Astronomers have found a super-Earth with a radius of 1.55 Earths in the “conservative zone” of red dwarf TOI-715, 137 light-years from Earth. It falls into the “valley of radii”, a decrease in the radii of discovered exoplanets. On the one hand, red dwarfs (spectral class M stars) can pose a danger to the habitability of exoplanets due to frequent explosions. Thus, computer modeling showed that most planets of the promising TRAPPIST-1 system have probably lost their atmospheres due to the activity of their stars.

Cool red dwarfs are among the best targets for finding Earth-like exoplanets with existing instruments. First, small exoplanets flying against the background of a star create a visible “trough” in the star’s radiation due to the star’s small radius. Second, the orbital period of such objects is also relatively short, making data collection easier.

Red dwarf TOI-715 is located 137 light-years (42 parsecs) away from us. Judging by the spectrum, this is a relatively old star; At least the same age as the Sun, most likely older.

In 2019, astronomers reported a nearby candidate exoplanet; a super-Earth with an orbital period of approximately 19.2 Earth days. Such parameters made it a promising object for further observations. And so the scientists presented the results of the analysis of the data received. They are published on: Monthly Notices of the Royal Astronomical Society.

It turns out that planet TOI-715 b falls in the “conservative zone,” which is the region around the star where the rocky planet receives 0.42 to 0.842 of Earth’s solar energy, the radiation our planet receives from the Sun. . This is the first confirmed exoplanet discovered by the TESS space telescope, and it falls in a region with such tight restrictions.

Another important feature is that the radius of the exoplanet is 1.55 of the radius of the Earth. It turned out that the planet fell into the “radius valley” or “Fulton gap”. These terms refer to the “disadvantage” of exoplanets with orbital periods less than 100 days and radii 1.5-2 times that of Earth. It was detected as a result of analysis of 900 systems discovered by the Kepler space observatory.

Scientists hypothesize that the “radius valley” arose due to different paths of planetary evolution. Evolution depends on both internal processes and the influence of the star, determined by its mass and other parameters. Most importantly, astronomers are not yet sure whether a “Fulton gap” exists in red dwarfs. This is why TOI-715 b is so remarkable; It will help determine the shape and “depth” of this “gap” in such stars.

Also, another hypothesis regarding exoplanets in red dwarfs has recently emerged. Perhaps there is a “gap” between them not in radii but in the density of planets that appear between the rocky and “water worlds”. And it can be explained by various evolutions. Overall, TOI-715 b is a good object to observe with the James Webb Telescope.

While analyzing observational data, the authors of the new study discovered signs of the existence of another small exoplanet in the red dwarf system TOI-715. Moreover, according to estimates, this planet is very close to the Earth, with a size of 1,066 Earth radii. Its orbital period is 25.6 Earth days. It enters the residential area near its outer edge. If the existence of an exoplanet is confirmed, it would be the smallest planet in the region discovered by TESS.