CAPE CANAVERAL (Florida) • A previously unknown giant planet may have been discovered lurking in the outer reaches of our solar system, said United States scientists.
Nicknamed "Planet Nine", the object has "a mass about 10 times that of Earth" and follows a "bizarre, highly elongated orbit in the distant solar system", said a statement by researchers at the California Institute of Technology on Wednesday. "In fact, it would take this new planet between 10,000 and 20,000 years to make just one full orbit around the Sun."
So far, the planet has not been observed directly. Rather, astronomers Mike Brown and Konstantin Batygin found it through mathematical modelling and computer simulations.
In a paper published in The Astronomical Journal, Dr Brown andDr Batygin lay out a detailed circumstantial argument for the planet's existence in what astronomers have observed - a half-dozen small bodies in distant elliptical orbits.
The presumed planet has about 5,000 times the mass of Pluto, and scientists believe its gravity has affected the motion of these dwarf planets in the outer solar system, essentially perturbing celestial bodies in the field of icy objects and debris beyond Neptune known as the Kuiper Belt.
THERE'S MORE OUT THERE
It's a pretty substantial chunk of our solar system that's still out there to be found, which is pretty exciting.
DR MIKE BROWN, astronomer
What is striking, the scientists said, is that the orbits of all six loop outwards in the same quadrant of the solar system and are tilted at about the same angle. The odds of that happening by chance are about one in 14,000, Dr Batygin said. A ninth planet could be gravitationally herding them into these orbits.
Pluto, at its most distant, is 7.4 billion km from the Sun. The potential ninth planet, at its closest, would be about 32 billion km away; at its farthest, it could be 160 billion km away.
Dr Brown and his colleagues say Planet Nine could have been cast off during the early formation of the solar system, when four major cores grabbed up the gas around them and formed Jupiter, Saturn, Uranus and Neptune.
Perhaps Planet Nine represented a fifth core, which may have come too close to Jupiter or Saturn and been ejected into its current, distant orbit, said Dr Brown.
A host of powerful telescopes are currently hunting for Planet Nine, including the twin 10m telescopes at the W. M. Keck Observatory and the Subaru Telescope on Maunakea in Hawaii.
"It's a pretty substantial chunk of our solar system that's still out there to be found, which is pretty exciting," said Dr Brown.
"Although we were initially quite sceptical that this planet could exist, as we continued to investigate its orbit and what it would mean for the outer solar system, we've become increasingly convinced that it is out there," said Dr Batygin, an assistant professor of planetary science.
"For the first time in over 150 years, there is solid evidence that the solar system's planetary census is incomplete."
AGENCE FRANCE-PRESSE, NEW YORK TIMES, REUTERS