In the Outer Dark, the Monster Planet Lurks

Pardon my language, but holy heck! “Intriguingly, the astronomers said that details of the orbits hint at perhaps an unseen planet several times the size of Earth at the solar system’s distant outskirts.”

Others suggest that a rogue planet, ejected from the inner solar system, dragged out the Sednoids as it flew through the Kuiper Belt. Dr. Trujillo and Dr. Sheppard point out that Sedna and 2012 VP113 have similar values for one orbital parameter known as the argument of perhelion, as do several other bodies at the edge of the Kuiper Belt. That could be a sign of the gravitational influence of an unseen planet.

Computer simulations showed that the data could be explained by a planet with a mass five times that of Earth at a distance of 23 billion miles from the sun, too dim to show up in current sky surveys.

Harold F. Levison, a theorist at the Southwest Research Institute in Boulder, Colo., who models the begining of the solar system, agreed that was a possibility. “I think they’ve convinced me there’s something going on,” he said of Dr. Trujillo and Dr. Sheppard. “But I think it’s too early to say that it’s a planet.”

If there is a planet, that could reopen the debate over the definition of “planet.” Something that far from the sun would be unlikely to have “cleared the neighborhood around its orbit,” as required by the International Astronomical Union’s current definition. That could lead to a confounding situation in which something larger than Earth would be classified a “dwarf planet” like Pluto.

My first thought, considering the mass, was gas giant. But according to New Scientist it’s likely to be “a giant, unseen rocky world, 10 times the mass of Earth”:

…WISE was looking for the tell-tale warmth of gas giants – a rocky “super-Earth”, like the one Sheppard’s team suggest, would be too cold for the telescope to pick up. “This is too faint for WISE,” says Ned Wright, the space telescope’s principal investigator. Even if the planet has a small internal heat source – and absorbs some sunlight, it would still not generate enough heat to register, he adds.

Not sure about the discrepancy between 5x and 10x Earth, because basically I’m a little too freaked out for a close comparison of the articles.



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