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Astronomy
https://www.youtube.com/watch?v=VOz4P
kdY7aA
How our Universe Formed
•Theory of how the universe formed called the
Big Bang Theory
•Big Bang Theory – the universe formed from a
massive expansion approximately 14 bya
The Universe is
expanding and the
visible edge is about
13.7 billion light
years away
The universe began billions of
years ago as a tiny dot that
exploded into today’s huge system
of stars and planets.
Support for the Big bang Theory
• Red shifts
• Cosmic background radiation
–Radio signals coming from every
direction in space.
–Believed to be created by the big
bang explosion.
The Expanding Universe
• 1929 – Edwin Hubble found that
the universe is expanding
– Estimated distances, relative brightness,
Doppler red shifts
Dimmer galaxies had greater red
shifts  farthest from Earth
https://www.youtube.com/watch?v=y5
tKC3nEx2I
Hubble’s Law: the more distant
Milky Way the
Galaxy…spiral
galaxies have greater red shifts,
shaped!
therefore they are moving away at
faster speeds.
Note: Our solar system is part of a bigger
system called a galaxy. Our galaxy (Milky Way)
is part of a bigger system called the universe
Milky Way
Galaxy…spiral
shaped!
Galaxies and Stars
Galaxies – billions of star groups
more than 100 billion galaxies, each containing
billions of stars
Milky Way
Galaxy…spiral
shaped!
So, how did our Solar System form?
•The Nebular Theory – explains that solar
system was formed from a rotating disk of
dust and gas
•Formed ~4.6 bya
1.Solar System began as a giant
ball of dust and gases (after the
Big Bang)
2.Cloud flattened as it spun
around, forming an accretion disk.
►Sun formed in the middle from all
the heat in the middle of the disk
3.Cooling of the disk caused small
shapes to form
4. These cool forms combined to
make the 4 SOLID inner planets
5.The lighter material combined
farther away, forming the 4
GASEOUS outer planets
Pluto
Neptune
Uranus
Mercury
Saturn
Jupiter
Mars
Earth
Venus
How Earth’s Formation Affected Earth
•Earth orbits the Sun following Kepler’s 3
laws of planetary motion
1. The path of each planet around the
Sun is an ellipse
2. Equal areas are covered in equal time
3. The length of time it takes a planet to
orbit the Sun is proportional to its
distance from the Sun
Kepler (15711630) came up
with these
scientific laws
and they are
still used in
Astronomy
today!
http://www.youtube.c
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1 Law: Law of Ellipses
The path of the
planets around
the sun are
elliptical in
shape with the
center of the sun
being located at
one focus
The shape of
the ellipse is
determined by
the location of
the two focus
points!
nd
2 Law: Law of Equal Areas
This law states that an imaginary line
from the sun to a planet sweeps out
equal areas in equal time intervals
nd
Kepler’s 2 Law of Planetary Motion
Are they the SAME?
• The short wide glass is holding the SAME amount of
water as the tall skinny glass!
Planet moves FASTER in orbit when
CLOSE to the SUN, and SLOWER in orbit
when FAR FROM the SUN
GRAVITATIONAL PULL
WHY?
Keppler’s 3rd Law
Do Now
1. What does eccentricity measure?
2. Ms. Sterling observed the orbital path of
Mars. From the data she collected, she found
the focal point length to be 10 light years and
the major axis length to be 22.5 light years.
Find Mars’ eccentricity based on her
observations.
3. Planet X has an eccentricity of 0.0803 and
Plant Y has an eccentricity of 0.8030. Using
these measurements explain the paths of
these planets around the sun.
The Sun
The sun is at the center of our solar system.
You may have learned that the planets orbit
the sun, but in fact the Sun and planets orbit
each other around the barycenter.
The Sun
•Our Sun and all other stars produce their
energy by a process called nuclear fusion
•Fusion is when hydrogen atoms collide to
make a Helium atom; this releases lots of
energy
Sun consumes
600 million tons
of H each second!
What is the Difference between Fusion and
Fission?
•Fission is the opposite idea…instead of
building bigger atoms, you are breaking
atoms apart
Nuclear Power Plants like
McGuire Nuclear Station in
Huntersville do this with
Uranium
Energy Produced
by the Sun
•Most of what
astronomers know
about our universe
is known from
studying the light
emitted from distant
sources
Electromagnetic Spectrum
• Visible light is just a small portion of the
energy emitted by stars…what else is there?
• Gamma Rays - are produced by violent nuclear explosions in
space and are absorbed by our atmosphere…good thing, they
are deadly to human cells!
• X-rays - are also absorbed by Earth’s atmosphere, so NASA has
to put x-ray telescopes into space
• UV Rays - are mostly blocked by the ozone layer, but some can
get through and cause sunburns!
• Infrared Rays - cause the heat we feel from sunlight
• Microwaves - easily move through atmosphere and are used in
with satellites and GPS
• Radio Waves - are used with huge telescopes to learn about the
structure, composition, and motion of objects in space
The Electromagnetic Spectrum