Astronomers in Japan have detected signs of an atmosphere around a small, icy body orbiting beyond Pluto — a finding scientists previously considered impossible for objects so far from the Sun. The discovery, announced on May 4, 2026, challenges long-held assumptions about atmospheric retention in the outer solar system.
A Tiny World with a Thin Veil
The object, designated (612533) 2002 XV93, is roughly 500 kilometers in diameter — significantly smaller than both Pluto (2,370 km) and Eris (2,326 km), the two largest known trans-Neptunian objects. Located about 40 times farther from the Sun than Earth — roughly 6 billion kilometers away — it takes 247 years to complete one orbit. Scientists believe it formed during the early days of our solar system, over 4.5 billion years ago.
Like many distant, faint objects, it was observed only when its orbit carried it directly in front of a distant star — an event known as a stellar occultation. During such a passage in January 2024, Japanese astronomers — aided by an amateur observer — noticed that the star’s light did not reappear immediately after being blocked. This delay suggests a thin atmospheric layer refracted and filtered part of the starlight.
A Thin, Cold Atmosphere
According to findings published in the journal Nature Astronomy, the atmosphere of (612533) 2002 XV93 is estimated to be five to ten million times thinner than Earth’s. Methane, nitrogen, and carbon monoxide are likely the dominant gases.
“Until now, Pluto was the only trans-Neptunian object confirmed to host an atmosphere,” explained Ko Arimatsu, lead author of the study and researcher at the National Astronomical Observatory of Japan, in an interview with Agence France-Presse. “This discovery challenges the widely accepted idea that small, icy worlds in the outer solar system are, for the most part, airless.”
Implications for Planetary Classification
If confirmed, this would make (612533) 2002 XV93 only the second known object beyond Neptune with a detectable atmosphere — after Pluto. That fact carries broader implications: some advocates have recently pushed to reclassify Pluto as a planet again, citing its complex geology and atmosphere as distinguishing features. However, finding another similarly sized, atmosphere-bearing object in the same region weakens one key argument for such a reclassification — namely, that Pluto is uniquely complex among its peers.