Rogue planet

This article is about planets not gravitationally bound to a star. For other uses, see Rogue planet (disambiguation).

A rogue planet, also termed a free-floating planet (FFP) or an isolated planetary-mass object (iPMO), is an interstellar object of planetary mass which is not gravitationally bound to any star or brown dwarf.

Rogue planets may originate from planetary systems in which they are formed and later ejected, or they can also form on their own, outside a planetary system. The Milky Way alone may have billions to trillions of rogue planets, a range the upcoming Nancy Grace Roman Space Telescope is expected to refine. The odds of a rogue planet entering the solar system, much less posing a direct threat to life on Earth, are slim to none with the odds being about one in one trillion within the next 1,000 years.

Some planetary-mass objects may have formed in a way similar to how stars form, and the International Astronomical Union has proposed that such objects be called sub-brown dwarfs. A possible example is Cha 110913−773444, which may have either been ejected and become a rogue planet or formed on its own to become a sub-brown dwarf.

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