Artistic impression of the super-Earth orbiting the red dwarf star GJ-740. Credit: Gabriel Pérez Díaz, SMM (IAC)
In recent years there has been an exhaustive study of red dwarf stars to find exoplanets in orbit around them. These stars have effective surface temperatures between 2400 and 3700 K (over 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, doctoral student Severo Ochoa-La Caixa at the Instituto de Astrofísica de Canarias (IAC), specialized in searching for planets around this type of star, discovered a super-Earth orbiting. the star GJ 740, a red dwarf star located about 36 light-years from Earth.
The planet orbits its star for a period of 2.4 days, and its mass is about 3 times greater than the mass of the 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 by 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. Mass and period suggest a rocky planet with a radius of about 1.4 Earth rays, which could be confirmed in future observations with TESS satellite ”, explains Borja Toledo Padrón, the 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 (almost 100 Earth masses), although its radial velocity signal may 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 indeed due to a planets.
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 a star’s brightness caused by the transit between it and us of planets orbiting it), discovered a total of 156 of new planets around cold stars. From its data, it has been estimated that this type of star shelters an average of 2.5 planets with orbital periods of less than 200 days. “The search for new exoplanets around cold stars is driven by the smaller difference between the planet’s mass and the star’s mass compared to stars in warmer spectral classes (which makes it easier to detect planetary signals), as well as the large number of this star in the galaxy.” ours ”, comments Borja Toledo Padrón.
Cold stars are also an ideal target for searching for planets by the radial velocity method. This method is based on detecting small variations in the speed of a star due to the gravitational attraction of a planet in its orbit around it, using spectroscopic observations. Since the discovery in 1998 of the first radial velocity signal of a exoplanet Around a cool 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 star, which can produce spectroscopic signals very similar to those due to an exoplanet,” says Jonay I. González Hernández, an IAC researcher who co-authored this article.
Reference: “A super-Earth in a close orbit around the star 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, 7 April 2021, Astronomy and astrophysics.
DOI: 10.1051 / 0004-6361 / 202040099
The study is part of the HADES project (HArps-n Red Surop Exoplanet Survey), in which IAC collaborates with Institute of Space Sciences (IEEC-CSIC) in Catalonia and the Italian GAPS program (The global architecture of planetary systems), whose objective is the detection and characterization of round star exoplanets, in which they are used HARPS-N, on the Telescopio Nazionale Galileo (TNG) at the Roque de los Muchachos Observatory (Garafía, La Palma). This detection was made possible by a six-year observation campaign with HARPS-N, supplemented by measurements with the CARMENES spectrograph on the 3.5 m telescope at the Calar Alto Observatory (Almería) and HARPS on the 3.6 m telescope. at the La Silla Chile Observatory), as well as photometric assistance from the ASAP and EXORAP surveys. IAC researchers Alejandro Suárez Mascareño and Rafael Rebolo also participate in this work.