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Star Life (the end of it all)
A
damp squid or a vacuum cleaner from super-suction land
Have
you passed your Oppenheimer-Volkoff Limit?
What your fate
is, if you are a star, depends on how much stuff you have flung
out into space during the process of saying 'Goodbye!". A
small star has less material in the first place, and generally
ends up as a White Dwarf. Larger stars have more mass to play
with and gravity pulls what's left into denser Neutron Stars,
or even Black Holes.
The end result
actually depends on how massive the core is after all the explosions
have happened. If the material passes the Chandrasekhar
Limit of 1.4 times the Sun's mass, then the
White Dwarf stage is passed by and a Neutron Star is formed. However,
larger cores still, reaching over the Oppenheimer-Volkoff
Limit, which is more than 3 times the Sun's mass, collapse
further still to a Black Hole. Here's a guide to what does what
at the end of starlife:
|
Size
of Initial Star
|
As
fuel runs low, the star becomes a ...
|
In
the process of saying "Goodbye!" the star forms
a ...
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What's
Left
(in Sun's masses)
|
The
End
|
|
Small
|
Red
Giant
|
|
upto
1.4
|
|
| Medium |
Red
Supergiant
|
|
upto
3
|
|
| Big |
Red
Supergiant
|
Possible
Supernova
|
over
3
|
|
NOTE:
The values given in this table are not 'set in stone', they
can rise and fall, but you will not get back all the material
you put in. Remember, your star is at risk if you do not keep
up the thermal pressure required to keep it gravitationally
stable. Stellar evolution is protected by the laws of physics
as we know them.
Black
Hole
Some of these are areas of warped
space where an old dead star has collapsed in on itself to the
point where it's so dense that the escape velocity has increased
to beyond that of light. Technically that means nothing can
escape - no light can come out so it's 'black'. Because known
possible Black Holes are so far away not even the brainiest
of scientists know exactly what they are. Ideas include them
being a tiny point (smaller than you can imagine) with the sucking
power of a giant vacuum cleaner (bigger than you can imagine),
or they may be balls of strange dark energy which would pull
you down onto a bzarre hard surface where you would be shattered
into trillion of pieces of energy.
Neutron Star
There's not enough stuff in some
stars to collapse all the way down to a black hole when they
die. In this case they can become a Neutron Star: a ball of
very compressed matter about 20 kilometres in diameter. Rapidly
rotating Neutron Stars are known as Pulsars.
Supernova
The type of supernova caused
when a star finally gives up on trying to fight the forces of
gravity is known as a Type II supernova. It's caused by the
entire star collapsing down on to the core. This is like running
very fast into a brick wall (not recommended!),
and the shockwave this causes sends all the material above blasting
off in to space.
Planetary
Nebula
As a star begins to wobble towards
the end of its life its outer layers can be pushed out in various
circular patterns into space. The name 'planetary' comes from
their planet-like appearance in telescopes.
White
Dwarf
The remains of
a smaller star, like the Sun. These compact objects about the
size of the Earth shine only by radiating away their intense
heat. Eventually a White Dwarf will cool and end up as Black
Dwarf.
In
1862 Sirius B became the first White Dwarf to be discovered.
A handful of its matter would weigh 500 tonnes.
Some astronomers
believe that at the dead Black Dwarf stage of a White Dwarf
the star has become a diamond - the size of the Earth.
©
Anton Vamplew 2008
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