A tiny icy rock is defying the laws of gravity
In short: In the freezing reaches of the outer solar system, objects are usually expected to be airless. Yet, a small body called 2002 XV93 has shocked astronomers by clinging to an atmosphere that shouldn't exist. It challenges our understanding of how dynamic these distant worlds truly are.
The discovery centers on 2002 XV93, a trans-Neptunian object (TNO) located far beyond Neptune's orbit within the Kuiper Belt. Measuring approximately 500 km across—significantly smaller than Pluto, which spans 2,377 km—the object is technically classified as a 'plutino.' Under standard astronomical models, bodies of this size and distance are expected to be airless because their surface gravity is too weak and the temperatures are too low to retain gases.
On January 10, 2024, a team led by Ko Arimatsu at the NAOJ Ishigakijima Astronomical Observatory utilized a rare stellar occultation. Observers in Japan tracked starlight while 2002 XV93 moved across a distant star's position. If the object were bare rock and ice, the light would have vanished abruptly; instead, instruments recorded a smooth change in brightness lasting about 1.5 seconds near the edge of the shadow, indicating that the starlight was being bent by a thin layer of gas.
The mystery deepens because calculations suggest this atmosphere is short-lived, potentially vanishing within about 1,000 years unless it is constantly replenished by some unknown mechanism. While Pluto is currently the only known TNO with a confirmed atmosphere, the presence of one around 2002 XV93 suggests that these icy worlds may be far more geologically or chemically active than previously assumed. This finding forces scientists to reconsider the evolution and dynamics of small bodies in the solar system's outer reaches.
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Sources
- Summary by Intellect · source: Tiny Rock In the Solar System Contains Atmosphere and Nobody Knows Why
- Also: This tiny outer Solar System world has an atmosphere. It shouldn’t
- Also: This Tiny Celestial Body Past Pluto Shouldn't Have an Atmosphere—but Astronomers Say They May Have Detected One
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