Whereas Earth has always been a terrestrial, rocky world, GJ 1132 b began its life as a gaseous, Neptune-like planet. But as new research shows, a nearby red dwarf obliterated its original hydrogen- and helium-rich atmosphere with powerful radiation, so GJ 1132 b, having been stripped down to its rocky core, is now technically a terrestrial planet. The new paper will appear in an upcoming issue of the Astronomical Journal, but a preprint is available at the arXiv.The authors of the paper reached these conclusions based on direct observations of the exoplanet and theoretical modeling. The telescope of choice was the Hubble Space Telescope, which allowed the team to spot the “secondary atmosphere,” which consists of molecular hydrogen, hydrogen cyanide, methane, and an aerosol haze resembling smog on Earth.
“It’s super exciting because we believe the atmosphere that we see now was regenerated, so it could be a secondary atmosphere,” Raissa Estrela, a co-author of the study and a planetary scientist at NASA’s Jet Propulsion Laboratory in Southern California, explained in a statement. “We first thought that these highly irradiated planets could be pretty boring because we believed that they lost their atmospheres. But we looked at existing observations of this planet with Hubble and said, ‘Oh no, there is an atmosphere there.’
In terms of an explanation, the authors say much of the planet’s current hydrogen was retained from before, having been absorbed into the molten magma mantle. Volcanic processes are now causing this stored hydrogen to leak out from below, refueling the new atmosphere, according to the research.