16 articles · Updated · The Associated Press · May 4
Using three telescopes in Japan, researchers observed a 2024 stellar occultation and found the 500km-wide object may be the smallest body known with a gravity-bound global atmosphere.
The study in Nature Astronomy says the atmosphere is 5 million to 10 million times thinner than Earth's and likely contains methane, nitrogen or carbon monoxide.
Scientists say the gases may come from ice volcanism or a comet impact, and future monitoring, including with the Webb telescope, could test whether the atmosphere persists, varies seasonally or fades.
How will tomorrow's observation of Haumea confirm if tiny, distant worlds can truly host atmospheres?
Is this tiny world's atmosphere a ghost from an impact or a sign of active ice volcanoes from within?
Could thousands of tiny worlds with atmospheres be hiding in the Kuiper Belt, rewriting our map of the solar system?
Detecting a 5 to 10 Million Times Thinner Atmosphere on Tiny Trans-Neptunian Object 2002 XV93
Overview
In 2024, astronomer Ko Arimatsu's team discovered a surprisingly thin atmosphere around the small trans-Neptunian object 2002 XV93 using the stellar occultation method, which revealed gradual dimming of starlight caused by atmospheric refraction. This atmosphere, composed mainly of methane, nitrogen, and carbon monoxide, is 5 to 10 million times thinner than Earth's and would quickly dissipate without replenishment. Possible sources include internal cryovolcanism, potentially driven by tidal heating from Neptune's resonance, or comet impacts delivering and releasing volatile ices. This finding challenges the belief that only large bodies can hold atmospheres, suggests such thin atmospheres may be common among distant icy objects, and calls for JWST observations to study its composition and evolution, offering new insights into outer solar system activity and small exoplanet atmospheres.