A team of Japanese astronomers has discovered a thin atmosphere surrounding the trans-Neptunian object (612533) 2002 XV93, which has an approximate diameter of 500 km. This celestial body is too small and cold to retain a substantial atmosphere.
Artist’s conception of trans-Neptunian object 2002 XV93. Image by: National Astronomical Observatory of Japan
“The cold regions of the outer solar system host thousands of small bodies known as trans-Neptunian objects (TNOs) because they orbit outside Neptune.” according to Dr. Ko Arimatsu from Ishigakijima Observatory.
“While Pluto, the most well-known TNO, has been observed with a thin atmosphere, studies of other TNOs generally yield negative results.”
“Most TNOs are extremely cold and possess weak surface gravity, making it unlikely for them to maintain an atmosphere.”
Astronomers utilized stellar occultation to study trans-Neptunian object 2002 XV93, measuring its light fluctuations as background stars passed behind it.
“With a diameter of around 500 km, 2002 XV93 is significantly smaller than Pluto, which has a diameter of 2,377 km,” they noted.
“On January 10, 2024, 2002 XV93’s orbit caused it to briefly obscure a background star.”
“As the star gradually dimmed while being obscured by 2002 XV93, it indicated the possibility of light attenuation due to the thin atmosphere, or a sudden disappearance as it moved behind the solid surface of the TNO.”
The researchers concluded that the observed behavior best supports the existence of a thin atmosphere around 2002 XV93.
They estimate that this atmosphere could vanish in approximately 1,000 years unless it is replenished in some manner.
This suggests that the atmosphere must have formed or been replenished relatively recently.
“Observations with the NASA/ESA/CSA James Webb Space Telescope reveal no indications of frozen gas that could sublimate to create an atmosphere on 2002 XV93,” the authors stated.
“One hypothesis is that deep internal processes brought frozen or liquid gas to the surface of the TNO.”
“Alternatively, a comet may have collided with 2002 XV93, releasing gas and forming a temporary atmosphere.”
“Further investigations are essential to clarify these possibilities.”
“This finding sheds light on the potential for even smaller TNOs to temporarily harbor atmospheres, challenging conventional volatile retention models,” the researchers concluded.
“Our results imply that some distant icy bodies could be sustained by ongoing cryovolcanism or exhibit atmospheres formed by recent impacts from small icy objects.”
The team’s research paper was published in the journal Nature Astronomy.
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Kazuya Arimatsu et al.. Discovery of the atmosphere surrounding a trans-Neptunian object beyond Pluto. Nat Astron, published online on May 4, 2026. doi: 10.1038/s41550-026-02846-1
Source: www.sci.news
