An article published in the journal “Astronomy & Astrophysics” reports the identification of an exoplanet smaller than Earth orbiting Barnard’s Star. A team of researchers identified the exoplanet designated as Barnard b using the ESPRESSO instrument installed on ESO’s VLT in Chile. This discovery was later confirmed with other specialized exoplanet-hunting instruments: HARPS, HARPS-N, and CARMENES. The researchers also detected other signatures that suggest the presence of three exoplanet candidates, but follow-up investigations are needed to verify their existence.
Barnard’s Star is the closest single star to the Sun, as the Alpha Centauri pair and their companion Proxima form a triple system. About six light-years away from Earth, it was already the subject of searches, and a possible exoplanet around this red dwarf star was already announced in November 2018. Unfortunately, subsequent investigations had not confirmed the existence of that planet and indeed over time, the conclusions indicated that it did not exist at all and that its alleged traces were actually the result of stellar activity.
This time, the researchers who identified the new candidate using the ESPRESSO (Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations) instrument installed on the VLT (Very Large Telescope) conducted various checks using data collected with other instruments used in the search for exoplanets.
The HARPS (High Accuracy Radial velocity Planet Searcher) spectrograph is installed on the La Silla Observatory, another ESO facility. The HARPS-N (High Accuracy Radial velocity Planet Searcher for the Northern hemisphere) spectrograph is installed on the Telescopio Nazionale Galileo in the Canary Islands. CARMENES (Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs) is installed at the Calar Alto Observatory in Spain.
In essence, the researchers put together a lot of independently collected data to confirm the existence of the exoplanet that was designated as Barnard b. The data analysis also took into account the activity of Barnard’s Star precisely to avoid new false positives. The data indicates that the exoplanet identified has a mass that is about half that of Venus and about three times that of Mars.
The data about the orbit of the exoplanet Barnard b indicates that its year lasts about 3.15 Earth days. Barnard’s Star has a mass that is only 16% of the Sun’s, so it’s much cooler than the Sun and its system’s habitable zone is much closer to it than the solar system’s is to the Sun. However, Barnard b is too close to its star to be habitable for life forms similar to the Earth’s with an estimated surface temperature of around 125° Celsius. Because of this and Barnard’s Star’s activity, which occasionally includes powerful flares, the image paints it as a planet similar to Mars.
The researchers also found the signatures of three more potential exoplanets orbiting Barnard’s Star. None of them match the one proposed in 2018, confirming again that this was a misinterpretation of the data. Further investigations are needed to verify the existence of these candidates. After the debunking of the candidate reported in 2018, it’s understandable that researchers want to obtain convincing confirmation before announcing new discoveries.
This is another case where ESO’s Extremely Large Telescope (ELT) currently under construction could come in handy, as its ArmazoNes high Dispersion Echelle Spectrograph (ANDES) is also designed to find exoplanets and even possible traces of life on them. It could provide definitive answers about the Barnard’s Star system if they can’t be found with other instruments before the ELT enters service. For now, there’s confirmation of a small planet in the cosmic neighborhood.
