• The trans-Neptunian object (612533) 2002 XV93, about 500 km in diameter, has mysteriously developed a thin atmosphere (exosphere) in the Kuiper belt.
  • The atmosphere was detected using a combination of professional and amateur telescopes, with a surface pressure of 100-200 nanobars, millions of times thinner than Earth’s.
  • Possible causes include cryovolcanism or a recent impact, as such a thin atmosphere would otherwise dissipate within a thousand years.
  • The composition is unknown; it is speculated to be nitrogen with traces of methane and carbon monoxide, but JWST found no evidence of these ices on the surface.
  • Future observations of atmospheric density over years will help determine its origin: a decrease would suggest an impact, while constant density would indicate ongoing outgassing.
  • The research results were published in Nature Astronomy.

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