TOKYO: Astronomers have reported evidence of a 2002 XV93 atmosphere around a small Kuiper Belt object previously thought too small to hold gas, according to a study published in Nature Astronomy.
The object, formally known as (612533) 2002 XV93, is a trans-Neptunian object about 500 kilometres wide, far smaller than Pluto’s 2,377-kilometre diameter, the National Astronomical Observatory of Japan said.
A team led by Ko Arimatsu of the NAOJ Ishigakijima Astronomical Observatory detected the signal during a January 10, 2024, stellar occultation, when the object passed in front of a background star as seen from Japan.
SMALL OUTER SOLAR SYSTEM OBJECT SURPRISES SCIENTISTS WITH THIN ATMOSPHERE
Astronomers detected a faint atmosphere around 2002 X-V-93, a small object beyond Neptune in the Kuiper Belt.
The discovery came during a stellar occultation that showed a gradual dimming of starlight.… pic.twitter.com/3erPwpQtDu
— NewsForce (@Newsforce) May 7, 2026The University of Tokyo said observations from multiple locations in Japan showed the star dimmed gradually at the object’s edge, a pattern consistent with starlight passing through a very thin atmosphere.
The Nature Astronomy paper reported a surface pressure of about 100 to 200 nanobars, showing that even a few-hundred-kilometre trans-Neptunian object can host at least a temporary atmosphere.
The finding is unusual because weak gravity and frigid outer solar system conditions usually leave most small icy bodies beyond Neptune airless.
Calculations suggest the atmosphere should disappear in less than 1,000 years unless something replenishes it, meaning NAOJ said it was likely created or renewed recently.
Researchers said possible explanations include gas released from inside the object or material produced by a recent impact, while James Webb Space Telescope data showed no clear surface frozen gases that could easily sustain the atmosphere.
