If Pluto’s demotion left a world-size hole in your heart, prepare to fill it: Two astronomers at the California Institute of Technology have established pretty good data indicating the existence of a replacement ninth planet. It bears a striking resemblance to Hoth in that it’s enormous, barren, and covered in ice (although no Tauntauns have been spotted) and lurks in an extreme elliptical orbit just on the edge of our solar system, roughly 20 billion miles from Earth. Researchers Konstantin Batygin and Michael E. Brown, who published their findings in The Astronomical Journal this morning, haven’t actually seen the planet, but (somewhat like the discoverers of Neptune and Pluto) they can infer it’s out there by the pull it exerts on other objects in the solar system.
“When we looked at the outer solar system, we realized the most distant objects all swing out in one direction,” Brown explained. “And we realized the only way we could get them to all swing in one direction is if there’s a massive planet, also very distant in the solar system, keeping them in place.” Brown and Batygin at first reacted skeptically that they’d discovered a planet, but over time it became clear the existence of a ninth planet was the only logical explanation for such singular orbits. Occam’s razor strikes again.
If the planet does exist, it’s huge; Brown and Batygin’s calculations put it at ten times the mass of Earth, or 4,500 times the mass of Pluto. It’s also slow; it would take 10,000 to 20,000 years for it to complete a single orbit around the sun. Although Brown told the Times they have “pretty good constraints” on the planet’s orbit, they don’t know exactly where it is in that orbit, which could make it difficult to spot. Brown believes that until someone sees a dot through a telescope, its existence will remain unconfirmed. “Until there’s a direct detection, it’s a hypothesis — even a potentially very good hypothesis,” he told Science.
Incidentally, this is the second time Brown has reshaped our map of the solar system. He was one of the scientists who fought to change Pluto’s designation from planet to dwarf planet, and he even published a book about it. Apparently his daughter has never forgiven him. “She’s still kind of mad about Pluto being demoted,” he told the Washington Post. “She suggested a few years ago that she’d forgive me if I found a new planet. So I guess I’ve been working on this for her.”