Recent research reveals that a small, icy celestial body located in the Kuiper Belt, comparable to Pluto, possesses an atmosphere.

This object, designated as (612533) 2002 XV93, marks its discovery nearly 25 years ago and has a diameter under 500 kilometers.

It is classified within the Plutino group, sharing a similar stable orbit with Pluto, completing three solar revolutions for every two of Neptune.

On January 10, 2024, (612533) 2002 XV93 caused an occultation, passing in front of a distant star. A team led by Wataru Arimatsu at Kyoto University monitored this event across three locations in Japan.

If there were no atmosphere, the star’s light would have blinked away almost instantaneously as it obscured 2002 XV93.

However, the researchers noticed that the star’s light gradually faded and returned within approximately 1.5 seconds at the shadow’s edge.

“This gradual change suggests that starlight is being refracted by a thin atmosphere enveloping 2002 XV93,” explains Arimatsu.

The team estimates a surface pressure of 100 to 200 nanobars—dramatically thinner than Earth’s atmosphere, approximately 5 to 10 million times less, and about 50 to 100 times thinner than Pluto’s atmosphere.

“I couldn’t breathe, feel the wind, or see anything reminiscent of Earth’s sky,” said Arimatsu. “Nonetheless, this thin atmosphere significantly bends starlight, indicating the presence of volatile gases around small icy bodies.”

While the exact composition of the atmosphere remains undetermined, Arimatsu speculates that methane, nitrogen, and carbon monoxide could be potential constituents, as these gases are highly volatile even under the frigid temperatures of the outer solar system.

Another question arises regarding the gas emissions from the interior of 2002 XV93, potentially suggesting volcanic activity or a result of cosmic collisions.

“This discovery reshapes our understanding of small celestial bodies in the outer solar system,” Arimatsu asserts. “Traditionally, detectable atmospheres were believed to be exclusive to planets, dwarf planets, and a select few large moons. 2002 XV93 stands as one of the smallest known celestial objects with a clearly detectable atmosphere.”

Astonished, Ben Montet from the University of New South Wales in Sydney remarked, “If one stood on this icy surface, they wouldn’t see a sky like ours. This challenges the belief that even the faintest atmosphere cannot exist on small celestial bodies.”

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