Japanese astronomers led by Ko Arimatsu recorded an occultation on Jan. 10, 2024, when the object 2002 XV93 passed in front of a star. Telescopes in Kyoto and Kiso measured a 16‑second dip that faded and brightened gradually, a refraction signature of a thin gas layer. The result, published in Nature Astronomy, defies expectations for a body 300 miles across and 3.5 billion miles from the Sun.

The starlight dimmed for about 1.5 seconds before vanishing, then recovered at the same rate, indicating refraction by an atmosphere estimated at one to two 10‑millionths of Earth’s pressure. Such a tenuous envelope is unexpected for a 300‑mile world whose weak gravity should let gases escape and whose frigid environment should freeze them onto the surface.

Only Makemake has shown a comparable methane veil, while larger TNOs such as Eris and Pluto exhibit well‑documented atmospheres. Arimatsu’s team suggests cryovolcanic outgassing or a recent impact could supply the fleeting gases, ruling out a stable ring as less plausible. The discovery adds a new variable for models of outer‑solar‑system evolution and may steer future telescope proposals toward more occultation campaigns.