Discovered a new super-Earth around a red dwarf star

Artist's impression of the super-earth orbiting the red dwarf GJ 740.

Artist's impression of the super-earth orbiting the red dwarf GJ 740.

A team of researchers led by Borja Toledo, PhD student Severo Ochoa-La Caixa at the Instituto de Astrofísica de Canarias (IAC), has discovered a super-Earth around GJ 740, a cold dwarf star located about 36 light years from Earth.

In a statement the IAC points out that in recent years an exhaustive monitoring of red dwarf stars has been carried out with the aim of finding exoplanets orbiting around them and recalls that these stellar bodies possess an effective temperature between 2,400 and 3,700 K (more than 2,000 degrees cooler than the Sun) and a mass between 0.08 and 0.45 solar masses.

The new super-earth discovered orbits its star with an orbital period of 2.4 days and has an approximate mass of 3 land masses.

Due to the closeness of the star to the Sun and the planet to its star, this new super-earth may be the object of study in future research with large-diameter telescopes at the end of this decade, adds the IAC, which states that the results of the study have been published in the journal 'Astronomy & Astrophysics'.

"We are facing the planet with the second shortest orbital period around this type of star. The mass and orbital period of this planet suggest a rocky composition, as well as an estimated radius of 1.4 terrestrial radii, which can be confirmed with future observations of the TESS satellite ”, explains Borja Toledo, main author of the discovery.

The data also indicate the presence of a possible second planet with an orbital period of 9 years and a mass similar to that of Saturn (approximately 100 Earth masses), although its radial velocity signal could be caused by the star's magnetic cycle (similar to that experienced by the Sun), and therefore more data is necessary to confirm the origin of this signal.

The IAC explains that the Kepler mission, recognized for being one of the most successful in detecting exoplanets through the transit method (which consists of the search for small periodic variations in the brightness of the star caused by transits of the planets orbiting them), has discovered a total of 156 new planets around cool stars.

From these data it has been estimated that this type of stars host an average of 2.5 planets with an orbital period less than 200 days.

"The search for new exoplanets around cool stars is driven by the smaller difference between planetary mass and stellar mass compared to stars of other spectral classes (which facilitates the detection of planetary signals), as well as the great abundance of this type of stars in our galaxy ”, comments Borja Toledo.

Cool stars are also an ideal target for searching for planets via the radial velocity method.

This method is based on the detection of small variations in speed due to gravitational attraction exerted by planets orbiting around them, through spectroscopic observations.

From the discovery in 1998 of the first radial velocity signal of an exoplanet around a cold star to date a total of 116 exoplanets around this class of stars using the radial velocity technique.

"The greatest intrinsic 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 caused by an exoplanet", declares Jonay I. González Hernández, IAC researcher and co-author of this work.

The study is part of the HADES (HArps-n red Dwarf Exoplanet Survey) project, in which the IAC, the Institut de Ciències de l'Espai (IEEC-CSIC) of Catalonia, and the Italian GAPS (Global Architecture of Planetary) program collaborate. Systems), and whose objective is the detection and characterization of exoplanets around cold stars.

For this, the HARPS-N spectrograph is used, located at the Telescopio Nazionale Galileo (TNG) of the Roque de Los Muchachos Observatory (Garafía, La Palma).

This detection has been possible thanks to a six-year observation campaign with HARPS-N, complemented with measurements from the CARMENES (located at the Calar Alto Observatory, Almería) and HARPS (located at the La Silla Observatory, Chile) spectrographs, as well as the photometric support provided by the ASAS and EXORAP surveys.

IAC researchers Alejandro Suárez and Rafael Rebolo also participate in this work.


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