UNIT 4 SPACE Chapter 30—STARS 30.3STELLAR EVOLUTION BASIC STRUCTURE
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Name:_____________________________
determines the star’s temperature, luminosity and size Larger stars have more mass, producing
temperatures in their core (due to
gravity’s pressure). Therefore, fusion reactions are faster, causing bigger stars to live
•
All stars are made of what elements?
–
73%
•
What force BALANCES the force of GRAVITY pulling in on the star?
, 25%
, 2%
_
lives!
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In stars of all sizes/life stages, something must exist to RESIST the force of
pushing in. LIFE CYCLE OF A STAR
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All stars begin as
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As the interstellar cloud collapses with gravity, it forms a
and then becomes
a (hot, condensed object)
•
When
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Once fusion begins in the core, a star continues to burn, converting the
finally begins, the star becomes stable.
into until the core has used up all its Hydrogen ➢ During this time, the star is a “ •
The
” Star
of the star shrinks once the Hydrogen is gone, while the surface
and then •
The star grows into a “
core becomes so hot that it fuses into
. ,” when
in the shrinking
DEATH OF STAR
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The next few phases of the life cycle depend on the star’s
POSSIBILITIES!):
(3
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1.) A smaller star (up to
the size of the Sun) will become a
_
once all the helium becomes carbon.
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The outer layers expand and are gradually lost. The shell of gas that remains is called a
“
–
In the core,
” (nothing to do with planets!). repel each other to maintain the star as gravity pulls
inward.
–
Eventually, the
dwarf cools into a
dwarf (which is
considered a dead star). •
2.) In larger stars (massive stars,
the sun’s size), Red Giants develop into
giants and eventually the finally, the force of _
core violently collapses in on itself as
overcomes the
pressure that has
been resisting it. •
This results in a massive explosion, or
, which produces all the
elements than iron, such as copper, uranium, silver and lead. ➢ Protons and electrons merge together to form
during this collapse.
➢ Neutrons resist collapse and the core becomes a dense
, which is
the end of the cycle for these "larger" stars.
•
3.) When a very highmass star (
greater than sun’s mass) collapses, the neutrons in the
core cannot support the collapse, and the core continues to collapse with gravity
•
This produces an EXTREMELY highgravity feature called a
.
.
REVIEW:
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All stars pass through a stage called a
when they run out of
hydrogen in the core and start fusing helium into carbon. •
When a small star finishes fusing its helium into carbon, it becomes a
. •
What force balances the gravity pulling in on a white dwarf? .
•
In the white dwarf phase, outer layers of gases are blown away. This shell of gas is called a
•
.
In a big star (Supergiant), when all that’s left in the core is IRON, the electrons cannot support the
force of gravity pulling in during the white dwarf phase. The collapse and subsequent massive explosion are called a ________________________________.
•
As outer layers of gas collide with the core, electrons and protons fuse to become neutrons, and a
form of dense degenerate matter arises. These stars are called________________ ________________.
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The Neutron Star (or Pulsar) is the end of the cycle unless a star is so massive that nothing (not even
neutrons) can support the collapse of the core. And then we have a: ______________ ______________. ➢ What’s Left After the Supernova ____________________ ____________________ (If mass of core 820’x Solar) Under collapse, protons and electrons combine to form neutrons (10 Km across) ____________________ ____________________ (If mass of core > 20 x Solar) Not even compacted neutrons can support weight of very massive stars.