Spaceflight Insider

KBO could be evidence for a giant planet in the outer solar system

Artist's Concept of a Kuiper Belt Object

Artist’s Concept of a Kuiper Belt Object. Credits: NASA / ESA / A. Schaller (STScI)

The discovery of a distant Kuiper Belt Object (KBO) with an extremely eccentric orbit could be evidence that a giant planet is waiting to be discovered in the outer solar system.

KBO BP519 was discovered by scientists analyzing data collected by the Dark Energy Survey, which observes a region far above the orbital plane of most of the solar system’s planets as part of a project to measure acceleration of the universe’s expansion.

It orbits the Sun at a tilt of some 54 degrees from the plane of the inner solar system planets’ orbits.

Like several other KBOs found in 2016, which all orbit at the same unique angle to the plane of the inner planets, 2015 BP519’s position suggests it is being influenced by the gravitational pull of a much larger object, sometimes referred to as “Planet X” or “Planet Nine,” which may be shepherding it and the other above KBOs into this strange orbit.

Since the 2016 discovery of these KBOs orbiting at the same distinct angle, scientists have been searching for a hypothesized large planet influencing their orbits, which could be either a super-Earth or a gas giant.

One possibility is 2015 BP519, described as “the most extreme Trans-Neptunian Object discovered to date,” is actually a moon of the large planet, which some astronomers estimate to be ten times as massive as the Earth.

According to the researchers’ theory, the giant planet is located approximately 149 billion kilometers from the Sun, or 75 times the distance between the Sun and Pluto.

Computer models estimate that at such a great distance from the Sun, this planet could take between 10,000 and 20,000 years to complete a single solar orbit.

Scientists do not know exactly where the planet might be, and searching for it is challenging because if it exists, its distance makes it dark.

“Finding a ten-Earth-mass planet in our own solar system would be a discovery of unrivaled scientific magnitude,” emphasized Greg Laughlin of Yale University, who was not involved in the study.

Although computer simulations support the notion that these KBOs’ strange orbits are the result of perturbations from a large, unseen planet, some astronomers attribute their orbits to the solar system having had a close encounter with one or more stars in its early years.

Like many stars, the Sun is believed to have initially formed within a star cluster. Over long periods of time, the stars dispersed. The gravitational pull of one or more closely passing stars could also have pushed 2015 BP519 and the other KBOs with strange orbits into their current positions.

In other stellar systems, planets with two to ten Earth masses have proven to be very common, so finding one in our own solar system would be consistent with recent exoplanet discoveries, Laughlin said.

A paper discussing these findings has been published in the Astrophysical Journal.




Laurel Kornfeld is an amateur astronomer and freelance writer 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 from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.

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