Small Kuiper Belt Object 2002 XV93 Occults Star, Revealing Possible Very Thin Atmosphere

A trans-Neptunian object less than 500 kilometres in diameter revealed a thin atmosphere when it passed in front of a distant star on 10 January 2024. The object, formally named (612533) 2002 XV93, is located in the Kuiper Belt and belongs to the class known as plutinos. These bodies share the same stable orbit as Pluto, completing three revolutions around the sun for every two made by Neptune.

Ko Arimatsu at Kyoto University and his colleagues observed the occultation from three locations in Japan. 5 seconds near the edge of the shadow. “These gradual changes are best explained if the star’s light was bent by a very thin atmosphere around 2002 XV93,” says Arimatsu.

The team estimates the surface pressure of the atmosphere at about 100 to 200 nanobars. This makes it roughly 5 million to 10 million times thinner than Earth’s atmosphere and about 50 to 100 times thinner than Pluto’s tenuous atmosphere. “You could not breathe it, feel wind from it, or see anything like Earth’s sky,” says Arimatsu.

The object (612533) 2002 XV93 was discovered nearly a quarter of a century before 10 January 2024. @NewScientist reported that methane, nitrogen and carbon monoxide are the most plausible candidates for the atmosphere’s composition because they are volatile enough to become gases at the very low temperatures of the outer solar system.

The team could not determine the composition directly from the occultation data.

Possible causes for the atmosphere include volcanic activity, outgassing from the interior of 2002 XV93 or a cosmic collision. ,” says Arimatsu. ” 2002 XV93 appears to be one of the smallest solar system bodies yet with a clearly detected atmosphere.

Ben Montet at the University of New South Wales in Sydney, Australia, said Ben Montet noted that the result was unexpected for a body of this size. Montet added that a person standing on the surface would not see a sky like Earth’s yet the detection still challenges the assumption that even a thin, transient atmosphere cannot exist on a body this small.

An artist’s impression released by NAOJ/Ko Arimatsu shows the trans-Neptunian object (612533) 2002 XV93 blocking the light from a distant star. 1038/s41550-026-02846-1.