A rare observation of 2002 XV93, a trans-Neptunian body about 500 km in diameter, has revealed signs of a very thin atmosphere. Researchers estimate that it should dissipate in less than a thousand years, so it may have been formed or regenerated recently due to internal activity or impact with another icy body.
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2002 XV93, trans-Neptunian body, outer solar system, Kuiper belt, Pluto, thin atmosphere, star occultation, James Webb Space Telescope, NAOJ, astronomy
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Small body beyond Neptune discovered with thin atmosphere
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Astronomers have detected signs of a thin atmosphere around 2002 XV93, a small body beyond Neptune. The discovery raises questions about activity in the outer solar system.
A small world in our solar system has an atmosphere it shouldn't have, a hint that something dramatic happened there recently.
A team of Japanese astronomers, including professional and amateur observers, has found signs of a thin atmosphere circling a small body far beyond Neptune. The discovery is surprising because the body is so small that it shouldn't be able to hold on to gas for long. It raises new questions: when did the atmosphere form and what keeps it there. More observations will be needed to better understand this unusual discovery.
The reason most trans-Neptunian bodies are airless
The outer solar system is full of icy bodies called trans-Neptunian objects (TNOs), which orbit the Sun beyond Neptune. Pluto is the best-known example and one of the few with a confirmed thin atmosphere. But for most TNOs, conditions make the existence of an atmosphere unlikely. These bodies are very cold, and their weak gravity allows gases to escape easily, leaving the surface exposed to space.
A rare passage provides a clue
An illustrative video showing how light from a star changes as it passes behind a body with an atmosphere. Credit: NAOJ
To further investigate, the scientists took advantage of a "natural experiment" related to a TNO called (612533) 2002 XV.93The diameter of this body, whose short name is 2002 XV93, is about 500 km across, much smaller than Pluto, which has a diameter of 2,377 km.
On 10.1.24, 2002 XV93 Passed directly in front of a distant star as seen from Japan. Such events allow scientists to study distant objects in detail. If the object has no atmosphere, the star's light should disappear immediately. If it is surrounded by gas, the light gradually dims as it passes through the atmosphere before disappearing.
Observations reveal signs of a thin atmosphere
A team monitored this event from several locations in Japan. Their measurements showed a pattern of dimming starlight consistent with the presence of a thin atmosphere. This suggests that 2002 XV93 Not as completely exposed as previously expected.
A short-lived atmosphere of unknown origin
Further analysis shows that this atmosphere cannot last long. Calculations indicate that it will dissipate in less than a thousand years if new material is not regularly added. This means that the atmosphere must have been created or regenerated in the recent past.
Observations from the James Webb Space Telescope add to the mystery. They show no clear evidence of ice on the surface that could slowly turn to gas and sustain the atmosphere. Scientists are now considering other explanations. One idea is that material from inside the star reached the surface and released gas. Another possibility is that a colliding comet provided gas or caused the release of gas, creating a temporary atmosphere.
More data is needed to determine which explanation is correct and to understand how such a small body could even support an atmosphere for a short time.
for the scientific article DOI: 10.1038/s41550-026-02846-1
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Short FAQ
What is 2002 XV93?
2002 XV93 is a small trans-Neptunian body, that is, an icy body that orbits the Sun beyond the orbit of Neptune.
Why is the discovery surprising?
The body is much smaller than Pluto, so its gravity is too weak to hold an atmosphere for long.
How was the atmosphere discovered?
On January 10, 2024, the object passed in front of a distant star as seen from Japan. The star's light gradually dimmed, a pattern consistent with a passage through a thin atmosphere rather than a sharp disappearance behind an airless object.
One response
It is possible that this atmospheric presence has something to do with the density of this body. If, for the sake of assumption, we accept the hypothesis that the density of this body, for example, is 4 g/cm3, we will obtain some atmospheric presence, even if it is sparse. Only future observations will allow us to measure the density.