Can a tiny icy world beyond Pluto really have an atmosphere? A new discovery suggests that it can. In a paper published on May 5, 2026, astronomers reported the first detection of an atmosphere around a trans-Neptunian object other than Pluto. The object is called (612533) 2002 XV93. It is only about 500 kilometers wide, much smaller than Pluto, and during the observation it was slightly farther from the Sun than Pluto. That is why the result is so surprising: scientists had long thought that such small, cold bodies could not keep gas around them for very long. (nao.ac.jp)
The discovery came from a clever method called a stellar occultation. On January 10, 2024, 2002 XV93 passed in front of a distant star, as seen from Japan. If the object had no atmosphere, the starlight should have disappeared almost instantly. Instead, observers at multiple sites saw the light fade and return more gently. In one set of data, the change lasted about 1.5 seconds. After detailed analysis, the team concluded that a very thin atmosphere best explained the pattern. They estimated a surface pressure of about 100 to 200 nanobars—around one hundredth of Pluto’s atmospheric pressure. (nao.ac.jp)
This finding is exciting because it changes the old picture of the outer Solar System as a quiet, frozen place. The researchers say the atmosphere on 2002 XV93 should disappear in less than 1,000 years unless new gas is added. That means the atmosphere may have formed recently, or it is still being supplied. Two main ideas are being discussed: gas may be coming from inside the object through icy volcanic activity, or a relatively recent impact may have released gas into space. NAOJ also says observations by the James Webb Space Telescope have not found clear signs of frozen gases on the surface, so the mystery is still open. Future observations will show whether this strange little world is a rare exception—or the first clue that more distant objects can also “breathe.” (nao.ac.jp)
