A teeny-tiny world beyond Pluto appears to have an atmosphere

An icy world, perhaps just 300 miles wide and far beyond Pluto, may have air, challenging the assumption that small space objects can't hold onto an atmosphere.

This world, known as 2002 XV93, orbits in a distant region sprinkled with leftover rubble from our solar system's early planet-building days. Astronomers often study this ancient detritus, referred to as Trans-Neptunian Objects, by waiting for remnants to pass in front of stars. During rare alignments, researchers can measure how...