A small icy object beyond Pluto in the Kuiper Belt may have a delicate atmosphere, according to a new study by Japanese astronomers. The body, known as (612533) 2002 XV93 and measuring about 300 miles across, is considered the smallest solar system object confirmed to have a global atmosphere bound by gravity.
The study, published Monday in the journal Nature Astronomy, reports observations made in 2024 using three telescopes in Japan as the object passed in front of a background star. The slight dimming of the star’s light indicated the presence of an atmosphere around this distant celestial body, which orbits the Sun farther than Pluto.
The atmosphere is estimated to be 5 million to 10 million times thinner than Earth’s, and 50 to 100 times less dense than Pluto’s known atmospheric layer. The most likely gases identified include methane, nitrogen, or carbon monoxide—all capable of causing the observed dimming during the occultation event.
Lead researcher Ko Arimatsu of the National Astronomical Observatory of Japan noted the finding challenges the prevailing idea that atmospheres are restricted to larger planets, dwarf planets, or sizable moons. If independently confirmed, this would mark the second known Kuiper Belt object with an atmosphere, following Pluto.
The origin of the atmosphere remains uncertain. The researchers propose it could be the result of ice volcanoes outgassing from the object’s interior or the aftermath of a comet impact, which would suggest the atmospheric gases will dissipate over time.
Some experts urge caution in interpreting the results. Spanish astronomer Jose-Luis Ortiz, who studies trans-Neptunian objects, stated that more data is required to confirm the atmosphere and suggested an alternative explanation such as the presence of a ring system around the object. Arimatsu acknowledged this possibility but said their observations are not consistent with a ring scenario.
Future observations, particularly with NASA’s James Webb Space Telescope, could provide more definitive data on the atmospheric composition and nature of this small Kuiper Belt object.
Why it matters
Confirming an atmosphere on such a small distant object reshapes scientists’ understanding of how atmospheres can form and persist in the cold, distant reaches of the solar system. It could influence models of planetary formation and the diversity of bodies beyond Neptune.
Background
(612533) 2002 XV93 is classified as a plutino, orbiting the Sun twice for every three Neptune orbits. Pluto, once considered the ninth planet but reclassified as a dwarf planet in 2006, remains the only Kuiper Belt body with a definitively observed atmosphere. There have been suggestions of atmospheres on other dwarf planets like Makemake, but these remain debated.
This discovery adds to ongoing studies of the Kuiper Belt, a region of icy bodies that represents some of the solar system’s most primordial remnants. NASA’s New Horizons mission previously provided detailed views of Pluto and the dwarf planet Arrokoth, further stimulating interest in these remote worlds.
Sources
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