Astronomers Detect Atmosphere on Distant Kuiper Belt Object

Astronomers have detected a tenuous atmosphere surrounding (612533) 2002 XV93, a trans-Neptunian object approximately 500 kilometers in diameter, located beyond Pluto in the Kuiper Belt. This discovery marks the first time an atmosphere has been observed on such a small celestial body in this distant region of the solar system.

The research team, led by Ko Arimatsu of Japan's National Astronomical Observatory, observed the object in January 2024 as it passed in front of a background star, causing a brief dimming of the starlight. This event, known as a stellar occultation, provided evidence of an atmospheric layer. Arimatsu noted that finding an atmosphere around such a small object was "genuinely surprising" and challenges "the conventional view that atmospheres are limited to large planets, dwarf planets, and some large moons."

The atmosphere is estimated to be 5 million to 10 million times thinner than Earth's and 50 to 100 times thinner than Pluto's. It likely consists of methane, nitrogen, or carbon monoxide. Potential sources for this atmosphere include recent volcanic activity or a comet impact. Further observations, particularly by NASA's Webb Space Telescope, are needed to confirm the atmosphere's composition and origin. Arimatsu emphasized the importance of future monitoring, stating that if the atmosphere fades over the next several years, it would support an impact origin, while persistence or seasonal variation would suggest ongoing internal gas release.

This finding offers new insights into the dynamic nature of small, icy bodies in the outer solar system and suggests that atmospheres may not be exclusive to larger celestial objects.