Free Astronomy Magazine May-June 2021

21 MAY-JUNE 2021 ASTRO PUBLISHING tinues to leak away into space, is continually being replenished from the reservoir of hydrogen in the mantle’s magma. “This second atmosphere comes from the surface and interior of the planet, and so it is a window onto the geology of another world,” ex- plained team member Paul Rimmer of the University of Cambridge, UK. “A lot more work needs to be done to properly look through it, but the discovery of this window is of great importance.” “We first thought that these highly radiated planets would be pretty boring because we believed that they lost their atmospheres,” said team member Raissa Estrela of the Jet Propulsion Laboratory at the Cal- ifornia Institute of Technology in Pasadena, California, USA. “But we looked at existing observations of this planet with Hubble and realised that there is an atmosphere there.” “How many terrestrial planets don’t begin as terrestrials? Some may start as sub-Neptunes, and they become terrestrials through a mechanism whereby light evaporates the pri- mordial atmosphere. This process works early in a planet’s life, when the star is hotter,” said team leader Mark Swain of the Jet Propulsion T his image is an artist’s impression of the exoplanet GJ 1132 b. [NASA, ESA, and R. Hurt (IPAC/Caltech)]