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A possible 'Planet Nine' in the solar system

US scientists say they have evidence of a ninth planet lurking in the outskirts of the solar system. The researchers have only calculated its existence theoretically and physical proof is still needed.

Researchers Konstantin Batygin and Mike Brown of the California Institute of Technology (Caltech) said they calculated the planet's presence through mathematical modeling and computer simulation.

A 'true' planet

"The object, which the researchers have nicknamed Planet Nine, has a mass about 10 times that of the earth and orbits about 20 times farther from the sun on average than does Neptune (which orbits the sun at an average of 2.8 billion miles). In fact, it would take this new planet between 10,000 and 20,000 years to make just one full orbit around the sun," Caltech said on its

website.

Mike Brown said only two true planets had been discovered since ancient times and this would be the third. "It's a pretty substantial chunk of our solar system that's still out there to be found," he added.

The quest for Planet Nine

Batygin and Brown revealed their findings in the latest issue of the

"Astronomical Journal"

and showed how Planet Nine helped explain mysterious features of the Kuiper belt- icy objects and debris beyond Neptune. Planet Nine's existence could also mean that the early solar system was made of five planetary cores instead of four.

"Nature" correspondent Alexandra Witze tweeted this explanatory diagram:

"Scientists have long believed that the early solar system began with four planetary cores that went on to grab all of the gas around them, forming the four gas planets - Jupiter, Saturn, Uranus and Neptune," Caltech's website explained. But for astronomer Mike Brown, "Planet Nine could represent that fifth core, and if it got too close to Jupiter or Saturn, it could have been ejected into its distant eccentric orbit."

Batygin and Brown were now refining their simulations, while Brown and his other colleagues would scout the skies for Planet Nine. If the planet were in the farthest part of its orbit, the world's largest telescopes - at the W.M. Keck Observatory and the Subaru Telescope in Mauna Kea in Hawaii would be needed to find it. If Planet Nine were anywhere in between, many telescopes could spot it, Brown said.

All's well with the solar system

For Batygin, one of the most exciting things about the finding was that Planet Nine "has been the most common type of planet out there." Its existence in the solar system makes us more "normal" in the universe, he said.

Astronomer Mike Brown, best known for demoting Pluto from a planet to the status of a dwarf planet said Planet Nine was an opportunity to rejoice again. Brown - who aptly calls himself "Pluto Killer" on Twitter - posted this message:

"All those people who are mad that Pluto is no longer a planet can be thrilled to know that there is a real planet out there still to be found…Now we can go and find this planet and make the solar system have nine planets once again," he said.

mg/kms (AFP, Reuters, AP)

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