Planet Nine could really exist! New research suggests the putative world might orbit around the sun at an average distance of 600 astronomical units (AU).

Three years ago, Caltech astronomers Konstantin Batygin and Mike Brown announced their hypothesis for the existence of a ninth planet in our solar system. So, now they are publishing a pair of papers analyzing the evidence for Planet Nine’s existence.

Researchers have found patterns of objects in the Kuiper Belt that support the idea of the existence of Planet Nine. The way those objects clump together, suggests that gravity from something big out there is tugging on them.

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Observational evidence and computer-modeling work indicate that Planet Nine, also known as Planet X, Giant Planet Five or Planet Next, is perhaps 10 times more massive than Earth. And it probably travels along an elongated orbit that peaks at around 500 times Earth’s distance from the sun.

So, scientists now believe that Planet Nine is probably easier to spot than they had suspected.

“Perhaps counterintuitively, the increase in brightness due to a smaller heliocentric distance more than makes up for the decrease in brightness due to a slightly diminished physical radius, suggesting that Planet Nine is more readily discoverable by conventional optical surveys than previously thought,” Batygin and his colleagues wrote in the paper. Researchers have published their study online this month in the journal Physics Reports. You can read it for free at the online pre-print site

Credit: James Tuttle Keane/Caltech


The farthest object so far confirmed in the Solar System is FarFarOut, at 140 AU.

Some of the same authors of the Physics Report paper calculated the probability of Planet Nine not existing is around one in 500.

“Though this analysis does not say anything directly about whether Planet Nine is there, it does indicate that the hypothesis rests upon a solid foundation,” says Brown, the Richard and Barbara Rosenberg Professor of Planetary Astronomy.

However, astronomers are now making significant progress toward pinpointing the Planet Nine out in space.

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Thumbnail image: Artist’s illustration of the hypothetical Planet Nine, which may lie undiscovered in the outer solar system. Credit: Caltech/R. Hurt (IPAC)