Artist’s impression of the super Earth orbiting the red dwarf star GJ-740. Credit: Gabriel Pérez Díaz, SMM (IAC)
In recent years, an extensive study of red dwarf stars has been done 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 times the solar masses. In this context, a team of researchers led by Borja Toledo Padrón, a Severo Ochoa-La Caixa doctoral student at the Instituto de Astrofísica de Canarias (IAC), specializing in the search for planets around this type of stars, has created a super Earth orbits star GJ 740, a red dwarf star about 36 light-years from Earth.
The planet orbits its star for a period of 2.4 days and has a mass about 3 times 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. The mass and period suggest a rocky planet with a radius of about 1.4 Earth radii, which in future observations with the TESS satellite, ”explains Borja Toledo Padrón, the article’s lead author. The data also indicates the presence of a second planet with an orbital period of 9 years, and a mass similar to that of Saturn (nearly 100 Earth masses), although the 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 really due to a planet .
Recognized as one of the most successful in detecting exoplanets using the transit method (looking for small variations in a star’s brightness caused by the passage between it and ourselves of planets revolving around it), the Kepler mission has a total of 156 new planets around cool stars. Based on the data, it is estimated that this type of star hosts an average of 2.5 planets with an orbital period of less than 200 days. The search for new exoplanets around cool 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 facilitates the detection of the planets’ signals), as well as the large number of them. type of star in our Milky Way ”, says Borja Toledo Padrón.
Cool stars are also ideal targets for planetary search using the radial speed method. This method is based on the detection of small variations in the speed of a star due to the gravitational pull 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 cool star, a total of 116 exoplanets have been discovered around this class of stars using the radial velocity method so far. “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,” said Jonay I. González Hernández, an IAC researcher who is a co-author. of this article.
Reference: “A super-Earth in close orbit around the M1V star GJ 740: A collaboration between 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 cooperates with the Institute of Space Sciences (IEEC-CSIC) of Catalonia, and the Italian GAPS program (Global Architecture of Planetary Systems), whose purpose is the detection and characterization of exoplanets around cool stars, which are used HARPS-N, on 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, supplemented by measurements with the CARMENES spectrograph on the 3.5m telescope of the Calar Alto Observatory (Almería) and HARPS, on the 3.6m telescope of the La Silla Observatory (Chile), as well as photometric support for the ASAP and EXORAP surveys. IAC researchers Alejandro Suárez Mascareño and Rafael Rebolo are also participating in this work.