This article got me thinking, can a planet hold a moon in orbit if it is just floating in the galaxy by itself not as part of a star system? Can a celestial body even qualify as a planet if it is floating around by itself?

  • 2
    $\begingroup$ Anything can orbit anything. This is just a mass question. $\endgroup$
    – Rory Alsop
    Dec 23 '13 at 18:41
  • 2
    $\begingroup$ @RoryAlsop Not even, you're such a hopeless traditionalist! :) :P $\endgroup$
    – TildalWave
    Dec 23 '13 at 19:07
  • $\begingroup$ @TidalWave this is extremely interesting, I too was a traditionalist until now $\endgroup$ Dec 23 '13 at 19:41

The answer is Yes.. Planets that don't orbit around a star are known as Rogue Planets. There is nothing preventing a rogue planet from having one or many moons.

Not so long ago, the first candidate for a free-floating exoplanet-exomoon system was presented in this paper. It looks like a gas giant several times larger than Jupiter with a sub-Earth mass moon.

Another study calculated and simulated scenarios where planets where ejected from their orbits around a star and concluded that around five percent of Earth-sized planets who are accompanied by Moon-sized natural satellites would retain them after the event.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.