Chapter 16- Life of Stars Flashcards
what are the basic steps in a stars life
- competition between gravity and pressure
- thermal pressure
- radiation pressure
- turbulence
- rotation (centrifugal force)
first step of stars life
stars form a cold dense cloud of dust and gas called nebula
emission nebula
RED=HYDROGEN
- hydrogen atoms in these regions are ionized by high energy radiation =lost an electron
- this is how fluorescent lights work
Reflection Nebula
BLUE=DUST
- dust cloud surrounding newly formed stars
- dust scatters visible light causing it to be blue
Dark Nebula
BLACK
- cloud of dust and gas so dense that it blocks out background stars
- very little material there but cloud covers so much space
- the most promising site for new stars to form
what can astronomers determine from absorption spectrum lines
the composition of interstellar gas
molecular cloud
- most of the matter is molecules
- very very very cold
what causes the compression of molecular clouds
- spiral density waves in galaxies
- supernova explosion
- cloud collisions
in the third step, what does the cloud release
photons, therefore making it to become a protostar
more massive stars do what?
move to the main sequence faster
what would happen if the cloud were not able to radiate away its thermal energy
pressure would keep increasing
protostar
- often difficult to see in visible light because it still surrounded by cloud
- infrared light allows us to see through the cloud because it penetrates dust
what would happen to a protostar that formed without any rotation at all?
no rotation=no disk=no planets
final step in becoming a star
- temp and pressure become high enough for thermonuclear fusion t begin
- pressure balances gravity causing collapse to stop
smaller than ___ can’t sustain fusion
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