How Long Does a Star Live
    Depends of the mass
    The lower the mass
    The longer it lives
    Lives billions of years

    The higher the mass
        The more quickly it goes through the mass and dies
        Lives millions of years

Protostar
 

Contracting gas and dust  Hot enough to start nuclear fusion  large amounts of far infrared and microwave can be detected

   Main Sequence
 

a protostar starts burning hydrogen in its core      where its total mass determines all its structural properties          three divisions in a stellar interior are the nuclear burning core, convective zone and radiative zone          Stars begin their lives as 74% hydrogen, 25% helium and 1% everything else on the periodic table

    Fusion has been ongoing in the core of the Sun for 5 billion years,
        its core is now about 29% hydrogen, 70% helium and 1% everything else
        fusion process moves outward into a shell surrounding the hot helium core.
              continues creating more heavier elements

    Energy from the burning of hydrogen in the core.
            H-R -upper left part of the main sequence is populated by massive stars
                lower right part is populated by low-mass stars
 

spend the largest portion of their lives burning hydrogen in their cores              The central star of the Pistol Nebula -- one of the brightest and most massive main sequence stars known.

    Amount of mass
 

Large Mass Stars          stars that burn brightest, burn fastest and, thus, have the shortest lifetimes.          Millions of years to run out of hydrogen fuel

Small Mass Stars          low mass, cool star burns slow.          billions of years to run out of hydrogen fuel

 

Red Giants (low mass star)
 

star has run out of fuel       begins to cool, and contract.      outer layers of the star fall inwards under gravity          as they fall they heat up.      A shell becomes hot enough gaining a new source of energy.        core of the star is now hotter than it was      during its normal life           heat causes the outer parts  to swell.              becomes a giant.     outer layers then cool to only 3000 K      Common elements: carbon, nitrogen, oxygen          center - iron nuclei.

Super Giants
 

huge stars grow old      become even more enormous red supergiants (as their core fuses all the hydrogen into helium).      Their core shrinks, becoming hotter and denser.   fusion now produces heavier elements

Death of a star
    Running out of fuel

White Dwarfs
    loses most of its mass to the nebula.
    cools and shrinks; - only a few thousand miles in diameter!
    a stable star with no nuclear fuel. It radiates its left-over heat for billions of years.
        heat is all dispersed, - - a cold, dark black dwarf

Supernova
 

core shrinks, becoming hotter and denser.      Eventually core collapses (in an instant).      As the iron atoms are crushed together in this gravitational collapse,           the core temperature rises to about 100 billion degrees Celsius.      repulsive electrical forces between the atoms' nuclei overcomes the gravitational forces,          causing a massive, bright, short-lived explosion called a supernova.      During the explosion, shock waves, blow away the star's outer layers.  http://www.youtube.com/watch?v=S03vDKvva4g

Spitzer catches a supernova explosion 11,000 years ago
 

next stage depends on the star's remaining mass:
Neutron Star
    remaining mass is between 1 1/2 to 3 times the mass of the Sun
    collapse -small, dense - about ten miles in diameter
    about 1.4 times the mass of the Sun
    with an extraordinarily strong magnetic field, and rapid spin

Black Hole:
    remaining mass is greater than three times the mass of the Sun,
    the star contracts tremendously
    becomes incredibly dense
    with a gravitational field so strong that even light cannot escape

 
 http://www.space.com/common/media/video/player.php?videoRef=b050715_supernovadestroyer

A practice interactive on the lives of stars
http://www.ioncmaste.ca/homepage/resources/web_resources/CSA_Astro9/files/multimedia/unit2/star_lifecycle/star_lifecycle.swf

Discovery Channel video on lives of stars

Chandra X-ray Observatory:  LIfe cycle of stars