Discovery of Exoplanet Orbiting the Closest Single Star to the Sun

Using ESO’s Very Large Telescope, researchers discovered an exoplanet orbiting Barnard’s star, the closest single star to our Sun. Located six light-years away, Barnard’s star is the second-nearest stellar system after Alpha Centauri’s triple-star group. This new exoplanet, Barnard b, has at least half the mass of Venus and completes its orbit in just over three Earth days. The planet is situated twenty times closer to Barnard’s star than Mercury is to the Sun with a surface temperature of around 125 °C.

The discovery, announced in the journal Astronomy & Astrophysics, comes after five years of observing Barnard’s star with ESO’s VLT at Paranal Observatory in Chile. According to Jonay González Hernández of Instituto de Astrofísica de Canarias, lead author of the study, the team was confident they would eventually find something. Despite promising signals detected as far back as 2018, this is the first confirmed exoplanet orbiting Barnard's star.

Astronomers target red dwarfs like Barnard’s star because it is easier to detect low-mass rocky planets around them. Although Barnard b is among the lowest-mass exoplanets known, it is too close to its star to reside within the habitable zone, a region where liquid water could exist. ESPRESSO, a precise instrument that measures the gravitational pull-induced wobble of stars, was key in observing Barnard b. Further confirmation came from instruments like HARPS at La Silla Observatory and CARMENES. New data failed to support the existence of an exoplanet suggested in 2018.

While investigating Barnard’s star, the team also identified indications of three additional exoplanets, although these candidates need further observation to be confirmed. Alejandro Suárez Mascareño of Instituto de Astrofísica de Canarias emphasizes the need for continued observation to verify other signals. He highlights that the discovery of Barnard b, alongside other findings such as Proxima b and d, demonstrates the prevalence of low-mass planets in our cosmic vicinity.

The forthcoming Extremely Large Telescope (ELT) with its ANDES instrument aims to revolutionize exoplanet research. Upon completion, it will enable the detection and atmospheric study of more small, rocky exoplanets in the temperate zones of nearby stars, exceeding the capabilities of currently existing telescopes.

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