Astronomers Report Possible Very Thin Atmosphere on Kuiper Belt Object 2002 XV93

Astronomers have detected a thin atmosphere on the trans-Neptunian object (612533) 2002 XV93, one of the smallest solar system bodies yet with a clearly detected atmosphere. The object, located in the Kuiper Belt, passed in front of a distant star on 10 January 2024, causing an occultation. Ko Arimatsu at Kyoto University and his colleagues observed the event from three locations in Japan.

5 seconds near the edge of the shadow of 2002 XV93. “These gradual changes are best explained if the star’s light was bent by a very thin atmosphere around 2002 XV93,” says Ko Arimatsu. The team estimates a surface pressure of about 100 to 200 nanobars on 2002 XV93.

That pressure is 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 belongs to the class of objects known as plutinos.

Plutinos are in the same stable orbit as Pluto, completing three revolutions around the sun for every two made by Neptune. The object was formally named after the date of its discovery nearly a quarter of a century ago. It has a diameter of less than 500 kilometres.

The team could not determine the composition of the atmosphere directly from the data. Methane, nitrogen and carbon monoxide are the most plausible candidates for the atmosphere because they are volatile enough to become gases at the very low temperatures of the outer solar system.

Possibilities for what caused the atmosphere include volcanic activity, outgassing from the interior of 2002 XV93 or even a cosmic collision.

“This discovery challenges our conventional view of small worlds in the outer solar system,” says Arimatsu. “Until now, clearly detectable atmospheres in the solar system were associated with planets, dwarf planets and some large satellites. ” He added that while a person standing on the surface would not see a sky like Earth’s, the finding challenges assumptions about thin atmospheres on small bodies.

1038/s41550-026-02846-1. @NewScientist reported the full details of the observation and its implications.