A new Super-Earth discovered around a nearby star

A team of astronomers announces the discovery of a new exoplanet: a Super-Earth located less than 36 light years from our system. On the other hand, this a priori rocky world does not evolve in the habitable zone of its star.


To detect exoplanets, astronomers generally rely on two methods: transit and radial speed. The first is to measure the curve of light emitted by distant stars. Periodic dips of luminosity are then sometimes observed, testifying to the passage of a planet in front of its star (that is to say in transit) in relation to the observer (the astronomers). The second, that of radial speed, is based on spectral observation of the stars, looking for signs of “flickering”. Concretely, the astronomers will seek to know if the observed star moves away or approaches the Earth, movements which testify to a slight gravitational influence of a planet on the said star.


This technique is not the most prolific in terms of discoveries, but it has nonetheless enabled us to identify more than 600 exoplanets to date out of the more than 4,000 identified . Out of this sample of 600, 116 evolve around red dwarfs . These stars, which are smaller, less luminous and “cooler” than the Sun, are the most common in our galaxy.


A nearby Super-Earth


More recently, a team of astronomers led by Borja Toledo-Padrón, from the Spanish University of La Laguna, discovered a new world around one of these stars. Named GJ 740 b, the new exoplanet is about 36 light years from Earth. It is a Super-Earth at least 2.96 times more massive than our planet . Remember that we call “Super-Earth” an exoplanet with a mass between that of the Earth and that of a giant planet (about ten Earth masses).


Size comparison between the Earth, a super-earth (GJ 1214 b, center) and the giant Neptune. Credit: Aldaron / Wikipedia


From tracking scans, we also know that GJ 740 circles its star every 2.377 days, at a distance of about 0.029 AU . As a reminder, one AU is equivalent to the Earth-Sun distance, or about 150 million kilometers. According to the authors, this distance places the planet outside the habitable zone of its host. The equilibrium temperature of 740 GJ b was calculated at 829 Kelvin is approximately 555 ° C .


Since the radius of GJ 740 b is unknown, it is currently impossible to determine its composition. On the other hand, its mass and its short orbital period suggest that it is a rocky object .


Finally, the data suggests that the system could host a second planet, more massive and more distant. The researchers speculate that this potential world is about a hundred times as massive as Earth and revolves around the mother star in just under ten years.

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