Jupiter is known to radiate more light than it receives from the sun,
but it's mostly in the far infrared. It hasn't completely cooled down
from its birth pangs...

ANY planet that net radiates into its environment, thereby cooling
down, is "luminous". For example, Earth. It's just that the luminosity
may not be in the visible range of wavelengths.

"luminous" needs to be better defined.

I'm sure that every planet (and probably every moon) in out solar system
is "luminous" in that it radiates more mid-to-far IR than it receives,
and that it's still cooling down.


Martin
--
M.A.Poyser Tel.: 07967 110890
Manchester, U.K. http://www.livejournal.com/userinfo.bml?user=fleetie