They discover a planet orbiting the closest individual star to our Sun

Using the VLT (Very Large Telescope) of the European Southern Observatory (ESO), a team has discovered a planet orbiting Barnard’s Star. This is the closest star system to our Sun among all those made up of a single star. Among those made up of more than one, the closest is Alfa Centauri. The distance separating Barnard’s Star from the Sun is greater than that separating it from Alpha Centauri.

On this newly discovered Barnard’s Star planet, a year (or how long it takes to make a complete revolution around its star) lasts just over three Earth days. That exoplanet (a planet outside our solar system) has at least half the mass of Venus.

The team’s observations also indicate the possible existence of three other exoplanet candidates in various orbits around the star.

Located just six light-years away, Barnard’s Star is the second closest star system, after the Alpha Centauri group of three stars. Due to its proximity, it is a prime target in the search for Earth-like exoplanets. Despite a promising detection in 2018, no planets have been confirmed orbiting Barnard’s Star until now.

The discovery of this new exoplanet is the result of observations made over the last five years with the ESO VLT, located at the Paranal Observatory, in Chile. “Although it took us a long time, we were always sure that we could find something,” says Jonay González Hernández, researcher at the Institute of Astrophysics of the Canary Islands (Spain) and lead author of the study. The team was looking for signs of possible exoplanets within the habitable or temperate zone around Barnard’s star, that is, the orbital band where the range of temperatures can allow the existence of liquid water on the surface of a planet. The astronomical community often focuses on the study of red dwarfs (such as Barnard’s Star) because low-mass rocky planets are easier to detect in their surroundings, something more complex to do if they are larger stars. , similar to the Sun.

The astronomical community prefers to look for planets around cool stars, such as red dwarfs, because their temperate orbital zone is much closer to the star than that of hotter stars, such as the Sun. This means that planets orbiting within Their temperate zone have shorter orbital periods, allowing them to be properly monitored over a period of several days or weeks, rather than years. Additionally, red dwarfs are much less massive than the Sun, so they are more easily disturbed by the gravitational pull of surrounding planets and therefore wobble more strongly, making it easier to detect such planets. .

Barnard b, as the newly discovered exoplanet is called, is twenty times closer to Barnard’s star than Mercury is to the Sun. It orbits its star in 3.15 Earth days. Although its surface temperature (125 degrees Celsius) is not infernally hot like that of other planets that take a few days to make a complete revolution around their star, it prevents the existence of liquid water on the surface.

Artist’s recreation of Barnard b, the subterrestrial mass planet that has been discovered orbiting Barnard’s star. (Image: ESO / M. Kornmesser. CC BY 4.0)

Barnard b is one of the lowest-mass exoplanets known and one of the few known with a mass less than Earth.

For their observations, the team used ESPRESSO, a high-precision instrument designed to measure the wobble of a star caused by the gravitational pull of one or more orbiting planets. The results obtained from these observations were confirmed by data from other instruments, also specialized in the search for exoplanets: HARPS, at ESO’s La Silla Observatory, HARPS-N and CARMENES. However, the new data does not support the existence of the exoplanet reported in 2018.

In addition to the confirmed planet, the international team also found indications of the presence of three other exoplanet candidates orbiting the same star. However, these candidates will require additional observations with ESPRESSO to be confirmed. “Now we have to continue observing this star to confirm the other signals of possible candidates,” explains Alejandro Suárez Mascareño, also a researcher at the Institute of Astrophysics of the Canary Islands and co-author of the study. “But the discovery of this planet, along with other previous discoveries like Proxima b and d, shows that our cosmic backyard is full of low-mass planets.”

ESO’s ELT (Extremely Large Telescope), currently under construction, is set to transform the field of exoplanet research. The ELT’s ANDES instrument will allow the scientific community to detect more of these small rocky planets in the temperate zone around nearby stars, beyond the reach of current telescopes, and will allow them to study the composition of their atmospheres.

Jonay González Hernández and his colleagues present the technical details of the Barnard b discovery in the academic journal Astronomy & Astrophysics, under the title “A sub-Earth-mass planet orbiting Barnard’s star.” (Source: ESO. CC BY 4.0)