Free Astronomy Magazine May-June 2021

MAY-JUNE 2021 I n this Space Sparks episode, ESA/Hubble summarises an exciting new discovery from the NASA/ESA Hubble Space Telescope. [Directed by: Bethany Downer and Nico Bartmann. Editing: Nico Bartmann. Web and technical support: Enciso Systems. Written by: Bethany Downer. Music: STAN DART – Organic Life (Music written and performed by STAN DART). Footage and photos: ESA/Hubble & NASA, R. Hurt (IPAC/Caltech)] P ictured here is the region around the host star of the exoplanet GJ 1132 b. [ESA/Hubble, Digitized Sky Survey 2. Ack: Davide De Martin] Laboratory. “Then the star cools down and the planet’s just sitting there. So you’ve got this mechanism that can cook off the atmosphere in the first 100 million years, and then things settle down. And if you can regenerate the atmosphere, maybe you can keep it.” In some ways, GJ 1132 b has various parallels to Earth, but in some ways it is also very different. Both have similar densities, similar sizes, and similar ages, being about 4.5 billion years old. Both started with a hydro- gen-dominated atmosphere, and both were hot before they cooled down. The team’s work even sug- gests that GJ 1132 b and Earth have similar atmospheric pressure at the surface. However, the planets’ formation his- tories are profoundly different. Earth is not believed to be the sur- viving core of a sub-Neptune. And Earth orbits at a comfortable dis- tance from our yellow dwarf Sun. GJ 1132 b is so close to its host red dwarf star that it completes an orbit the star once every day and a half. This extremely close proximity keeps GJ 1132 b tidally locked, showing the same face to its star at all times — just as our moon keeps one hemi- sphere permanently facing Earth. “The question is, what is keeping the mantle hot enough to remain liquid and power volcanism?” asked