Prominent mid-infrared excess of the dwarf planet (136472) Makemake discovered by JWST/MIRI indicates ongoing activity

TL;DR

This paper reports the discovery of a significant mid-infrared excess around dwarf planet Makemake, suggesting ongoing activity or a ring, which indicates unprecedented phenomena among trans-Neptunian objects.

Contribution

It presents the first detection of a prominent mid-infrared excess around Makemake, proposing new explanations for its origin involving activity or a dust ring.

Findings

Detection of a 150 K temperature excess at Makemake.

Possible evidence of subsurface activity or a dust ring.

Implications for understanding trans-Neptunian object phenomena.

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. The excess, detected by the MIRI instrument of the James Webb Space Telescope, along with previous measurements from the Spitzer and Herschel space telescopes, indicates the occurrence of temperatures of about 150 K, much higher than what solid surfaces at Makemake's heliocentric distance could reach by solar irradiation. We identify two potential explanations: a continuously visible, currently active region, powered by subsurface upwelling and possibly cryovolcanic activity, covering <1% of Makemake's surface, or an as yet undetected ring containing very small carbonaceous dust grains, which have not been seen before in trans-Neptunian or Centaur rings. Both scenarios point to unprecedented phenomena among trans-Neptunian objects and could greatly impact our understanding of these distant worlds.