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How Many Planets Can Orbit a Star?

-- | January 12, 2014

Question: How many planets a stellar-planetary system can accommodate safely into a stable orbit around that star? What are the factors it depends on?

For Example: Currently our solar system has 8 planets in a stable orbit. I want to know the maximum possible number of planets our system can accommodate so that added planets(beyond the orbit of Neptune) also follow the orbital pattern of 8 existing planets?
Suppose all the planets in our solar system are exact replica like Earth, then how many earth-like planets that our current sun can get hold off? — Vinod

Answer: With no other constraints on the star or the planets that orbit the star, the only requirement for stable orbits of planets around the star is that the total mass of the planets be less than the mass of the star. Therefore, one could in principal have a nearly infinite number of very small planets that orbit a star. In reality there are other constraints, such as merging of small planets that are near each other in the early phases of the formation of a planetary system, that reduces the final configuration of a planetary system. These additional constraints, though, conspire in a complex way to produce the final orbital configuration for an exoplanetary system.

Jeff Mangum

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