Evidence Points to Mysterious 'Planet Y' Lurking in Our Solar System's Outer Regions

The scientific community remains divided on the existence of Planet X, which has yet to be conclusively discovered.

New evidence has emerged suggesting the potential presence of an undiscovered planet in the outer regions of our solar system. According to research published in the Monthly Notices of the Royal Astronomical Society: Letters, scientists are now proposing the existence of "Planet Y," a hypothetical celestial body inferred from unusual orbital patterns observed in distant Kuiper Belt objects.

Astronomers have long been fascinated by the Kuiper Belt, a extensive ring of icy bodies located beyond Neptune, viewing it as a potential hiding place for undiscovered planets. While Planet Y hasn't been directly observed, its existence is suggested by unexpected inclinations in the orbits of approximately 50 remote objects.

Princeton University doctoral candidate Amir Siraj, who led the study, explained, "One explanation is the presence of an unseen planet, probably smaller than the Earth and probably bigger than Mercury, orbiting in the deep outer solar system. This paper is not a discovery of a planet, but it's certainly the discovery of a puzzle for which a planet is a likely solution."

The search for hidden planets beyond Neptune has a rich history dating back to the early 20th century, following Neptune's discovery in 1846. Initially, Pluto was considered a candidate for the theoretical Planet X when discovered in 1930, before being reclassified as a dwarf planet due to its relatively small size.

Planet Y differs from the previously hypothesized Planet Nine, which scientists believe may be five to ten times Earth's mass and orbiting at a much greater distance. Siraj suggested that both hypothetical planets could potentially exist simultaneously within our solar system, stating, "I think it's a very exciting discussion, and actually that was the motivation for us to investigate the issue."

Siraj's research team observed that beyond approximately 80 times the Earth-Sun distance, there exists a tilt of around 15 degrees that cannot be explained by conventional planetary formation models or the influence of passing stars. "It was quite a surprise to find that the solar system suddenly appears to be tilted by about 15 degrees, and this is what sparked the Planet Y hypothesis," Siraj noted.

Computer simulations conducted by Siraj and colleagues revealed that existing models, including those accounting for Planet Nine, failed to explain this observed tilt. They propose that Planet Y likely possesses a mass between that of Mercury and Earth, orbits at 100 to 200 times the Earth-Sun distance, and has an orbital tilt of at least 10 degrees relative to the known planets in our solar system.

Despite these compelling findings, Planet Y's existence remains theoretical. "With these roughly 50 objects, the statistical significance is in the 96% to 98% range," Siraj explained. "It's strong, but it's not definitive yet."

The Vera C. Rubin Observatory, scheduled to begin its decade-long survey in Chile this fall, may provide the definitive evidence needed to confirm Planet Y. Equipped with the world's largest digital camera, this advanced telescope will capture images of the entire sky every three days, potentially offering conclusive insights regarding Planet Y's existence.