A “superearth” type planet named GJ 536 b with a mass around 5.4 the Earth’s mass has been discovered in orbit around a nearby very bright star. The planet was discovered by PhD student Alejandro Suárez Mascareño, of the Instituto de Astrofísica de Canarias (IAC) and the University of La Laguna (ULL), and his thesis directors at the IAC Rafael Rebolo and Jonay Isaí González Hernández.
This exoplanet, which orbits the star GJ 536, is not within the star’s Goldilocks zone, but it does have a short orbital period of 8.7 days. Coupled to the luminosity of its star, a red dwarf which is not very hot and close to our Sun, these factors make it an attractive contender for investigating its atmospheric composition. A cycle of magnetic activity similar to that of the Sun was found during the research. Its period was however shorter at only 3 years.
Mascareño, the first author on the article, notes that although GJ 536 b is the only planet found thus far, they will continue monitoring the star to see if they can find other companions. He adds that rocky planets, especially round stars of this type, are usually found in groups. The team is confident that they can find other low mass planets (other “superearths”) in orbits further away from the star. They expect these will have periods ranging from 100 days up to a few years. To determine this new exoplanet’s radius and mean density, a program of monitoring for transits has been prepared.
Jonay Isaí González notes that although the exoplanet is rocky and orbits a star much smaller and cooler than the Sun, the star is nearby and bright. It can also be seen from both the northern and southern hemispheres. This makes the star very interesting for future high stability spectrographs, as well as for the possible detection of another rocky planet in its habitability zone.
Rafael Rebolo explained that they had to measure the velocity of the star with an accuracy in the order of a meter per second to detect the planet. This accuracy will be improved by a factor of ten with the construction of the new ESPRESSO instrument. The construction of this instrument, co-directed by the IAC, will enable scientist to extend their search to planets with conditions similar to Earth, both around this star, but also around many other nearby stars.
The planet was detected as the result of a joint effort between the Geneva Observatory and the IAC. The teams used the HARPS (High Accuracy Radial velocity Planet Seeker) North, on the Telescopio Nacional Galileo (TNG) at the Roque de los Muchachos Observatory, Garafia (La Palma) and the HARPS spectrograph on the 3.6M ESO Telescope at La Silla (Chile).
This planet was discovered during Alejandro Suárez Mascareño’s preparation of his doctoral thesis, within the program of Training of Research Personnel of the Ministry of Economy, Industry, and Competitivity (MINECO).
Discovery has been outlined more in detail in the journal Astronomy & Astrophysics.