Astronomers Detect Atmosphere on Distant Trans-Neptunian Object
A thin atmosphere has been discovered around (612533) 2002 XV93, a small trans-Neptunian object, challenging previous assumptions about such bodies.
Astronomers have identified a thin atmosphere surrounding (612533) 2002 XV93, a trans-Neptunian object approximately 500 kilometers in diameter, located beyond Neptune in the Kuiper Belt. This discovery challenges the prevailing belief that such small, distant bodies lack the gravity to retain atmospheres.
The atmosphere was detected during a stellar occultation on January 10, 2024, when 2002 XV93 passed in front of a distant star. Observers noted a gradual dimming of the star's light, indicative of an atmospheric layer. The surface pressure of this atmosphere is estimated to be between 100 and 200 nanobars, making it 5 to 10 million times thinner than Earth's atmosphere and 50 to 100 times thinner than Pluto's.
The composition of the atmosphere is uncertain, but it may contain methane, nitrogen, or carbon monoxide. Notably, previous observations by the James Webb Space Telescope did not detect these ices on 2002 XV93's surface, suggesting the atmosphere might originate from internal processes or recent external events.
Two primary hypotheses have been proposed: a recent cometary impact that released gases, or cryovolcanic activity bringing subsurface volatiles to the surface. Given the rapid rate at which such a thin atmosphere would dissipate, its current presence implies a recent formation or replenishment.
"This discovery suggests that the traditional idea that global dense atmospheres form only around larger planets must be revised," said Ko Arimatsu of the National Astronomical Observatory of Japan.
Further observations, particularly with the James Webb Space Telescope, are planned to determine the atmosphere's composition and monitor its density over time. A decrease in density would support the impact hypothesis, while a stable or varying density might indicate ongoing internal outgassing.
This finding not only challenges existing models of atmospheric retention on small celestial bodies but also opens new avenues for understanding the dynamic processes at play in the outer solar system.