Scientists have reported the discovery of a “Trans-Neptunian object” whose orbital movements are highly unusual. Researchers suggest this strangely behaving rock could be orbiting a larger planet in deep space, bringing astronomers one step closer to finding Planet Nine.

A team of astronomers representing 35 universities and institutions announced the detection of the mystery rock this week, dubbed 2015 BP519, and have observed its eccentric orbital stability with new insight. The researchers published their dynamical analysis this week and describe the mystery rock within the context of the Planet Nine Hypothesis. The published data suggests that 2015 BP519 “adds to the circumstantial evidence for the existence of this proposed new member of the Solar System.”

The team, led by Juliette Becker of the University of Michigan, discovered 2015 BP519 by using data from the Dark Energy Survey, an ongoing project that seeks to map parts of space beyond what is known. The team had not expected to find orbiting objects in the data, let alone an object that orbits at a different angle than the known eight planets in the Solar System.

Trajectory of 2015 BP519 over its measured four-opposition arc. Red dots along the trajectory indicate points at which it was observed by the Dark Energy Survey
Trajectory of 2015 BP519 over its measured four-opposition arc. Red dots along the trajectory indicate points at which it was observed by the Dark Energy Survey

Whereas the known planets move along the same orbital plane due to the sun’s gravitational pull, Becker’s team says 2015 BP519 is tilted 54 degrees from that plane. This could mean that the object is influenced by a separate gravitational pull, such as a giant “ghost planet” that 2015 BP519 orbits much like a planet’s moon.

Astronomers have been searching for Planet Nine since early 2016, when astronomers Konstantin Batygin and Michael Brown from the California Institute of Technology found a group of distant objects orbiting the sun at an axis different from the known planets. These Kuiper Belt Objects (KBOs) created eccentric orbital patterns, leading Batygin and Brown to suggest they were being pulled by something much larger than Earth and lurking somewhere farther from the sun than Neptune.

Becker’s paper expounds on these concepts and presents new data to support the Planet Nine Hypothesis, but will still need to be peer-reviewed and formally published. While the strange orbital behavior of 2015 BP519 may not confirm the existence of Planet Nine just yet, it offers a glimpse of how little is known about deep space and will serve as an asset to the scientists actively looking for the contested ghost planet.

Photos via Becker et al. DISCOVERY AND DYNAMICAL ANALYSIS OF AN EXTREME TRANS-NEPTUNIAN OBJECT WITH A HIGH ORBITAL INCLINATION, Caltech/R. Hurt (IPAC)