Researchers find possible ninth planet beyond Neptune

A Nasa artist's image of the planets in the solar system.
A Nasa artist's image of the planets in the solar system.PHOTO: NASA

CAPE CANAVERAL, FLORIDA (REUTERS/AFP) - The solar system may host a ninth planet that is about 10 times bigger than Earth and orbiting far beyond Neptune, according to research published on Wednesday.

Computer simulations show that the mystery planet, if it exists, would orbit about 20 times farther away from the sun than Earth, said astronomers with the California Institute of Technology (CalTech) in Pasadena.

The object follows a “bizarre, highly elongated orbit in the distant solar system”, said a statement by Caltech researchers.

“In fact, it would take this new planet between 10,000 and 20,000 years to make just one full orbit around the Sun.”

The research is published in this week's Astronomical Journal.

Researchers Konstantin Batygin and Mike Brown say they have not yet observed the object directly.

Rather, they found it through mathematical modelling and computer simulations.

The presumed planet has about 5,000 times the mass of Pluto, and scientists believe its gravity has affected the motion of 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.

“Like a parent maintaining the arc of a child on a swing with periodic pushes, Planet Nine nudges the orbits of distant Kuiper Belt objects such that their configuration with relation to the planet is preserved,” explained CalTech in a statement.

The planet 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, that may have gotten 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.

“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.”