Can a habitable planet have mini-suns (i.e. solar satellites or glowing moons)?

Suns are stars. They are orbited by planets, and sometimes other stars. Planets are orbited by moons. Reasonably advanced civilizations may launch artificial satellites into orbits around their planet as well. Light and energy in a planetary system mostly come from its central star, which is powered by nuclear fusion of the lightest elements. Due to revolution of celestial bodies, planets often have regular seasonal and day-night cycles. Life that has developed on a planet depends on those cycles. I'd like to alter one of these fundamental concepts, making the system geocentric instead of heliocentric:

Would it be possible to have a star-like satellite orbiting a "class M" planet?
In other words, how can I light up a moon? (This seems to have been done before, but with handwaving/unobtainium, by Clarke in The Sands of Mars "Project Dawn" for Phobos and by Pohl/Kornbluth in Wolfbane.)

Since the discs of our Sun and Moon appear to be about the same size in the sky, imagine Moon would not reflect but emit light and possibly would revolve quicker around Earth ("1-day month").

This light-emitting moon would replace a proper sun, if orbiting a rogue planet, or would augment a sun that was too far away, i.e. the planet is outside any normal habitable zone of a usual planetary system.

An array of smaller satellites would also be acceptable and they may be artificial if necessary.

Problems

Regardless of energy source, I expect radiation to be a problem, even with a massive atmosphere.

Heliocentric systems are natural, because the smallest stars are still larger and more massive than the biggest planets: OGLE-TR-122b seems to be the smallest known star, which has about the size of Jupiter but 100 times its mass. The largest discovered exoplanets have 2 or 3 times the radius of Jupiter.

I think the large mass is required to make constant, stable hydrogen fusion possible. So that one is most likely not an option.

posted almost 9 years ago

Crissov‭

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