In recent years, a comprehensive study of red dwarf stars has been conducted to find exoplanets orbiting them. These stars have effective surface temperatures between 2400 and 3700 K (more than 2000 degrees cooler than the Sun) and masses between 0.08 and 0.45 solar masses. In this context, a team of researchers led by Borja Toledo Padrón, Severo Ochoa-La Caixa doctoral student at the Instituto de Astrofísica de Canarias (IAC), specialized in the search for planets around these types of stars, has discovered a super – The Earth orbits the star GJ 740, a red dwarf star located about 36 light years from Earth.
The planet orbits its star with a period of 2.4 days and its mass is about 3 times the mass of Earth. Because the star is so close to the Sun and the planet so close to the star, this new super Earth could be the subject of future research with very large diameter telescopes towards the end of this decade. The results of the study were recently published in the journal Astronomy and Astrophysics.
“This is the planet with the second shortest orbital period around this type of star. The mass and period suggest a rocky planet, with a radius of about 1.4 Earth radii, which could be confirmed in future observations with the TESS satellite ”, explains Borja Toledo Padrón, first author of the article. The data also indicate the presence of a second planet with an orbital period of 9 years, and a mass comparable to that of Saturn (about 100 Earth masses), although its radial velocity signal could be due to the star’s magnetic cycle (similar to that of the Sun), so more data is needed to confirm that the signal is actually due to a planet.
The Kepler mission, recognized as one of the most successful in detecting exoplanets using the transit method (which is the search for small variations in the brightness of a star caused by the transit between it and us of the planets that orbit its around), has discovered a total of 156 new planets around cool stars. From their data, it has been estimated that this type of star hosts an average of 2.5 planets with orbital periods of less than 200 days. “The search for new exoplanets around cool stars is driven by the smaller difference between the mass of the planet and the mass of the star compared to stars in warmer spectral classes (which makes it easier to detect the signals from the planets) , as well as the large number of this type of star in our Galaxy ”, comments Borja Toledo Padrón.
Cool stars are also an ideal target for searching for planets using the radial velocity method. This method is based on the detection of small variations in the speed of a star due to the gravitational attraction of a planet orbiting around it, using spectroscopic observations. Since the discovery in 1998 of the first radial velocity signal from a exoplanet around a cold star, so far, a total of 116 exoplanets have been discovered around this class of stars using the radial velocity method. “The main difficulty of this method is related to the intense magnetic activity of this type of stars, which can produce spectroscopic signals very similar to those of an exoplanet”, says Jonay I. González Hernández, IAC researcher who is co-author of this Article.
Reference: “A super-Earth in close orbit around the star of M1V GJ 740: A collaboration of HADES and CARMENES” by B. Toledo-Padrón, A. Suárez Mascareño, JI González Hernández, R. Rebolo ,, M. Pinamonti , M. Perger, G. Scandariato, M. Damasso, A. Sozzetti, J. Maldonado, S. Desidera, I. Ribas, G. Micela, L. Affer, E. González-Alvarez, G. Leto, I. Pagano , R. Zanmar Sánchez, P. Giacobbe, E. Herrero, JC Morales, PJ Amado, JA Caballero, A. Quirrenbach, A. Reiners and M. Zechmeister, April 7, 2021, Astronomy and Astrophysics.
DOI: 10.1051 / 0004-6361 / 202040099
The study is part of the HADES project (HArps-n Red Dwarf Exoplanet Survey), in which the IAC collaborates with the Institut de Ciències de l’Espai (IEEC-CSIC) of Catalonia, and the Italian program GAPS (Global architecture of planetary systems), whose objective is the detection and characterization of round exoplanets of cold stars, in which they are being used Harps-N, at the Telescopio Nazionale Galileo (TNG) of the Roque de los Muchachos Observatory (Garafía, La Palma). This detection was possible thanks to a six-year observation campaign with HARPS-N, complemented by measurements with the CARMENES spectrograph at the 3.5 m telescope at the Calar Alto Observatory (Almería) and HARPS, at the 3-meter telescope. 6 m from the La Silla Observatory (Chile), as well as photometric support for the ASAP and EXORAP surveys. IAC researchers Alejandro Suárez Mascareño and Rafael Rebolo also participate in this work.