Asked in Stars
If red giants are cool stars why are they so bright?
Red giant stars emit less light per square meter of surface area than smaller, hotter stars, but their larger size means they have a larger surface area from which to emit light, so they emit more light overall. ...
Asked in Planetary Science, Planet Mars
Is Mars luminous or not?
It can be with the light it reflects from the sun, but not over long distances. Mars does not emit light except in the very long wavelengths (infra red). It is non-luminous. It is only visible because of the light it reflects, as the first answer states. ...