Although we know that HOT gas exists in our Galaxy, it
is very difficult to actually witness the “heating process”, since it is very
rapid and requires measurements that are beyond the current state of
space-borne instrumentation
It should be far easier to see how a hot gas COOLS !!
Although we normally expect things to cool by
conduction or convection, because hot interstellar gas is of such low density
the cooling takes place by emission of radiation.
