Planet Nine Evidence Grows After Scientists Find Distant Object with Extraordinary Orbit

Two years ago, scientists from the California Institute of Technology (Caltech) found evidence to suggest that a planet larger than Earth could be hiding beyond the orbit of Pluto, out in the furthest reaches of the Solar System.

The researchers didn’t directly observe the hypothetical ninth planet, but they did predict its existence based on the strange orbits of a handful of distant, icy worlds in the Kuiper belt—a disc of primarily small and rocky bodies which begins just past the orbit of Neptune—which were extremely unlikely to have occurred by chance.

Since this discovery, scientists around the world have been trying to uncover more evidence of Planet Nine. Now, an international team of researchers has reported the discovery of another distant world, possibly a dwarf planet, which has a bizarre orbit that it is likely being influenced by the ninth planet, they say.

“It’s not proof that Planet Nine exists,” David Gerdes, from the University of Michigan and a co-author of the new paper, told Quanta Magazine. “But I would say the presence of an object like this in our solar system bolsters the case for Planet Nine.”

In a new paper, published on the online pre-print server arXiv.org, the team describe how they uncovered the object in 2014 using data from the Dark Energy Survey—an international, collaborative effort designed to map a vast region of the skies in order to reveal the nature of the mysterious force that is accelerating the expansion of the universe.

The object, known as 2015 BP519, has an extraordinary orbit that’s tilted 54 degrees in relation to the plane of most objects that orbit the Sun. After discovering it, the team tried to investigate 2015 BP519’s origins using computer simulations of the Solar System. However, these tests were not able to adequately explain how the object had ended with such an orbit.

But when they added a ninth planet with properties exactly matching those predicted by the Caltech scientists in 2016, the orbit of 2015 BP519 suddenly made sense.

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“The second you put Planet Nine in the simulations, not only can you form objects like this object, but you absolutely do,” Juliette Becker, a Michigan graduate student and lead author of the study told Quanta.

383_planet_9_art_1_1400 This is an illustration of the hypothetical Planet Nine with its back towards the sun. The object is thought to be gaseous, similar to Uranus and Neptune. Hypothetical lightning lights up the night side. Caltech/R. Hurt (IPAC)

Some researchers, however, caution that Planet Nine may not be the only explanation for 2015 BP519’s strange orbit.

Michele Bannister, a planetary astronomer from Queen’s University Belfast, who was not involved in the study, told Newsweek that while the latest findings were “a great discovery”, other scenarios could account for its tilt.

“This object is unusual because it’s on a high inclination,” she said. “This can be used to maybe tell us some things about its formation process. There are a number of models that suggest you can probably put objects like this into the shape of orbit and the tilt of orbit that we see today.”

One way you can do this, according to Bannister, is to take into account the fact that the early Solar System probably contained 10,000 dwarf planets, in comparison to the 20 or so known examples that currently exist—including Pluto. The gravitational influence of these thousands of dwarf planets may have been sufficient to move 2015 BP519 into its orbit, for example. Nevertheless, Bannister does not rule out the conclusions drawn by the new study.

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