Scientists are puzzling over another oddball on the edge of the solar system: This time, it’s an icy object less than a quarter of Pluto’s size with a thin atmosphere – a layer of gas that’s not typically found around objects so small.
A Japanese team of researchers — including an amateur astronomer — laid out the curious case of 2002 XV93 this week in the journal Nature Astronomy. 2002 XV93 traces an elliptical path beyond the orbit of Neptune in the icy Kuiper Belt, never coming closer to the sun than 3 billion miles. Like Pluto, it’s locked in a resonance with Neptune that keeps its orbit relatively stable.
The Japanese astronomers, led by Ko Arimatsu of the National Astronomical Observatory of Japan, tracked the mini-world with several telescopes as it passed in front of a background star in January 2024. They found that the light from the star gradually dimmed before it disappeared behind 2002 XV93, as if the light was filtered through a thin layer of gas.
That finding posed a puzzle: Based on estimates of its size, 2002 XV93 shouldn’t have enough gravitational pull to hold onto an atmosphere for longer than, say, 1,000 years.
