Astronomers Detect Unexpected Atmosphere on Distant Kuiper Belt Object

Japanese astronomers have discovered a thin atmosphere surrounding (612533) 2002 XV93, a trans-Neptunian object approximately 500 kilometers in diameter, located beyond Pluto in the Kuiper Belt. This finding challenges the prevailing belief that such small, icy bodies cannot sustain atmospheres due to their low gravity and frigid temperatures.

The discovery was made during a stellar occultation event in January 2024, when 2002 XV93 passed in front of a distant star. Observations from multiple sites in Japan revealed a gradual dimming of the star's light, indicative of an atmosphere. Lead researcher Ko Arimatsu of the National Astronomical Observatory of Japan stated, "The obtained data are consistent with attenuation by an atmosphere."

Calculations suggest that the atmosphere is extremely tenuous, with a surface pressure between 100 and 200 nanobars—approximately 5 million to 10 million times thinner than Earth's atmosphere. Such an atmosphere is expected to dissipate within 1,000 years unless replenished. The absence of frozen gases on the object's surface, as indicated by James Webb Space Telescope observations, suggests that the atmosphere may result from internal processes like cryovolcanism or recent impacts.

Alan Stern, principal investigator for NASA's New Horizons mission, commented on the significance of the finding, stating, "This is an amazing development, but it sorely needs independent verification. The implications are profound if verified."

Further observations, particularly using the James Webb Space Telescope, are planned to confirm the presence of the atmosphere and investigate its composition and origin.