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Planet X Found At Last?

For more than 100 years, astronomers have been searching for a mysterious object that lurks beyond Neptune and controls the orbits of distant bits of our solar system. Now, two professors think they’ve found it.

ByTim De ChantNOVA NextNOVA Next
ninth-planet-orbit
The orbit of Planet X (orange) is thought to influence the orbits of five objects seen here in blue.

For more than 100 years, astronomers have been searching for a mysterious object that lurks beyond Neptune and controls the orbits of distant bits of our solar system. Now, two professors think they’ve found it.

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Like earlier attempts to find Planet X, Michael Brown and Konstantin Batygin, both professors at Caltech, were trying to explain orbital anomalies. Unlike the others, who focused on large objects like Uranus, Brown and Batygin were studying six icy bodies that all exhibit oddly similar elliptical orbits. The chances of the coincidence, they said, are 1 in 14,000, and a very plausible explanation is a massive planet orbiting very, very far out.

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Here’s Nadia Drake, reporting for National Geographic:

“If there’s going to be another planet in the solar system, I think this is it,” says Greg Laughlin of the University of California, Santa Cruz. “It would be quite extraordinary if we had one. Fingers crossed. It would be amazing.”

The team calculated that the planet, if it’s there, would be about 10 times as massive as Earth, or roughly three times larger. That makes it a super-Earth or mini-Neptune—a type of planet the galaxy is incredibly efficient at assembling, but which has been conspicuously absent from our own neighborhood.

Despite the evidence Brown and Batygin present in their paper, no one is saying “mission accomplished.” Joel Achenbach and Rachel Feltman, reporting for the Washington Post, have more :

NASA’s director of planetary science, Jim Green, cautioned Wednesday that there could be other explanations for the observed motion of the small bodies in the outer solar system. He referenced the famous dictum from Carl Sagan that “extraordinary claims require extraordinary evidence.”

“The Sagan Rule applies. If it’s there, find it. I challenge you. Somebody out there oughta find it,” Green said.

Spotting Planet X with a telescope may be challenging, though. The 8-meter Subaru telescope in Hawaii could be up for the task, but its field of view can’t capture the entirety of the object’s likely orbit. Given that the object probably takes 10,000 to 20,000 years to complete an orbit around the sun, there’s a good chance we’ll miss it.

Even if it were to pass in front of the Subaru’s mirrors, it will take astronomers another five years to sift through the data for confirmation. But after more than a century of looking for Planet X, who’s counting?

Image credit: Caltech/R. Hurt (IPAC)