UC Berkeley astronomers provide support for existence of ‘Planet Nine’

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UC Berkeley researchers have detected the orbital motion of an exoplanet discovered in 2013 known as HD 106906 b.

These findings, published in The Astronomical Journal on Dec. 10, provide support for the existence of a hypothesized Planet Nine, an undiscovered planet with a similar orbit to HD 106906 b, according to UC Berkeley graduate and lead author Meiji Nguyen. The paper also raised questions about how a massive planet such as HD 106906 b is formed.

Though astronomers first discovered HD 106906 b as a planet in 2013, the first images of the planet were taken in 2004, according to Nguyen. Until now, researchers within the field of astronomy were unsure whether the planet was stationary or in orbit.

“There was very little hope by a lot of groups to actually see any meaningful motion,” Nguyen said. “We were trying to figure out, can we measure precisely enough the position of this thing to see if we can get a meaningful type of orbit or motion?”

The team looked at 14 years of images of the planet in hopes that they could detect motion over time, Nguyen added. They used data collected from both the Hubble Space Telescope and the Gaia Space Telescope to pinpoint the location of HD 106906, the binary star that HD 106906 b orbits.

Possible orbits for the planet were then mapped out by the researchers. These orbits support the hypothesis that HD 106906 b causes perturbations in the shape of the debris disk around the star HD 106906, which could explain why the debris disk has an asymmetrical shape, according to Nguyen.

“The immediate next steps will be for theorists to use the orbital information that we provided to nail down the dynamical history of HD 106906 b and how it co-evolved with the dusty disk and inner planetary system closer to the binary star,” said adjunct professor of astronomy and study co-author Paul Kalas in an email.

The findings also support the existence of Planet Nine, which could explain the orbits of objects in the debris disk analog of our solar system, known as the Kuiper Belt, according to Nguyen.

There is a cluster of objects within the Kuiper Belt that have orbitals all going in one direction, Nguyen said. To explain this, researchers proposed that a massive ninth planet exists and is pushing these objects in the opposite direction.

“They haven’t discovered Planet Nine yet,” Nguyen said. “It might not actually exist. One thing that’s interesting is that now that we found evidence of an object on an orbit similar to Planet Nine existing somewhere out in nature, it makes it much more plausible.”

Contact Emma Rooholfada at [email protected] and follow her on Twitter at @erooholfada_dc.