1.  Star is "born"-
    A.  Protostar
        1.  A star is "born" when the contracting gas and dust become so hot that nuclear fusion starts.
        2.  Fig. 11, pg. 803
2.  What does a stars life depend on?
    A.  How much mass it has.
        1.  Smaller stars live  longer 
            a.  they use up their fuel slower than larger stars
3.  Death of stars
    A.  Runs out of fuel and doesn't release enerby
        1.  center of star = shrinks
        2.  outer part = expands
    B.  Becomes a red giant or supergiant
    C.  all stars eventually become red giants or supergiants
    D.  fig. 12, pg. 804
    E.  What happens next depends on the mass of the star
        1.  When a star runs out of fuel it becomes
            a.  white dwarf ,
            b.  neutron star ,
            c.  or black hole

Summary

Left side
Draw exploring the lives of stars on pg. 805

1.  Our solar system
    A.  has one star
        1.  the sun
    B.  More than 1/2 of all stars are members of groups of stars
        1.  called star systems
    C.  Binary stars
        1.  Two stars
        2.  Example -Alpha Centuri A and B
    D.  Triple stars
        1.  3 stars
        2.  Example – Promixa Centuri
2. Galaxies
    A. Astronomers have classfied galaxies into 3 categories
        1.  spiral
        2.  irregular
        3.  elliptical
    B.  Fig. 17, pg. 810
3.  Spiral galaxy-
    A.  Our galaxy
    B.   Arms spiral outward like pinwheels
    C.  We are 2/3 out on one of the arms
4. Elliptical galaxy-
    A.  Flattened balls
    B.  No gas and dust= no new stars
    C.  Contain only old stars
5. Irregular galaxy-
    A. No regular patern or shape
    B.  Cloest irregular galaxy is Magellanic Cloud
        1.  160,000 light years away?

Summary

Left side
wksht.

1.  Astronomers have inferred that the universe is billions of years old
    A.  How?
        1.  light from other galaxies takes millions/billions of years to reach us
        2.  astronomers have photographed galaxies billions of years old

    B.  Galaxies are moving
    C.  Farther away a galaxy is from us, the faster it is moving away from us
    D.  Edwin Hubble discovered this
    E.  Fig. 19, 812
2.  Big Bang theory
    A. That is all it is - a theory, not proven, just thought
    B.  Universe formed in an enormous explosion about 10 to 15 billion years ago.
3.  Formation of the solar system
    A.  ~5 billion years ago a giant cloud of gas and dust or nebula collapsed to form the solar system
    B.  Fig. 20, pg. 813

Summary

Left Side
Section review pg. 814 #1-4