Astronomers' hunt for elusive "Planet Nine" takes surprising twist

Published: Thursday, May 29, 2025 at 3:11 pm

Astronomers Hunting for Planet Nine Discover New Dwarf Planet, Challenging Existing Theories

The search for the elusive "Planet Nine," a hypothetical giant planet at the edge of our solar system, has taken an unexpected turn. Instead of finding the long-sought planet, a team of U.S.-based researchers has discovered a new dwarf planet, named 2017 OF201. This discovery could potentially challenge the Planet Nine theory, which posits that the clustered orbits of icy objects beyond Neptune are influenced by a massive, unseen planet.

The newly discovered dwarf planet, roughly 430 miles across (three times smaller than Pluto), boasts an extremely elongated orbit, taking it far into the Oort cloud, a ring of icy rocks surrounding our solar system. Its orbit, which takes approximately 25,000 years to complete, means it's only observable from Earth for a tiny fraction of that time.

The discovery, considered "lucky" by lead researcher Sihao Cheng, suggests the existence of many similar objects in the Kuiper Belt. The team is now seeking time on the James Webb, Hubble, and ALMA telescopes to further study the dwarf planet. Interestingly, amateur astronomer Sam Deen has already tracked the object using existing datasets, calling it "one of the most interesting discoveries in the outer solar system in the last decade."

The Planet Nine theory arose from the observation of clustered orbits among icy objects in the Kuiper Belt. However, the orbit of 2017 OF201 doesn't align with this trend, potentially weakening the argument for Planet Nine's existence. The Vera Rubin Observatory, set to go online this year, is expected to provide further insights into this mystery. The discovery also highlights the power of open science, as the data used was publicly available, allowing anyone with the right tools to potentially make such a groundbreaking discovery. The discovery was officially announced by the International Astronomical Union's Minor Planet Center on May 21.

Keywords: Planet Nine, dwarf planet, 2017 OF201, Kuiper Belt, Oort cloud, solar system, astronomy, orbit, Neptune, James Webb Telescope, Hubble Telescope, ALMA Telescope, Vera Rubin Observatory, icy rocks, outer solar system, discovery, science, research

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