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 ...
|
What's
Left
(in Sun's masses)
|
The End
|
|
Small
|
Red Giant
|
|
upto 1.4
|
|
| Medium |
Red Supergiant
|
|
upto 3
|
|
| Big |
Red Supergiant
|
|
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.
The Cat's Eye
Planetary Nebula
|
