Traci Watson

Special for USA TODAY

The image of our solar system may soon undergo a radical makeover.

Scientists revealed evidence Wednesday of a bizarre new planet five to 10 times more massive than the Earth and at least 200 times farther from the sun. If the new planet is confirmed, it would raise the solar system’s planet tally from eight to nine. It would also verify the presence of a world in the coldest, most remote reaches of the solar system — a world unlike any of the known planets.

“This is the first serious claim for the existence of an additional planet in the solar system,” said planetary scientist Alessandro Morbidelli of France’s Observatory of the Cote d’Azur, who was not involved with the new study. If true, “it would change the portrait of the solar system for everyone.”

Other researchers say the existence of so-called “Planet Nine,” while plausible, still needs to be confirmed. But experts also say the study laying out the case contains the most convincing evidence yet that a giant planet hovers much farther away than ever imagined.

“We tried hard ourselves to prove that we were wrong,” said study co-author Mike Brown of Caltech. “We couldn’t do it, but I hope people are sharpening their pencils right now.”

If Planet Nine is the real deal, it would be one of the most delicious ironies in recent scientific history. Until now, Brown has been best known as the man who killed Pluto. Brown’s discovery a decade ago of an icy body called Eris – roughly the size of Pluto but much farther from the sun – helped goad astronomers into a humiliating demotion of Pluto from planet to “dwarf planet,” a decision that shrank the solar system from nine planets to eight.

"OK, OK, I am now willing to admit: I DO believe that the solar system has nine planets," Brown tweeted Wednesday from his aptly named account — @plutokiller.

Brown and his Caltech colleague Konstantin Batygin base their argument of Planet Nine's existence on an analysis of a handful of distant worlds orbiting the sun far beyond the orbit of Neptune, the farthest true planet. Six of these small objects have orbits that are, against the odds, all aligned at one end. Their paths are also tilted in the same way compared to the eight bona-fide planets.

To Brown and Batygin, that suggested some large object is secretly exerting its powers over the outer solar system. Further analysis of other small worlds beyond Neptune showed they, too, seemed to be under the influence of a massive planet, the scientists reported in The Astronomical Journal.

Those conclusions may yet unravel, but “right now the best explanation is a giant planet,” said astronomer Scott Sheppard of the Carnegie Institution in Washington D.C., whose research helped put Brown and Batygin on the scent of Planet Nine. “It’s still early stages … but it’s a very strong possibility that this planet exists out there.”

New Pluto images reignite debate over dwarf planet status

In search of irrefutable proof, Brown and Batygin are now searching for Planet Nine with two different telescopes. This hypothesized world is probably very far from Earth at the moment – it needs 10,000 to 20,000 years to make one circuit around the sun – and therefore difficult to see, Brown said. But he thinks Planet Nine is within reach of the world’s most powerful telescopes.

If Planet Nine really exists, it could help scientists understand the birth of the solar system, said Scott Kenyon of the Harvard-Smithsonian Center for Astrophysics.

"It's a challenge" to understand how a planet would've gotten way out there and survived, he said, so Planet Nine will help researchers winnow their ideas for "the early history of our planetary system."

It's existence would also help make our own solar system a little less weird. None of the planets in our solar system resemble the most common types of planets outside it. But Planet Nine does.

“We are becoming more normal by finding this very strange planet out there,” Brown said. “Just with this one extra planet, the solar system is much more like other planetary systems we’ve been finding in the galaxy.”