Rocky exoplanet TRAPPIST-1 b (illustration)

Illustration showing what the hot rocky exoplanet TRAPPIST-1 b could look like. TRAPPIST-1 b, the innermost of seven known planets in the TRAPPIST-1 system, orbits its star at a distance of 0.011 AU, completing one circuit in just 1.51 Earth-days. TRAPPIST-1 b is slightly larger than Earth, but has around the same density, which indicates that it must have a rocky composition. Webb’s measurement of mid-infrared light given off by TRAPPIST-1 b suggests that the planet does not have any substantial atmosphere. The star, TRAPPIST-1, is an ultracool red dwarf (M dwarf) with a temperature of only 2566 K and a mass just 0.09 times the mass of the Sun.

This illustration is based on new data gathered by Webb’s Mid-Infrared Instrument (MIRI) as well as previous observations from other ground- and space-based telescopes. Webb has not captured any images of the planet.

MIRI was developed as a partnership between Europe and the USA: the main partners are ESA, a consortium of nationally funded European institutes, the Jet Propulsion Laboratory (JPL) and the University of Arizona. The instrument was nationally funded by the European Consortium under the auspices of the European Space Agency. 

[Image description: Illustration of a rocky planet and its red dwarf star on an empty black background. The planet is large, in the foreground on the lower right and the star is smaller, in the background at the upper left. The planet is various shades of grey, with some small craters. There is no apparent atmosphere. The left quarter of the planet (the side facing the star) is lit, while the rest is in shadow.]