Astronomers have spotted something surprising in the far outer Solar System—a faint, short-lived atmosphere clinging to a tiny icy world that shouldn’t be able to hold one at all. The object, called 2002XV93, is far smaller than Pluto, yet observations during a rare stellar alignment revealed its presence through a subtle dimming of starlight. Even more puzzling, calculations suggest this atmosphere should vanish within about 1,000 years unless it’s constantly being replenished.

A group of professional and amateur astronomers in Japan has uncovered evidence that a small, distant object in the outer Solar System is surrounded by a thin atmosphere. The finding is surprising because the object is far too small to hold onto gas for long, raising new questions about how and when this atmosphere formed. Future observations will be needed to better understand its composition and origin.

Far beyond Neptune’s orbit, thousands of icy bodies known as trans-Neptunian objects (TNOs) circle the Sun. Pluto is the most well-known example and is one of the few with a confirmed thin atmosphere. For most TNOs, however, the combination of extremely low temperatures and weak gravity makes it unlikely for them to retain any gases. As a result, scientists generally expect these distant objects to be airless.