A tiny frozen world is defying the laws of gravity
In short: Four billion miles from the Sun, a celestial body only 310 miles wide is doing the impossible: holding onto an atmosphere. Based on its weak gravity, the gas should have leaked into space centuries ago, yet it remains. This discovery challenges our understanding of how inactive the outer solar system truly is.
The object, known as 2002 XV93, is a trans-Neptunian object (TNO) located in the Kuiper Belt. Classified as a 'plutino', this object circles the Sun a pair of times during the period Neptune finishes three revolutions. While Pluto is the only other known TNO with an atmosphere, 2002 XV93 is significantly smaller, with a diameter of approximately 500 km compared to Pluto's 2,377 km. Because it is so small and distant, it lacks the surface gravity and warmth required to retain gases under standard astronomical models. On January 10, 2024, a team of professional and amateur astronomers from the National Astronomical Observatory of Japan captured a rare 'natural experiment.' As 2002 XV93 passed in front of a distant star, instruments recorded a smooth change in the star's brightness lasting about 1.5 seconds. This gradual fade, rather than a sudden disappearance, indicates that starlight was being bent and attenuated by a thin atmosphere. However, the mystery deepens: calculations suggest this atmosphere should escape into space within 100 to 1,000 years, yet the object is roughly 4.5 billion years old. Data from the James Webb Space Telescope has ruled out the presence of frozen gases on the surface that could be sublimating to create this layer. This leaves two primary theories: either a recent collision—such as a comet impact—exposed volatile ices from the interior, or the world is still actively releasing material from deep within its core. Upcoming stellar occultations will determine if the atmosphere is a fleeting ghost or a continuously replenished phenomenon.
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Sources
- Summary by Intellect · source: A Tiny World Beyond Neptune Has An Atmosphere That Shouldn’t Be Possible
- Also: This Tiny Celestial Body Past Pluto Shouldn't Have an Atmosphere—but Astronomers Say They May Have Detected One
- Also: A tiny world beyond Neptune has an atmosphere that shouldn't exist
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