Small, Distant World Found to Hold a Surprising Atmosphere
TOKYO – In a discovery that challenges fundamental assumptions about planetary science, astronomers have detected an atmosphere on a tiny world located nearly 3.5 billion miles from the Sun—close to the orbit of Pluto.
A Tiny World in the Darkness
The celestial body, formally designated 2002 XV93, is remarkably small, measuring just over 300 miles wide. Given its size, its gravitational pull is extremely weak. Under normal circumstances, such a small object would be unable to hold onto an atmosphere for long; any surrounding gas would be expected to have dissipated into the vacuum of space long ago.
Furthermore, the environment at such an extreme distance is brutally cold. Temperatures are so frigid that most molecules which are gaseous on Earth—like oxygen and nitrogen—would freeze solid. Scientists had previously assumed that any residual atmosphere on such an object would inevitably freeze and fall to the surface as frost.
The Discovery
The surprising finding was made by a team of Japanese astronomers led by Ko Arimatsu of the National Astronomical Observatory of Japan. Their results were published in the journal Nature Astronomy.
"We were very surprised," said Arimatsu, expressing the team's reaction to the unexpected presence of an atmosphere on a world where it should not exist.
Implications
The detection suggests that our understanding of how the solar system's smallest and most distant bodies hold onto gas may be incomplete. The presence of an atmosphere on 2002 XV93 opens up new questions about the composition of the world and the processes that allow such a thin layer of gas to persist against the odds.