A Japanese consortium of astronomers has ascertained the presence of a tenuous atmosphere encircling (612533) 2002 XV93, a trans-Neptunian celestial body measuring approximately 500 kilometers in diameter—a size and temperature profile that would typically preclude atmospheric retention.
An artist’s conception of the trans-Neptunian object 2002 XV93. Image credit: NAOJ.
“Within the frigid confines of our solar system’s outer reaches reside myriad diminutive entities designated as trans-Neptunian objects (TNOs) due to their orbital paths lying beyond that of Neptune,” commented Dr. Ko Arimatsu of the Ishigakijima Astronomical Observatory, alongside his research associates.
“While a rarefied atmosphere has been documented around Pluto, the most renowned TNO, investigations into other TNOs have thus far produced negative findings.”
“The majority of TNOs are so profoundly cold, and their surface gravity so attenuated, that they are not anticipated to sustain atmospheres.”
The celestial researchers conducted their investigation of the trans-Neptunian object 2002 XV93 by employing a stellar occultation technique, meticulously quantifying the transient diminution of a background star’s luminosity as the TNO traversed its line of sight.
“2002 XV93 possesses a diameter estimated at roughly 500 kilometers. For comparative context, Pluto’s diameter is 2,377 kilometers,” the scientists elucidated.
“Due to its orbital characteristics, 2002 XV93, as observed from Earth, performed a direct transit across a star on January 10, 2024.”
“As the stellar source vanishes behind 2002 XV93, its light might gradually wane, signifying attenuation as it permeates a thin gaseous envelope; alternatively, it could abruptly extinguish as it disappears behind the solid expanse of the TNO.”
The investigative team concluded that the observational data are most convincingly interpreted as indicative of a tenuous atmosphere enveloping 2002 XV93.
Their computational models suggest that such an atmosphere would likely dissipate within a millennium unless it receives a continuous source of replenishment.
This implies that its formation—or reconstitution—must have occurred in the relatively recent past.
“Analyses conducted by the NASA/ESA/CSA James Webb Space Telescope reveal no evidence of frozen volatiles on the surface of 2002 XV93 that could undergo sublimation to generate an atmosphere,” the authors stated.
“One plausible explanation posits that an event may have transported frozen or liquefied gases from the interior of the TNO to its surface.”
“An alternative hypothesis suggests the impact of a comet with 2002 XV93, leading to the release of gases that established a temporary atmospheric shell.”
“Additional observational endeavors are necessitated to accurately differentiate between these two potential causal mechanisms.”
“This groundbreaking discovery underscores the capability of even a few-hundred-kilometer TNO to harbor, at least temporarily, an atmosphere, thereby challenging conventional paradigms of volatile retention,” they concluded.
“Our findings indicate that a subset of distant icy minor planets may exhibit atmospheres, potentially sustained by ongoing cryovolcanic processes or the consequence of a recent collision with a small icy body.”
The researchers’ published work appeared in the esteemed journal Nature Astronomy.
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K. Arimatsu et al. Detection of an atmosphere on a trans-Neptunian object beyond Pluto. Nat Astron, published online May 4, 2026; doi: 10.1038/s41550-026-02846-1
