An article published in “The Astronomical Journal” reports a study on two “bare” super-Earths, as they lack a primordial atmosphere. A team of researchers used the Subaru telescope and other instruments for a follow-up study of two candidate exoplanets discovered by NASA’s TESS space telescope and classified as TOI-1634b and TOI-1685b. Both candidates were confirmed and showed some characteristics in common since they’re super-Earths with orbits that are very close to their stars, both red dwarfs, with no primordial atmosphere. Their study will help to understand the evolution of the atmospheres of hot rocky planets.
Launched on April 18, 2018, the TESS Space Telescope is today the leading planet hunter. The candidates, identified by an acronym starting with TOI (TESS Object of Interest), must be verified with other telescopes such as the Subaru. Two confirmed candidates turned out to be interesting for studies on the atmospheres of hot rocky planets because they’re close to their stars, in this case, two red dwarfs whose mass and size are in both cases about half the Sun’s. They’re part of the category of ultra-short period planets because their year lasts less than one Earth day.
About 114 light-years away from Earth, the exoplanet TOI-1634b has a mass estimated to be around 10.14 times the Earth’s for a radius that is almost 1.75 times the Earth’s. These characteristics make it one of the largest and most massive rocky planets known among those with an ultra-short period.
About 122 light-years away from Earth, the exoplanet TOI-1685b has a mass estimated to be just over 3.4 times the Earth’s for a radius that is almost 1.46 times the Earth’s. Its year is really short, as it lasts around 16 Earth hours.
The mass and size estimates of these two exoplanets are consistent with an Earth-like internal composition. In essence, the term super-Earth is appropriate for them. This finding is not surprising because it appears to be a typical composition for ultra-short period exoplanets.
Normally, rocky planets are born with a thick atmosphere of hydrogen and helium. According to some studies, there are cases in which that primordial atmosphere is so large that they are born as mini-Neptunes and then lose most of that gas. The exoplanets TOI-1634b and TOI-1685b are so close to their stars that they probably interacted with them and lost their primordial atmosphere.
A planet can develop what is technically called a secondary atmosphere, made up of gases that are released from inside the planet. TOI-1634b and TOI-1685b are excellent candidates for studying the possibility that ultra-short period planets could develop a secondary atmosphere despite the proximity of their star.
Another research front that makes TOI-1634b and TOI-1685b interesting concerns their origin. Previous studies involving planets very close to their star indicate that they formed in a more distant area of their system and then migrated. Planetary migration is a topic that has been increasingly studied in recent years thanks to the discovery of many planets close to their star.
For these reasons, TOI-1634b and TOI-1685b will continue to be studied and astronomers keep on searching for other exoplanets. The team that studied these two cases participates in the verification of candidates discovered by the TESS space telescope in the hopes of finding more exoplanets that are out of the ordinary.
