Hubble Space Telescope Discovers Exoplanet Forming A New Atmosphere

Astronomers using the NASA/ESA Hubble Space Telescope have discovered a rocky exoplanet orbiting a distant star that shows evidence of volcanic activity that's actively reforming the atmosphere. The planet is known as GJ 1132 b, and scientists believe it has a similar density, size, and age as Earth. One of the most interesting things about GJ 1132 b is that scientists believe it started as a gaseous world with a thick atmosphere.

Originally, the planet was several times the Earth's radius and was a planet known as a "sub-Neptune." The planet lost its primordial hydrogen and helium atmosphere due to intense radiation from the hot, young start it orbits. The planet's atmosphere stripped away, leaving a bare core about the size of Earth.

Recent Hubble observations have uncovered a secondary atmosphere that has replaced part of the original atmosphere the planet had. The secondary atmosphere is rich in hydrogen, hydrogen cyanide, methane, and ammonia. Data also shows the planet has a hydrocarbon haze.

Scientists believe the original atmosphere was absorbed into the planet's molten magma mantle and is now being slowly released by volcanism to form a new atmosphere. While the second atmosphere is leaking into space, it is continually being replenished from hydrogen in the planet's magma.

The continually replenishing atmosphere is described as a window into the geology of another world. Observations of GJ 1132 b also have scientists wondering how many terrestrial planets don't begin that way. They may start as sub-Neptunes and become terrestrial planets when their primordial atmospheres evaporate. GJ 1132 b is so close to his host star, a red dwarf, that it completes an orbit around the star once every day and a half. It's also tidally locked with the same side facing its star all the time.