New Super-Earth Detected Orbit Red Dwarf Star

In recent years there has been a thorough study of red dwarf stars 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, a doctoral student Severo Ochoa-La Caixa at the Institute of Astrophysics Canary Institute (IAC), specializing in the search for planets around this type of stars, discovered a super-Earth orbit around the star GJ 740, a red dwarf star is 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 object 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 & 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 by the satellite TESS “, 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 (close to 100 Earth masses), although its radio speed signal could be due to the star’s magnetic cycle (similar to that of the Sun), so that 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 by 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 planets orbiting it), discovered a total of 156 new ones. planets around cool stars. According to its data, it has been estimated that this type of star contains 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 planet’s mass and the star’s mass compared to stars in warmer spectral classes (which makes it easier to detect the planets’ signals). like the large number of this kind of stars in our Galaxy, ”comments Borja Toledo Padrón.

Cool stars are also an ideal target for searching for planets by the method of radio speed. This method is based on the detection of small variations in the speed of a star due to the gravitational pull of a planet in orbit around it, by spectroscopic observations. Since the discovery in 1998 of the first radial velocity signal of an exoplanet around a cool star, a total of 116 exoplanets have been discovered around this class of stars by the method of radial velocity. “The main difficulty of this method relates to the intense magnetic activity of such stars, which can produce spectroscopic signals very similar to those due to an exoplanet,” says Jonay I. González Hernández, an IAC researcher who is a co-author of this that article.

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The study is part of the HADES project (HArps 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 Planetary Architecture Systems), whose purpose is the detection and characterization of exoplanets around cool stars in which HARPS-N is used, in 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, complemented by measurements with the spectrograph CARMENES on the 3.5m telescope at the Calar Alto Observatory (Almería) and HARPS, on the 3.6m telescope at the La Silla Chile Observatory. , as well as photometric support of the ASAP and EXORAP surveys. Also participating in this work are IAC researchers Alejandro Suárez Mascareño, and Rafael Rebolo.

Article: B. Toledo-Padrón, A. Suárez Mascareño, JI González Hernández, R. Rebolo, and others. “Super-Earth in close orbit around the M1V star GJ 740”. Astronomy & Astrophysics, April 7, 2021. DOI: 10.1051 / 0004-6361 / 202040099

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