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Arxiv: Prominent mid-infrared excess of the dwarf planet (136472) Makemake discovered by JWST/MIRI indicates ongoing activity Published: 10/29/2024 11:21:24 PM Updated: 10/29/2024 11:21:24 PM

Paper abstract: We report on the discovery of a very prominent mid-infrared (18-25 {\mu}m)excess associated with the trans-Neptunian dwarf planet (136472) Makemake. Theexcess, detected by the MIRI instrument of the James Webb Space Telescope,along with previous measurements from the Spitzer and Herschel spacetelescopes, indicates the occurrence of temperatures of about 150 K, muchhigher than what solid surfaces at Makemake's heliocentric distance could reachby solar irradiation. We identify two potential explanations: a continuouslyvisible, currently active region, powered by subsurface upwelling and possiblycryovolcanic activity, covering <1% of Makemake's surface, or an as yetundetected ring containing very small carbonaceous dust grains, which have notbeen seen before in trans-Neptunian or Centaur rings. Both scenarios point tounprecedented phenomena among trans-Neptunian objects and could greatly impactour understanding of these distant worlds.