending on the number of very lowmass stars, which is highly uncertain. The Galaxy
consists of a bar-shaped core region surround• ed by
a disk of gas, dust and stars forming four distinct
arm structures spiralling outward in a logarithmic
spiral shape.
It is extremely difficult to define the age at which
the Milky Way formed, but the age of the oldest star
in the Galaxy yet discovered, HE 1523-0901, is
estimated to be about 13.2 billion years, nearly as
old as the Universe itself. The most distant galaxies
ever photographed are as far as 10 billion to 13 billion
light-years away.
Only three galaxies outside the Milky Way are
visible with the unaided eye. People in the Northern
Hemisphere can see the Andromeda Galaxy, which
is about 2 million light-years away. People in the
Southern Hemisphere can see the Large Magellanic
Cloud, which is about 160,000 light years from
Earth, and the Small Magellanic Cloud, which is
about 180,000 light-years away. The Milky Way
and the Andromeda Galaxy are a binary system of
giant spiral galaxies belonging to a group of 50
closely bound galaxies known as the Local Group,
itself being part of the Virgo Super cluster.
Two smaller galaxies arid a number of dwarf
galaxies in the Local Group orbit the Milky Way.
The largest of these is the Large Magellanic Cloud
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with a diameter of 20,000 light-years. It has a close
companion, the Small Magellanic Cloud. The
Magellanic Stream is a peculiar streamer of neutral
hydrogen gas connecting these two small galaxies.
The stream is thought to have been dragged from
the Magellanic Clouds in tidal interactions with the
Galaxy. Some of the dwarf galaxies orbiting the
Milky Way are Canis Major Dwarf (the closest),
Sagittarius Dwarf Elliptical Galaxy, Ursa Minor Dwarf,
Sculptor Dwarf, Sextans Dwarf, Fornax Dwarf,
and Leo I Dwarf. All galaxies emit (give off) energy
as waves of visible light and other kinds of
electromagnetic radiation. In order of decreasing
wavelength (distance between successive wave
crests), electromagnetic radiation consists of radio
waves, infrared rays, visible light, ultraviolet rays,
X rays, and gamma rays. All these forms of radiation
together make up the electromagnetic spectrum.
A small percentage of galaxies called active galaxies
emit tremendous amounts of energy. This energy
results from violent events occurring in objects at
their center. The distribution of the wavelengths of
the emissions does not resemble that of normal stars,
and so the emissions are known as non-thermal
radiation. The most powerful such object is a
quasar, which emits a huge amount of radio, infrared,
ultraviolet, X-ray, and gamma-ray energy. Some
quasars emit 1,000 times as much energy as the
entire Milky Way, yet look like stars in photographs.
Quasar is short for quasi-stellar radio source. The
name comes from the fact that the first quasars
identified emit mostly radio energy and look much
like stars. A radio galaxy is related to, but appears
larger than, a quasar.
A Seyfert galaxy is a spiral galaxy that emits large
amounts of infrared rays as well as large amounts of
radio waves, X rays, or both radio waves and X
rays. Seyfert galaxies get their name from American
astronomer Carl K. Seyfert, who in 1943 became
the first person to discover one.
In a major development, the scientists have
discovered hundreds of galaxies just 250 million light
years away from earth which had been hidden
from view until now by Milky Way galaxy. Using
Commonwealth Scientific and Industrial Research
Organisation’s (CSIRO) Parkes radio telescope in
Australia equipped with an innovative receiver,
scientists were able to see through the stars and
dust of the Milky Way, into a previously unexplored
region of space. The discovery could help to explain
the mysterious gravitational anomaly dubbed the
Great Attractor, that appears to be drawing the Milky
Way and hundreds of thousands of other galaxies
towards it with a gravitational force equivalent to a
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million billion Suns. The research identified several
new structures that could help to explain the
movement of the Milky Way, including three galaxy
concentrations (named NWl, NW2 and NW3) and
two new clusters (named CWl and CW2). An
average gal• axy contains 100 billion stars, so finding
hundreds of new galaxies hidden behind the Milky
Way points to a lot of mass we didn’t know about
until now.
Types of galaxies: Galaxies are of two types: (i)
Regular Galaxies and (ii) Irregular Galaxies.
(i) Regular Galaxies: The regular galaxies may be of
either spiral or elliptical in shape.
(a) Spiral Galaxies: The Milky Way and the Great
Galaxy in Andromeda are illustrations of large spiral
galaxies, disc-shaped with greater concentration
of stats near their centers. The spiral galaxies have
cured spiral arms. About 25 % of all galaxies are well
supplied with the interstellar gas in which new bright,
young stars form. As the rotating spiral pattern sweeps
around the galaxy; it encompasses gas and dust,
triggering the formation of bright young stars in its
arms.
(b) Elliptical Galaxies: The most abundant are probably
the elliptical galaxies which are generally smaller
than their spiral counterparts. They are generally
symmetrical or spheroidal in shape with no obvious
structure. Most of their member stars are very old
and no new star forming in them. Some of them
are so small that the term ‘Dwarf’ has been
applied. The largest known elliptical galaxy is
200,000 light years in diameter. The biggest and the
brightest galaxies in the universe are elliptical with
masses of 1013 times that of our Sun. About 2/3rd
of all the galaxies are elliptical.
(ii) Irregular Galaxies: The irregular galaxies comprise
about 1/lOth of all galaxies and come in many subclasses. The stars of the irregular galaxies are generally
very old. Some of them have a mixture of the old
and new stars. The Milky Way and other spiral
galaxies consist of populations of old stars in the
centre, and the youngest stars situated in the arms.
Solar System
The Solar System consists of the Sun and those
celestial objects bound to it by gravity. These objects
are the eight planets, and their natural satellites (such
as our moon); dwarf planets; asteroids and comets.
Our solar system is located in an outward spiral of
the Milky Way galaxy. They called these objects
planets, meaning wanderers, and named them
after Roman deities - Jupiter, king of the gods; Mars,
the god of war; Mercury, messenger of the gods;
Venus, the goddess of love and beauty, and Saturn,
father of Jupiter and god of agriculture.
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Since the invention of the telescope, two more planets
have been discovered in our solar system: Uranus
(1781), Neptune (1846), and a dwarf planet Pluto
(1930). Pluto was reclassified as a dwarf planet in
2006. In addition, our solar system is populated by
thousands of small bodies such as asteroids and
comets. Most of the asteroids orbit in a region
between the orbits of Mars and Jupiter, while the
home of comets lies far beyond the orbit of Pluto,
in the Oort Cloud.
The four planets closest to the Sun - Mercury,
Venus, Earth, and Mars - are called the terrestrial
planets because they have solid rocky surfaces.
The four large planets beyond the orbit of Mars Jupiter, Saturn, Uranus, and Neptune - are called
the gas giants.
The small bodies include asteroids, icy Kuiper
belt objects, comets, meteoroids, and interplanetary
dust.
In order of their distances from the Sun, the
eight planets are: Mercury; Venus; Earth; Mars;
Jupiter; Saturn; Uranus; and Neptune; and Pluto
(now dwarf planet).
As of inid-2010, five smaller objects are classified as
dwarf planets. Ceres is in the asteroid belt, and four
orbit the Sun beyond Neptune: Pluto (formerly
classified as the ninth planet and now regarded as
dwarf planet), Haumea, Makemake, and Eris.
Nearly every planet - and some moons - has an
atmosphere. Earth’s atmosphere is primarily nitrogen
and oxygen. Venus has a thick atmosphere of carbon
dioxide, with traces of poisonous gases such as sulfur
dioxide. Mars’ carbon dioxide atmosphere is
extremely thin. Jupiter, Saturn, Uranus, and Neptune
are primarily hydrogen and helium. When Pluto is
near the Sun, it has a thin atmosphere, but when
Pluto travels to the outer regions of its orbit, the
atmosphere freezes and collapses to the planet’s
surface. In that way, Pluto acts like a comet.
There are about 170 known natural satellites (also
called moons) in orbit around the planets in our
solar system, ranging from bodies larger than our
own Moon to small pieces of debris. Many of these
were discovered by planetary spacecraft. Some of
moons have atmospheres (Saturn’s Titan); some
even have magnetic fields (jupiter’ s Ganymede).
Jupiter’s moon Io is the most volcanically active
body in the solar system. An ocean may lie
beneath the frozen crust of Jupiter’s moon Europa,
while images of Jupiter’s moon Ganymede show
historical motion of icy crustal plates. Some moons
may actually be asteroids that were captured by a
planet’s gravity. The captured asteroids presently
counted as moons may include Phobos and Deimos,
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several satellites of Jupiter, Saturn’s Phoebe, many
of Uranus’ new satellites, and possibly Neptune’s
Nereid.
I. Inner Solar System: The inner solar system
contains the Sun, Mercury, Venus, Earth and Mars.
The inner Solar System is the traditional name for
the region comprising the terrestrial planets and
asteroids. Composed mainly of silicates and
metals, the objects of the inner Solar System are
relatively close to the Sun; the radius of this entire
region is shorter than the distance between Jupiter
and Saturn.
Asteroid belt composed mainly of refractory rocky
and metallic minerals.
The main asteroid belt occupies the orbit between
Mars and Jupiter, between 2.3 and 3.3 AU from
the Sun. All asteroids save the largest, Ceres, are
classified as small Solar System bodies, but some
asteroids such as Vesta and Hygieia may be reclassed as dwarf planets if they are shown to
have achieved hydrostatic equilibrium.
Ceres: It is the largest body in the asteroid belt and
is classified as a dwarf planet.
Asteroid groups
Asteroids in the main belt are divided into asteroid
groups and families based on their orbital
characteristics. Asteroid moons are asteroids that
orbit larger asteroids.
Trojanasteroids are located in either of Jupiter’s
L4 or LS points (gravitationally stable regions leading
and trailing a planet in its orbit); the term “Trojan”
is also used for small bodies in any other planetary
or satellite Lagrange point.
Hilda asteroids are in a 2:3 resonances with Jupiter;
that is, they go around the Sun three times for every
two Jupiter orbits.
The inner Solar System is also dusted with rogue
asteroids, many of which cross the orbits of the
inner planets.
Earth is the largest of the inner planets.
II. Outer Solar System: It contains a higher
proportion of volatiles such as water, ammonia and
methane, than the rocky denizens of the inner
Solar System, as the colder temperatures allow these
compounds to remain solid.
The four outer planets, or gas giants (sometimes
called Jovian planets), col lectively make up 99 percent
of the mass known to orbit the Sun. It consists of
Jupiter and Saturn are each many tens of times the
mass of the Earth and consist overwhelmingly of
hydrogen and helium; Uranus and Neptune are far
less massive and possess more ices in their makeup.
Comet Hale-Bopp: Comets are small Solar System
bodies; short-period comets are believed to originate
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in the Kuiper belt, while long-period comets, such as
Hale-Bopp, are believed to originate in the Oort
cloud. Many comet groups, such as the Krentz
Sungrazers, formed from the breakup of a single
parent. Some comets with hyperbolic orbits may
originate outside the Solar System, but determining
their precise orbits is difficult.
III. Trans-N eptunianregion: This area is still
unexplored and nothing much is known. It consists
of Kuiper belt which extends between 30 and 50
AU from the Sun. The largest Kuiper belt objects,
such as Quaoar, Varuna, and Orcus, may be
reclassified as dwarf planets. Members of the classical
Kuiper belt are classified as cubewanos, after the
first of their kind to be discov• ered, (15760) 1992
QBl, and are still in near primordial, low-eccentricity
orbits.
Pluto and Charon: Charon, Pluto’s largest moon,
is sometimes described as part of a binary system
with Pluto, as the two bodies orbit a barycenter of
gravity above their surfaces (i.e., they appear to”
orbit each other”). Beyond Charon, two much
smaller moons, Nix and Hydra, orbit within the
system.
Haumea and Makemake: They are smaller than Pluto,
are the largest known objects in the classical Kuiper
belt. Haumea is an egg-shaped object with two
moons. Makemake is the brightest object in the
Kuiper belt after Pluto. The scattered disc, which
overlaps the Kuiper belt but extends much further
outwards, is thought to be the source of shortperiod comets. Scattered disc objects are believed
to have been ejected into erratic orbits by the
gravitational influence of Neptune’s early outward
migration. and are often almost perpendicular to it.
Eris is the largest known scattered disc object. It
has one moon, Dysnomia.
IV. Farthest regions: It is called heliopause and known
as the Sun’s Rochesphere. Oort cloud: The
hypothetical Oort cloud is a spherical cloud of up to
a trillion icy objects that is believed to be the source
for all long-period comets and to surround the Solar
System.
Sedna: It is a large, reddish Pluto-like object with a
gigantic, highly elliptical orbit.
The planets orbit the Sun in or near the same
plane, called the ecliptic. Pluto is a special case in
that its orbit is the most highly inclined (18 degrees)
and the most highly elliptical of all the planets.
 The vacuum of "space" comprises the
interplanetary medium. It includes various forms
of energy and at least two material components:
(a) interplanetary dust and (b) interplanetary gas.
Interplanetary dust consists of microscopic solid
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