Two US astronomers at a California university announced Wednesday they have found evidence of a ninth planet in the solar system.
Nicknamed Planet Nine, the object orbits the sun in a highly elongated path about 20 times farther away from the sun on average than Neptune - the planet farthest from the sun.
The two astronomers, Konstantin Batygin and Mike Brown, said the evidence of Planet Nine's existence comes from mathematical modeling and computer simulations. But they have not seen it.
"This would be a real ninth planet," said Brown in a news release issued by the California Institute of Technology.
It would make up for the loss of Pluto as the ninth planet of the solar system. For decades it held that status, but in 2006 it was downgraded to a dwarf planet.
The putative ninth planet is about 10 times the mass of Earth and 5,000 times the mass of Pluto, making it sufficiently large enough to avoid any debate over whether it is a true planet.
"There have only been two true planets discovered since ancient times, and this would be a third," Brown said. "It's a pretty substantial chunk of our solar system that's still out there to be found, which is pretty exciting."
Alessandro Morbidelli of the Cote d’Azur Observatory in France, said he was convinced of Planet Nine's existence.
"I think the chase is now on to find this planet," he told the New York Times.
If Brown is correct about the existence of Planet Nine, it would not be the first time he played a role in altering the map of the solar system. He discovered a Pluto-size object in 2005 in the Kuiper belt, the ring of icy debris beyond Neptune. That started a discussion over Pluto's classification as a planet and the next year, the International Astronomical Union redefined Pluto as a dwarf planet.