DATE2026.05.05 #Press Releases

First non-Pluto object to discover an atmosphere in the outer solar system

Disclaimer: machine translated by DeepL which may contain errors.

Capturing the gradual dimming caused by the atmosphere on video

Summary

A collaborative research team of amateur observers and professional astronomers led by researchers from the National Astronomical Observatory of Japan (Ishigakijima Astronomical Observatory), The University of Tokyo, and the University of Occupational and Environmental Health, Japan has observed a phenomenon called occultation, in which an trans-Neptunian object (612533) 2002 XV₉₃ passes in front of a background star on January 10, 2024. The observations were carried out at three locations in Japan (Kyoto city; Kiso Observatory; and Tamura-gun, Fukushima). The data obtained by Tomo-e Gozen at Kiso Observatory revealed an unexpectedly gradual change in the starlight at the edge of the object, and a detailed analysis revealed the existence of a very thin atmosphere around 2002 XV₉₃. This achievement is the first indication of the existence of an atmosphere in a trans-Neptunian object object other than Pluto. Furthermore, 2002 XV93 is the first solar-system object,  excluding planets, quasi-planets, and large satellites, to clearly show the existence of an atmosphere, making it the farthest object in the solar system for which an atmosphere has been observed. This discovery, which shows that even relatively small objects with a diameter of about 500 kilometers can have an atmosphere, at least temporarily, is an achievement that revises the conventional understanding of atmosphere formation and volatile matter retention in solar-system bodies and the activity of trans-Neptunian objects
The findings were published in the British scientific journal Nature Astronomy on May 5, 2026 (JST).

An artist's concept of the trans-Neptunian object (612533) 2002 XV₉₃, for which an atmosphere was discovered in this study.
Credit: Kiso Observatory, The University of Tokyo

Links

National Astronomical Observatory of Japan, National Institutes of Natural Sciences

Kiso Observatory, The University of Tokyo

Journals