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Q&A: Supernova Remnants and Neutron Stars
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Q:
In your article about the possibility of RX J1856.5-3754 and
3C58 being quark stars, or at least containing some strange
quark matter it says that 3C58 is cooler than expected, so it is
thought it could be denser than a normal neutron star. Why would
something more dense be cooler?
A:
We think of dense objects as hot because of the heat
generated by compression. However, once compression is over,
a denser object will cool faster. The particles composing it
are closer together, collide more frequently, and radiate
away their energy more efficiently.
An everyday example is frost, which forms on the grass at
night. The grass, being denser than the air, cools faster
than the air at night, so a layer of frost can form on the
grass (which is an insulator and does not receive energy from
the Earth) even though the temperature of the air is above
freezing.
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