A Super-Earth (and Possible Earth-Sized) Exoplanet Found in the Habitable Zone
Artist depiction of the surface of a super-Earth orbiting a red dwarf.
ESO/M. Kornmesser
Astronomers have found a new Super-Earth orbiting an M-dwarf (red dwarf) star about 137 light-years away. The planet is named TOI-715b, and it’s about 1.55 Earth’s radius and is inside the star’s habitable zone. There’s also another planetary candidate in the system. It’s Earth-sized, and if it’s confirmed, it will be the smallest habitable zone planet TESS has discovered so far.
TOI-715 is an average red dwarf. It’s about one-quarter the mass and about one-quarter the radius of our Sun. TOI-715b is close to the star, and its tight orbit takes only 19 days to complete one trip around the dwarf star. Since red dwarfs are much dimmer than the Sun, this puts the Super-Earth in the star’s conservative habitable zone.
New research published in the Monthly Notices of the Royal Astronomical Society presents the discovery. It’s titled “A 1.55 Earth-radius habitable-zone planet hosted by TOI-715, an M4 star near the ecliptic South Pole.” The lead author is Georgina Dransfield, from the School of Physics & Astronomy at the University of Birmingham.
The habitable zone is a rather crude way to identify planets that may have liquid water. Its boundaries are unclear and even contradictory since stellar spectral type, planetary albedo, mass, and even how cloudy its atmosphere is can determine if a planet has liquid water.