New evidence points to giant ninth planet on solar system’s edge

The solar system may have a ninth planet after all.

This one is 5,000 times bigger than outcast Pluto and billions of miles farther away, say two scientists who presented "good evidence" for a long-hypothesized Planet X on Wednesday.

The gas giant is thought to be almost as big as its nearest planetary neighbor, Neptune, quite possibly with rings and moons. It's so distant that it would take a mind-blowing 10,000 to 20,000 years to circle the sun.

Planet 9, as the two California Institute of Technology researchers, Konstantin Batygin and Mike Brown, call it, hasn't been spotted yet. They base their prediction on mathematical and computer modeling and anticipate its discovery via telescope within five years.

They reported their research Wednesday in The Astronomical Journal because they want people to help them look for it.

"We could have stayed quiet and quietly spent the next five years searching the skies ourselves and hoping to find it. But I would rather somebody find it sooner than me find it later," Brown told The Associated Press. "I want to see it. I want to see what it looks like. I want to understand where it is, and I think this will help."

Brown, an astronomer, and Batygin, a planetary scientist, feel certain about their prediction, which at first seemed unbelievable to even them.

"For the first time in more than 150 years, there's good evidence that the planetary census of the solar system is incomplete," Batygin said, referring to Neptune's discovery as the eighth planet.

If Planet 9 is detected, Brown insists, there will be no Pluto-style debate about whether it's a true planet. He and Batygin believe it is big — 10 times as massive as Earth — and unlike Pluto, dominates its cosmic neighborhood. Pluto is a gravitational slave to Neptune, they pointed out.

Brown ought to know; he's called the Pluto killer for helping lead the charge against Pluto's planetary status in 2006. (Pluto, once the ninth planet, is now officially considered a dwarf planet.)

"This is what we mean when we say the word 'planet,'" he said.

Another scientist, Alan Stern, said he's withholding judgment on the planet prediction. He is the principal scientist for NASA's New Horizons spacecraft, which buzzed past Pluto last summer in the first-ever visit from Earth. He still sees Pluto as a real planet, not a second-class dwarf.

"This kind of thing comes around every few years. To date, none of those predicts have been borne out by discoveries," he said in an email Wednesday. "I'd be very happy if the Brown-Batygin were the exception to the rule, but we'll have to wait and see. Prediction is not discovery."

Brown and Batygin shaped their calculation on the fact that six objects in the icy Kuiper Belt, a zone at the far reaches of the solar system, appear to have orbits influenced by only one thing: a real planet. The vast, mysterious Kuiper Belt is home to Pluto as well. Brown discovered one of those six objects — Sedna, a large minor planet — more than a decade ago.

"What we have found is a gravitational signature of Planet 9 lurking in the outskirts of the solar system,' Batygin said. Its discovery, he said, would be "era defining."

"We have felt a great disturbance in the force," Brown said.

Scott Sheppard of the Carnegie Institution for Science in Washington said Brown and Batygin's effort takes his own findings to "the next level." Two years ago, he and a colleague suggested a possible giant planet.

"I find this new work very exciting," Sheppard said in an email. "It makes the distant super-Earth planet in our solar system much more real. I would say the odds just went from 50 percent to 75 percent that this distant massive planet is real."

The Associated Press