2. Galaxies- Large groups
of stars, dust and gas
Edwin Hubble classified 3
galaxies:
Spiral Galaxy- have a bulge at the
center and spiral arms
Ex. Our galaxy: Milky Way
3. What are two characteristics of spiral
galaxies? What makes up the arms of
a spiral galaxy?
Spiral galaxies have a bulge at
the center and spiral arms.
The arms of spiral galaxies are
made up of gas, dust and new
stars.
5. Contents of Galaxies
1. nebula- large clouds of duct
and gas
2. Star clusters
c. Globular cluster- group of
stars that look like a ball
d. Open cluster- group of stars
located along the spiral disk of
a galaxy
6. Origin of Galaxies
Quasars- star like sources of light
extremely far away
-maybe the core of young
galaxies that are forming
7. Formation of the
Universe
Cosmology- study of the origin,
structure and future of the
universe
Big Bang Theory- states the
universe began with a
tremendous explosion 13.7
billion years ago
8. How old is the universe?
1. Measure the distance from
earth to various galaxies
2. Calculate the ages of old,
nearby stars.
9. What will happen if the
expansion of the universe
continues forever?
Stars will age and die and the
universe will eventually become
cold and dark.
10. Chapter 20: Formation
of the Solar System
1. Solar system formed out of a vast
cloud of gas and dust called
nebula.
2. Nebula collapsed caused heating at
the center, planetisimals formed in
surrounding space
3. Central mass of nebula became
sun. planets formed from
surrounding materials.
11. The Sun: Our very own
star
Sun- a large ball of gas made
mostly of hydrogen (H) and
helium (He)
- sun’s energy comes from
nuclear fusion ( combination of
the nuclei of small atoms to
form a larger nucleus)
12.
13. Sunspots
Dark area cooler than the
surrounding areas and has
strong magnetic field
- Can affect earth’s
climate
14. Solar flares
- Giant eruptions on the sun’s
surface
- Can interact with
Earth’s atmosphere
15. Planetary Motion
Rotation- spin of a body on its
axis
Orbit- path a body follows as it
travels around another body in
space
Revolution- a body travels around
another body in space
