Science: A New Dwarf Planet on the Edge of the Solar System

While astronomers continue to search for the mysterious "ninth planet”, a possible giant hidden in the extremities of the Solar System, another discovery has sparked the interest of the scientific community: 2017 OF201, a celestial body that could soon be added to the dwarf planet category.

• What is 2017 OF201?

The object, with a diameter of approximately 700 km, is three times smaller than Pluto, but large enough to qualify as a dwarf planet, according to the International Astronomical Union's classifications. The discovery was made by a group of American researchers, led by Sihao Cheng (Institute for Advanced Study, New Jersey). Its orbit is extremely elongated, taking it as far as 1,600 astronomical units (AU) from the Sun - that is, 1,600 times the distance between Earth and the Sun, near the Oort Cloud. A complete orbital cycle takes about 25,000 years, and the object is visible from Earth for only 0.5% of that time.

• Impact on the "Planet Nine" theory

For two decades, researchers have speculated about the existence of a ninth planet, much more massive than Earth, that would explain why the orbits of Kuiper Belt objects are aligned in a common direction. But orbital modeling of 2017 OF201 shows that it does not follow this trend - a clue that weakens the case for Planet Nine, according to experts such as Samantha Lawler of the University of Regina, Canada.

"This fantastic discovery calls into question the basic premises of the hypothesis," Cheng says. "More data and precise observations are needed."

• A future of discoveries in the Solar System

A California amateur astronomer, Sam Deen, only 23 years old, helped identify this object, finding it in older databases. He considers it "one of the most exciting discoveries of the last decade." Currently, researchers hope to get observing time using: the James Webb Space Telescope, the Hubble Telescope, the ALMA radio telescope array in Chile, but especially, all eyes are on the Vera C. Rubin Observatory, which is scheduled to become operational in Chile this year. It promises to revolutionize the study of the outer Solar System by continuously and detailed observations of the sky.

• Dwarf planets

After its discovery in 1930, Pluto briefly held the title of the ninth planet in the Solar System. After Pluto's demotion in 2006, the Solar System officially includes five dwarf planets: Pluto, Ceres, Eris, Makemake, Haumea. If confirmed, 2017 OF201 could become the sixth, offering new insights into the formation and diversity of trans-Neptunian objects. The discovery of 2017 OF201 represents a new step in understanding the vast and still mysterious outer Solar System. Far from ending the search for "Planet Nine," it opens up new avenues of research and reinforces the idea that we still know very little about our "cosmic backyard." "I don't think we'll have to wonder about Planet Nine for much longer," says optimist Sam Deen.