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Study makes case for large planet in outer solar system

An artist's rendition of the proposed planet. CREDIT CALTECH/R.HURT(IPAC)

Using a computer simulation to model the unusual orbits of several distant Kuiper Belt Objects (KBOs), two astronomers say they have found evidence for the presence of a giant planet orbiting 19 billion miles from the Sun.

That distance is roughly the equivalent of 200 astronomical units (AU), with one AU equal to the Earth-Sun distance, or 93 million miles. In contrast, Pluto orbits between 29.7 and 49.3 AU from the Sun.

The claim is the latest of several made over many years regarding the existence of one or more as yet undiscovered planets in the outer solar system.

Caltech astronomers Michael Brown and Konstantin Batygin began the computer simulation upon realizing the long axes of six small Kuiper Belt Objects all point in the same direction and share the same tilt to the ecliptic plane, in which most of the solar system’s planets orbit.

The shared pattern could not be explained solely by any interactions these small objects had with the solar system’s four large gas giants.

Calculations showed that the likelihood of these six objects shared patterns to be 0.007 percent. That is when they started considering the influence of a large planet whose perihelion or closest point to the Sun is directly opposite the perihelion of these objects.

The presence of such a planet could explain not only the unusual orbits of these six strange KBOs but also that of two other remote worlds, the inner Oort Cloud Objects Sedna and 2012 VP113.

Furthermore, if it existed, this large planet would push other KBOs into perpendicular orbits, a phenomenon actually observed in the outer Kuiper Belt over the last three years.

“Although we were initially quite skeptical that this planet could exist, as we continued to investigate its orbit and what it would mean for the outer solar system, we became increasingly convinced that it is out there,” Batygin stated.

The six most distant known objects in the Solar System with orbits exclusively beyond Neptune (magenta) all mysteriously line up in a single direction. Also, when viewed in three dimensions, they tilt nearly identically away from the plane of the Solar System. Batygin and Brown show that a planet with 10 times the mass of the Earth in a distant eccentric orbit anti-aligned with the other six objects (orange) is required to maintain this configuration. Image Credit: Caltech/R. Hurt (IPAC)

The six most distant known objects in the Solar System with orbits exclusively beyond Neptune (magenta) all mysteriously line up in a single direction. Also, when viewed in three dimensions, they tilt nearly identically away from the plane of the Solar System. Batygin and Brown show that a planet with 10 times the mass of the Earth in a distant eccentric orbit anti-aligned with the other six objects (orange) is required to maintain this configuration. Image Credit: Caltech/R. Hurt (IPAC)

Brown and Batygin estimate the unseen planet to have approximately ten times the mass of the Earth and travel in an eccentric orbit, taking between 10,000 and 20,000 years to circle the Sun.

They theorize the planet formed with the other gas giants only to be subsequently thrown into a much more distant orbit through a gravitational interaction with another body.

While the computer model provides a general idea of the planet’s orbit, it cannot pinpoint its exact location.

Finding the planet will be easier if it is near its perihelion, or closest point to the Sun but much more difficult if it is near its aphelion, or furthest point.

The study has been published in the January 20 issue of the Astrophysical Journal.

Laurel Kornfeld

Laurel Kornfeld

Staff Writer
Laurel Kornfeld is a freelance writer and amateur astronomer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science in astronomy from Swinburne University’s Astronomy Online program.
About Laurel Kornfeld (1100 Articles)
Laurel Kornfeld is a freelance writer and amateur astronomer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science in astronomy from Swinburne University’s Astronomy Online program.