How Many Planets Could Be in the Kuiper Belt?

A recent study published in The Astrophysical Journal Letters investigates the potential existence of Mars-sized free-floating planets (FFPs)—also known as rogue planets, starless planets, and wandering planets—that could have been captured by our Sun’s gravity long ago and orbit in the outer solar system approximately 1,400 astronomical units (AU) from the Sun. For context, the farthest known planetary body in the solar system is Pluto, which orbits approximately 39 AU from the Sun, and is also part of the Kuiper Belt, which scientists estimate extends as far out as 1,000 AU from the Sun.

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Planetary Mass Objects Discovered in Other Galaxies

In this artist's conception, a rogue planet drifts through space. Credit: Christine Pulliam (CfA)
In this artist's conception, a rogue planet drifts through space. Credit: Christine Pulliam (CfA)

A team of researchers at the University of Oklahoma have discovered “planetary mass bodies” outside of the Milky Way. They were discovered in one gravitationally-lensed galaxy, and in one gravitationally-lensed galaxy cluster using a technique called quasar micro-lensing. According to the researchers, the planetary mass objects are either planets or primordial black holes.

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