Download Intro to Astronomy

Introduction to Astronomy
I know nothing with any certainty but
the sight of stars makes me dream.
- Vincent Van Gogh
This is big to us.
Diameter of the Earth = 12,756 km
The farthest a human has traveled
from the Earth is the moon,
283,000 miles (452,000 km) during
the Apollo missions in the 1960’s
However…
and 70’s. This is 35 Earth
diameters away.
The difference
between
a bigger.
planet and a star involves their
The sun
is much
size. A planet is much smaller and shines only by reflecting
Diameter
ofstar
the is
sun
= 1,391,960
km its own light through
starlight. A
huge
and produces
a nuclear fusion
reaction.
( 109 Earths
across )
Distance from the Earth to the sun = 93,000,000 miles
( about traveled
100 solarbydiameters)
The farthest distance
an Earth spaceship
(unmanned) is Voyager 1, which is now about 105 A.U. It
was launched in 1970 and covers about 3.6 A.U. per year.
Pluto
Pluto
1 Astronomical
is 3,673,500,000
Unit ( km
1 A.U.)
from the sun.
150,000,000 km (=39.5
1 Earth-Sun
A.U.)
Distance
Astronomical units (A.U.s) are used to measure distances
between planets and their parent stars or other distances
within the local neighborhood of a solar system.
Light years
A light year is the distance light will travel in 1 year.
A light year is a unit used to describe the immense
distance between stars or galaxies. Stars are usually
trillions of miles apart. Galaxies are millions of times
further than that. Since light travels very quickly it can be
used to measure the huge distances.
Our sun is just another star. It is a little less than 8 light
minutes away the Earth. The stars we see at night only
look different to us because they are so much further
away. Most of them are many light years away.
Light years
A light year is the distance light will travel in 1 year.
1 year = 365 days x 24 hours x 60 minutes x 60 seconds
= 31,536,000 seconds
The speed of light is 300,000 kilometers per second.
So…...
1 light year is 9,460,000,000,000 kilometers
(approximately 1016 meters)
Our nearest neighboring star is 4 light years away.
37.8 trillion kilometers.
1 Light year = 63,133 A.U.
This would take 17,500 years in Voyager 1.
Our home galaxy, the Milky Way, is over 100,000 light
years across. This spiral galaxy looks similar to our own.
You are here.
It is home to over 200 billion stars… many are larger
than our sun. Each star represents its own solar system.
Our galaxy is called the Milky Way because on a dark
night, far away from city lights, you can see a band of stars
(and dust) stretching across the sky. Some think it
resembles a river of milk across the sky.
This is a picture of our galaxy
(from the inside, of course)
looking toward the center.
We cannot see our own galaxy from the outside because it
would take millions years in our fastest spaceship to leave
our galaxy so we could turn around and look back at it.
Spiral galaxy
Elliptical galaxy
Galaxies come in many different shapes and sizes but they
are all huge collections of billions of stars held together by
gravity.
Irregular galaxy
From an edge-on view a galaxy would appear very thin with
a central bulge and lanes of dust cutting across the middle.
Clusters of stars form a halo surrounding the central bulge.
There are billions of other galaxies visible from Earth.
This photo contains 10,000 of them and represents only
a tiny fraction of the sky.
As nebulas collapse due to
gravity new stars are created.
A galaxy is a massive collection of billions of stars
and clouds of gas and dust held together by gravity.
Stars may form in massive
clusters containing thousands
or millions of stars.
A nebula is a huge cloud of
gas and dust that may be lit
up by nearby stars. It is
where new stars may form.
Stars come in many sizes and colors. The color of the star
depends on its temperature.
Small, dim stars are the hard-to-see red stars.
The bright blue and white stars we see at night are the
largest and hottest stars in the galaxy.
Each star represents its own solar system.
Our sun is a medium-sized star. That
means its brightness and surface
temperature is average giving the sun
its yellow color.
Stars verses Planets
M
• A star produces its
own light and
generates power by
V E the
M process
J
of fusion
My Very Eager Mother Just
• A planet cannot
produce its own light
(it shines only
S
U and it N
reflected
light)
orbits another object.
Sent
Planets are much smaller
than stars. The main
difference between them
is their size. Bigger
means
Sunhotter.
Us
Nine
P
Pizzas
A solar system consists of a star (like our sun) and the
objects that orbit around it (planets and their moons, comets,
asteroids). Moons orbit planets and everything is held by the
sun’s gravity.
Comets are dirty snowballs the
Asteroids are large leftover
size of mountains that melt as
they fall toward the sun creating
long tails lit up by sunlight.
rocks (from boulder-sized to
mountain-sized) that orbit the
sun.
Some planets are small and rocky, called terrestrial.
These are like our home planet, Earth.
Other planets are huge and made mostly of layers of
gases, called gas giants. These, like Jupiter, were not
big or hot enough to become stars, but they are still
many time larger than the Earth.
Sizes
Galaxies
Stars
Planets
Moons
Asteroids
Comets
All energy travels in waves.
1 wavelength
Since the human eye can only see a tiny fraction of these
different wavelengths of electromagnetic energy,
scientists must create different tools to observe different
forms of energy traveling through the universe.
Types of Spectrum
can be used to identify elements in stars and nebula from across the
galaxy.
• Absorption spectrum has
certain wavelengths of light
absorbed leaving black lines
which act as a fingerprint.
Each element will absorb a
specific pattern of colors.
• Emission spectrum is created
when an element is heated to
the point it emits a certain
wavelength of light. Each
element emits a different
wavelength.
Spitzer Space Telescope
Neutrino
detector
Hubble Space Telescope
This Neutrino detector is located deep underground where all
other wavelengths of energy would be blocked. Neutrinos are
tiny particles created by stars. They are so small they can travel
right through normal matter, even through our entire planet.
Infra red (IR)
X-ray
Sonar
By studying different wavelengths of energy we can learn different
things about the universe around us.
Ultrasound
Ultraviolet (UV)
Magnetic
Resonance
Image (MRI)
By combining images from different
wavelengths of energy scientists can get a
more complete picture.
Space Exploration
•
•
•
•
•
Space exploration began with the launch of the Soviet spacecraft Sputnik Oct. 4,
1957.
Since then humans have orbited the Earth and walked on the moon (Apollo
missions). Now, the space shuttle is the primary spacecraft used to carry humans into
Earth orbit and bring satellites into space. The Space shuttle fleet of seven
spacecraft has conducted 120 missions, with two deadly accidents, and will be retired
in 2011 to make way for the next generation.
Hundreds of robotic spacecraft have been launched for many missions around our
solar system. Most of these do not return to the Earth.
Typically, spacecraft will use the gravity of the Earth or other planets to send them
farther out into space. The method is called “gravity assist” or “sling-shot”.
Otherwise, spacecraft would have to be much larger to carry enough fuel and more
powerful engines to get anywhere. Sling-shotting through space requires very precise
math calculations.
Within our solar system, spacecraft have explored all planets (except Pluto, although
one is on its way there), as well several comets and asteroids, the sun and our moon.
Important Robotic Spacecraft
• Mariner 10 (USA)
– Launched 11/3/1973 to explore Venus and Mercury
– First (only) spacecraft to explore Mercury. Only one side
of Mercury was visible.
– Mariner 10 still orbits the sun though all of its instruments
are dead.
• Magellan Space Probe (USA)
– Launched from the Space Shuttle 8/10/90 to explore
Venus
– Conducted extensive radar mapping of Venus surface
until it was deliberately crashed into the atmosphere of
Venus in 1994
• Galileo Spacecraft (USA)
– Launched 10/18/89 to explore Jupiter system
– Discovered an asteroid with a moon (Ida and
Dactyl) on its way
– Studied Jupiter, its moon and rings, witnessed a
comet, Shoemaker-Levi, colliding with Jupiter
– Mission ended when it was deliberately crashed
into Jupiter in 2003 (it reached a speed of 50
km/sec on its way down).
• Voyager 2 (USA)
– Launched 8/20/77 to explore all four gas giants
(Jupiter, Saturn, Uranus and Neptune)
– First (only) spacecraft to pass Uranus, 1986
– First (only) spacecraft to pass Neptune, 1989
– Still flying away, near the edge of the solar
system, it will run out of power by 2025, will
pass star Sirius in 295,000 years
• Cassini Spacecraft (joint
USA and European Mission)
– Launched 10/15/97 to explore Saturn system
– Tested Einstein’s Theory General Relativity, seeing
how time was altered by the gravity of the sun
– Arrived at Saturn 2004
– Huygens probe landed on moon Titan (only moon
besides the Earth that we have ever landed on)
– Cassini is still orbiting Saturn making close passes of
all of Saturn’s many moons and sending back high
resolution pictures
• Spitzer Space Telescope
– Launched 8/25/2003 to observe the universe at
infrared wavelengths
– Still orbiting the sun (heliocentric orbit) as it studies
distant objects.
• Hubble Space Telescope
– Launched from the space shuttle 4/24/90 to
observe the universe
– 10 year mission has lasted 19 years and still
working
– Primary mirror was seriously flawed and needed
to be repaired by a space shuttle mission. 3 other
servicing shuttle missions have kept the telescope
working and improving as it aged. There will be
no more missions to Hubble. Once it starts to
break down it will be deliberately crashed into the
ocean to prevent it from accidentally crashing
somewhere people might be hurt.
• Lunar Prospector
(NASA)
– Launched 1/7/1998
– Polar orbit of the moon
– It created a detailed map of the moon
and attempted to look for signs of
water ice in the rims of craters
– It was deliberately crashed into the
moon to try and throw ice crystals up
in the cloud created on impact
Sacrifices
• 3 astronauts died in fire during a prelaunch
test of Apollo 1 on Jan 27, 1967.
• 14 astronauts have died in two separate
accidents involving shuttle missions
causing NASA to be much more cautious
about the reasons for launching the
shuttle.
Challenger Shuttle
explodes after launch,
Jan. 28, 1986
Columbia Shuttle
disintegrates during
reentry of the
atmosphere, Feb. 1, 2003