Astronomers have confirmed, for the first time, a trans-Neptunian object with a thin atmosphere—something previously thought exclusive to Pluto among similar objects. Trans-Neptunian objects (TNOs) are small icy bodies orbiting the Sun beyond Neptune. In a Nature Astronomy paper published today, researchers led by Ko Arimatsu of the National Astronomical Observatory of Japan describe (612533) 2002 XV93, a TNO with a very thin atmosphere. Arimatsu explained that trans-Neptunian objects are so cold and distant that scientists have long assumed they’re largely unchanging and inactive, which made Pluto stand out among them. “Our result shows that even a much smaller object, only about 500 kilometers (311 miles) across, can have an atmosphere, at least temporarily,” Arimatsu told Gizmodo.…