1. Astronomy Notes
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2. Stars The Sun An object made of gas that gives off energy
mainly hydrogen
helium
The Sun
medium in size & life span compared to other stars
primary energy source for all processes on Earth
much closer to Earth than any other star!
about 4 ½ billion years old

3. Magnitude = how bright/luminous
H-R Diagram: Shows the relationship between color, temperature, magnitude (brightness) & size of stars.
Color = temperature
Magnitude = how bright/luminous
Our Sun is a main sequence star.
Magnitude
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4. 2. Gravity pulls material into a sphere that becomes dense, hot
Black Dwarf
Iike our Sun!
Nebula
1. Large cloud of gas & dust where stars form.
2. Gravity pulls material into a sphere that becomes dense, hot
& ignites.
4. Outer layers come off
5. Collapses to just its core
3. Expands or
Explodes!
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5. Galaxy A large grouping of stars in space. 3 types
Spiral – bulge in center & distinctive spiral arms
Example: Our galaxy, The Milky Way
Our solar system is located within an arm
Elliptical – spherical or elongated
Irregular 1 2 3

6. Terrestrial Planet: a rocky, INNER planet
Our Solar System
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Terrestrial Planet: a rocky, INNER planet
Mercury
closest to the sun
no atmosphere
full of craters
very hot during day; freezing cold at night
Venus
Similar in size to Earth
Hot, thick & poisonous atmosphere
Earth – home!
Mars
known as the “red planet” because of its iron-rich soil

7. Gas Giant: large, OUTER planet that is made mostly of gases
Jupiter
largest planet
known for its storm, “The Great Red Spot”
Saturn
known for its ring system
Uranus
known for blue-green atmosphere
Neptune
blue-green atmosphere like Uranus
Also has a storm, “The Great Dark Spot”

8. Moon A natural satellite of a planet.
The outer planets have many of them!
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9. Other Rocky Bodies... Asteroids asteroid belt between Mars & Jupiter
small, rocky body that revolves around the Sun
Meteoroids – in space (like asteroids), but usually smaller
Meteors – (meteor shower); a bright streak of light caused by the rock burning as it streaks through the atmosphere
Meteorites – piece of rock that has landed on Earth without completely burning up, possibly making a crater
Comet – a body of ice, rock and dust that forms a tail as it gets close to the Sun
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10. Light Year
A measure of how long it takes light to travel through space in one year.
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11. Electromagnetic Spectrum
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Electromagnetic Spectrum
The range of all the waves that can travel through matter as well as empty space.
Scientists use different portions of the spectrum to learn about the universe.
Ex: light waves can tell us what elements stars are made & if they are moving away or towards other objects. R O Y G B I V
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12. Theories on the Origin of the Universe
Steady State – has always been the same
Oscillating Model - began by expanding, has slowed down & is now contracting
Big Bang - *the dominant theory
12 to 15 billion years ago
Universe began as a dense point that exploded
It rapidly expanded & began to cool down, forming stars, etc.
Evidence
discovery of cosmic background radiation
red shift in EM spectrum suggest it is still expanding
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