These Super Earths are located just 150 light years from us and would be terrifying

A study led by researchers from the University of Liège and the CSIC, using observations from NASA’s TESS telescope, presents the detection of a system of two planets slightly larger than Earth that orbit a cold star in a synchronized dance. Called TOI-2096, the system is located 150 light-years from Earth. The discovery is the result of close collaboration between European and American universities and was made possible by the American space mission TESS (Transiting Exoplanet Survey Satellite), whose goal is to find planets orbiting nearby bright stars.

“TESS is conducting an all-sky survey using the transit method, that is, monitoring the stellar brightness of thousands of stars in search of a slight dimming, which could be caused by a planet passing between the star and the observer. However, despite its power to detect new worlds, the TESS mission needs the support of terrestrial telescopes to confirm the planetary nature of the detected signals”, explains Francisco J. Pozuelos, astrophysicist, first author of the article, former member of the ExoTIC laboratory. at the University of Liège, and which has now joined the Higher Council for Scientific Research (IAA-CSIC).

The planets TOI-2096 b and TOI-2096 c were observed with an international network of terrestrial telescopes, which allowed their confirmation and characterization. Most of the transits were obtained with telescopes from the TRAPPIST and SPECULOOS projects led by the University of Liège.

“Doing a thorough analysis of the data, we found that the two planets were in resonant orbits: for every orbit of the outer planet, the inner planet goes around the star twice,” says Mathilde Timmermans, a PhD student in the ExoTIC lab at ULiege. and second author of the article published in the journal Astronomy & Astrophysics.

“Hence their periods are very close to being multiples of each other with around 3.12 days for planet b and around 6.38 days for planet c. This is a very particular configuration and causes a strong gravitational interaction between the planets. This interaction slows or speeds up the passage of planets in front of their star and could lead to the measurement of planetary masses using larger telescopes in the near future.” The researchers behind the discovery estimate that the radius of planet b, the closest to its star, is 1.2 times that of Earth, hence the name ‘super-Earth’. Its properties could be similar to those of Earth: a planet with a mostly rocky composition, possibly surrounded by a thin atmosphere. Similarly, the radius of planet c is 1.9 times the radius of Earth and 55% that of Neptune, which could place the planet in the category of ‘mini-Neptunes’, planets composed of a rocky core and ice cream surrounded by extended hydrogen. or water-rich atmospheres, like Uranus and Neptune in our solar system.

These sizes are very interesting because the number of planets with a radius between 1.5 and 2.5 Earth radii is smaller than theoretical models predict, making these planets a rarity.

“These planets are of crucial importance given their size,” says Mathilde Timmermans, “the formation of super-Earths and mini-Neptunes remains a mystery today. There are several formation models that try to explain it, but none fit the observations perfectly. TOI-2096 is the only system found to date that has a super-Earth and a mini-Neptune in precisely the sizes where the models contradict each other, in other words, TOI-2096 may be the system we have been looking for to understand how these planetary systems have been formed.”

“In addition, these planets are among the best in their category for studying their possible atmospheres,” explains Francisco J. Pozuelos. “Thanks to the relative sizes of the planets with respect to the host star, as well as the brightness of the star, we find this system to be one of the best candidates for a detailed study of its atmosphere with the JWST space telescope. We hope to be able to do it quickly in coordination with other universities and research centers.

source: https://www.aanda.org/articles/aa/full_html/2023/04/aa45440-22/aa45440-22.html