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Hubble spots distant exoplanet that could be equivalent to Planet Nine

Artist’s Impression of Exoplanet HD 106906b
This 11-Jupiter-mass exoplanet called HD106906 b occupies an unlikely orbit around a double star 336 light-years away and it may be offering clues to something that might be much closer to home: a hypothesized distant member of our Solar System dubbed “Planet Nine.” This is the first time that astronomers have been able to measure the motion of a massive Jupiter-like planet that is orbiting very far away from its host stars and visible debris disc. ESA/Hubble, M. Kornmesser

There’s a theory, hotly debated in astronomical circles, that there could be a ninth planet lurking far out in the depths of our solar system in the space beyond Pluto. This hypothesized “Planet Nine” is thought to exist because of the movements of bodies around it, which suggest there could be an object which we can’t see directly which is having a gravitational effect on other objects nearby. But no one is able to say for sure whether this planet exists or not.

Now, astronomers using the Hubble Space Telescope have found an interesting equivalent to Planet Nine in a distant star system. The planet HD106906 b is eleven times the mass of Jupiter and orbits extremely far away from its twin host stars, located 336 light-years away from Earth. The planet orbits these stars at an incredible 730 times the distance of the Earth to the sun, and a year there lasts more than 15,000 Earth years. This shows that it is possible for planets to orbit very far from their host stars.

Planet HD106906 b is weird in other ways too as it has a very inclined and eccentric orbit, which has scientists interested in how it came to be located where it is. “To highlight why this is weird, we can just look at our own solar system and see that all of the planets lie roughly in the same plane,” explained lead author Meiji Nguyen of the University of California, Berkeley in a statement. “It would be bizarre if, say, Jupiter just happened to be inclined 30 degrees relative to the plane that every other planet orbits in. This raises all sorts of questions about how HD 106906 b ended up so far out on such an inclined orbit.”

The researchers think the planet might have started closer to its star and been pushed out to a more distant orbit over time by the disk of gas in the system. Then a passing star might have nudged the planet into a stable orbit. This could be an explanation for how a distant Planet Nine could have been pushed out beyond Pluto in our own solar system.

“It’s as if we have a time machine for our own solar system going back 4.6 billion years to see what may have happened when our young solar system was dynamically active and everything was being jostled around and rearranged,” explained team member Paul Kalas of the University of California, Berkeley.

The researchers intend to keep studying this unusual planet and hope to learn more about how it formed and what processes pushed it into its unusual orbit.

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