No planets are luminous in the sense that they produce their own light. Planets are celestial bodies that orbit a star and reflect the star's light.

Here's why:

* Planets do not have their own internal source of energy. They are not hot enough to undergo nuclear fusion, the process that powers stars and makes them luminous.

* They reflect light from their star. We see planets because their surfaces reflect the light of their host star. This reflected light is what makes them appear luminous to us.

Stars are the only celestial bodies that are truly luminous. They generate their own light and heat through nuclear fusion.