Astronomers detect atmosphere on tiny icy world beyond Pluto

Astronomers have detected a thin atmosphere around a small, icy celestial body in the outer solar system, marking the second known object beyond Neptune with such a feature after Pluto. The object, designated (612533) 2002 XV93, is roughly 310 miles (500 kilometers) in diameter and orbits the sun at a distance similar to Pluto. Researchers observed the atmosphere using telescopes in Japan as the object passed in front of a background star in January 2024, causing a brief dimming of starlight. The atmosphere is estimated to be 5 million to 10 million times thinner than Earth's and 50 to 100 times thinner than Pluto's. Scientists suggest it may be composed of methane, nitrogen, or carbon monoxide. The discovery, published in the journal Nature Astronomy, challenges the conventional view that atmospheres are limited to large planets, dwarf planets, and some moons. Lead researcher Ko Arimatsu of the National Astronomical Observatory of Japan emphasized the need for independent verification of the findings. Alan Stern, lead scientist of NASA's New Horizons mission, called the discovery "amazing" but noted its implications would be profound if confirmed. The object, classified as a plutino, completes two orbits around the sun for every three orbits of Neptune. Its atmosphere's origin remains uncertain, with possible explanations including volcanic activity or a comet impact.