N eutron Stars Foreseen Supernova End Products When a supernova goes off we can speculate that The star might blow itself to smithereens scattering all its material into space and leaving ID: 560320
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Slide1
First, Consider the Possible Remnants:Neutron Stars Foreseen
Slide2
Supernova End Products?When a supernova goes off, we can speculate that:
The star might blow itself to smithereens,
scattering all its material into space and leaving
no remnant at all
;
or
Any leftover
central remnant
might collapse completely (into
a
‘
black hole
’
) because of gravity;
or
We might be left with
some bizarre remnant
at the
centre
(analogous to a white
dwarf)
.Slide3
New Physics?Remember that there are lots of very massive stars. Even after the outward explosion of a supernova, there may be a central lump left over that is more massive than the Chandrasekhar limit. Would it necessarily collapse under the influence of gravity?
Perhaps not: there
might be
some
‘
surprising new physics
’
that can forestall the intense gravity
and prevent the inward collapse of such a remnant.
If so, what would
the remnant’s properties be? Might it be detectable?Slide4
Neutron Stars!In the 1930s, theorists realized that an asteroid-sized ball
o
f
pure
neutrons
could resist the inward pull of gravity
,
thanks to neutron degeneracy. A cubic centimeter of such material would have a mass of more than a billion tons (the mass of a mountain). The density is 1012 to 1014 times the density of water.Slide5
A Neutron StarSuch an object would be a few kilometers in diameter (
the size
of Vancouver) but as
massive
as
a star. Slide6
The Interior Structure Slide7
Maybe Only In Principle?Theory tells us that massive stars
could
leave behind such remnants --
in principle.
But do they
actually do so?
The only way to be absolutely sure is to
find a neutron star.But this could be a real problem! Is there any way we could hope ever to detect a tiny object of this sort?Slide8
Can Neutron Stars be Detected?Even if blazing hot
, such tiny objects will be fantastically faint!
(They will also cool off quickly and fade away.)
Moreover, very
massive stars are quite rare; not many are close to us. (And that
’
s good! A nearby supernova would be a real danger!)
So a typical neutron star is likely to be hundreds, or maybe even thousands, of light years away. Slide9
By Contrast, White Dwarfs Are Easy!The white dwarfs, although
small, are
much bigger
than
n
eutron
stars.
They are also very common,so there are lots of themquite close to us (like thecompanion of Sirius, just 9light years away).Slide10
But We Are Saved! 1. The supernova creates the n
eutron star and throws
off
t
he stellar envelope, so the
c
entral remnant is exposed.
2. Morever, we can indeed detect the neutron stars that are formed, but not as hot embers. Instead, they call attention to themselves in a remarkable way
by acting as
pulsars
.