Take the 2-minute tour ×
Astronomy Stack Exchange is a question and answer site for astronomers and astrophysicists. It's 100% free, no registration required.

Planets form from disks of matter orbiting around a star as well as some moons form from disks of matter orbiting a planet. If this is going to happen, aproximately how much time will it take?

share|improve this question

2 Answers 2

up vote 13 down vote accepted

The answer to the headline question is: No. Most of Saturn's rings are below the Roche limit of about 2.5 Saturn radii. Hence tidal forces will prevent that part of the rings to form a (large) moon.

Actually, part of the rings may be caused by loss of material from some of Saturn's moons, as suspected from observations of Enceladus.

Accretion of Earth is still going on. So any number between millions of years and billions of years of accretion time for a planet can be justified. Half of Earth's mass should have accreted within 10 million years, see this paper.

share|improve this answer
Didn't know about the Roche limit, thank you –  Eduardo Serra Jan 23 at 0:53

It will not happen.

Existing moons have orbits that avoid these matter fragments to become bigger, by posing tidal forces into them.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

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