The two super-Earths orbit a small, cool star about 100 light-years from our planet. The star, LP 890-9, hosts two exoplanets named LP 890-9b and LP 890-9c, the first of which was initially detected by NASA’s Transiting Exoplanet Survey Satellite (TESS). It is the second coldest star that hosts planets, after the famous TRAPPIST-1.
This rare discovery appears thanks to an international team of researchers in the journal Astronomy & Astrophysics . In their study, the scientists show that LP 890-9b, the inner planet of the system , is about 30% larger than Earth and completes one orbit around the star in just 2.7 days. The initial planet candidate was confirmed and characterized by the SPECULOOS ( Search for habitable Planets EClipsing ULtra-cOOl Stars) telescopes that are installed at ESO’s Paranal Observatory in Chile and on the island of Tenerife. Their cameras are very sensitive to the light emitted by cooler stars, so they can observe them with very high precision.
“TESS searches for exoplanets using the transit method , monitoring the brightness of thousands of stars simultaneously, looking for slight dimming that may be caused by planets passing in front of their stars,” explains Laetitia Delrez, postdoctoral researcher at the University of Liège, and lead author of the study. “However, follow-up with ground-based telescopes is often necessary to confirm the planetary nature of detected candidates and refine measurements of their sizes and orbital properties.”
Using the SPECULOOS telescopes to search for additional transiting planets in the system that TESS might have missed, they found precisely the other warm rocky world. LP 890-9c is about 40 percent larger than Earth and has a longer orbital period of about 8.5 days, putting it in the “habitable zone” around its star.
“The habitable zone is a concept according to which a planet with geological and atmospheric conditions similar to those of Earth would have a surface temperature that would allow water to remain liquid for billions of years. “This gives us a license to observe more and find out if the planet has an atmosphere and , if so, study its content and assess its habitability” , the experts clarify.
The SPECULOOS telescopes detected the second outer planet LP 890-9c while observing its star, so the researchers renamed it SPECULOOS-2c . The fact that it has been associated with the habitable zone around its star means it is neither too hot nor too cold for extraterrestrial life, but before it can be confirmed habitable, researchers will need to study its atmosphere, possibly using the James Webb telescope.
“It is important to detect as many temperate terrestrial worlds as possible to study the diversity of exoplanet climates and finally be in a position to measure how often biology has arisen in the Cosmos,” added Amaury Triaud , professor of exoplanetology at the University of Birmingham and co-author of the study.
Referencia: Two temperate super-Earths transiting a nearby late-type M dwarf
L. Delrez, C.A. Murray, F.J. Pozuelos, N. Narita, E. Ducrot, M. Timmermans, N. Watanabe, A.J. Burgasser, T. Hirano, B.V. Rackham, K.G. Stassun, V. Van Grootel, C. Aganze, M. Cointepas, S. Howell, L. Kaltenegger, P. Niraula, D. Sebastian, et al.
A&A, Forthcoming article
Received: 17 May 2022 / Accepted: 22 August 2022