Two Earth-sized planets discovered in the nearby Teegarden’s Star system


An article being published in the journal “Astronomy & Astrophysics” reports the discovery of two planets with a mass close to that of the Earth around Teegarden’s Star, a tiny star about 12.5 light years from Earth and therefore one of the closest. A team of researchers led by the German University of Göttingen used the CARMENES instrument mounted on the Spanish 3.6-meter telescope of the Calar Alto Observatory, Spain, to conduct one of the recent research focused on small stars.

Teegarden’s Star was only discovered in 2003, by a team led by Bonnard J. Teegarden, because it’s really dim. Classified as a red dwarf, its exact nature is still under discussion because according to an estimate reported in an article published in the journal “The Astronomical Journa” in February 2015 its mass is only 8% of the Sun’s, on the border between stars and the substellar objects known as brown dwarfs. It seems to be an ultra-cool dwarf like TRAPPIST-1, which became famous after the confirmation that it has a system with 7 rocky planets.

In Teegarden’s Star’s case, the two spectrographs of the CARMENES (Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs) instrument made it possible to exploit the radial velocity method to discover two planets around it that have masses very similar to the Earth’s. The image (Courtesy University of Göttingen, Institute for Astrophysics. All rights reserved) shows a representation of that system with its two planets, indicated as b and c, and the solar system in the background, magnified in the inset.

The two planets of Teegarden’s Star orbit it in 4.9 and 11.4 Earth days and this means that they’re very close to it but due to the limited amount of energy they receive they could be in ​​their system’s habitable zone. For this reason, Mathias Zechmeister of the Institute of Astrophysics at the University of Göttingen, lead author of the research, stated that the two planets resemble the inner ones of the solar system. Luigi Mancini of the University of Rome Tor Vergata and associate of the Italian National Institute of Astrophysics, another author of the research, explained that the planet indicated as b have characteristics that put it in the first place in the list of potentially habitable planets.

In other cases, exoplanets have been discovered using the transit method by examining the tiny drop in brightness that occurs when they pass in front of their star. This is not the case with Teegarden’s Star, at least for the moment, therefore it’s not possible to know if the two planets identified have an atmosphere and in a positive case if it’s of a type that can ensure the presence of liquid water on their surface and therefore conditions favorable to the development of life forms similar to the Earth’s. The curious thing is that from that system it’s possible to identify the solar system’s planets through the transit method so if there were someone with adequate technologies they could know about the Earth’s existence.

There’s the possibility that there are other planets as well orbiting Teegarden’s Star. It took years of observations to confirm the 7 planets of TRAPPIST-1 with the transit method, searching for them with the radial velocity method is more complex but finding them would confirm that even for these tiny stars it’s normal to have various planets. A big problem is that they emit powerful flares despite their reduced mass so the risk is that their rocky planets are sterilized but after a few billion years they stabilize, leaving more hope of finding planets on which life forms similar to the Earth’s can be born. Red and ultra-cool dwarf stars are the most abundant, the reason why various researches are focusing on them and surely there will be more discoveries.

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