In article , Brian Tung wrote:

A white dwarf is the hot exposed core of the progenitor star. As such,
it contains most of the heat that was in the star at the time that it
died. But the white dwarf radiates heat much slower than it did when
the star was alive, simply because its surface area is so much smaller.

Why does smaller surface area mean less radiation? If each particle is
radiating as much, what difference does it make how small a volume they
are contained in?

-- Richard