A new planet has been detected orbiting the star closest to the Sun.

A team of astronomers using the VLT of the European Southern Observatory (VLT) in Chile has found evidence of another planet orbiting Proxima Centauri, the closest star to our Solar System. This candidate planet is the third detected in the system and the lightest ever discovered orbiting this star. At only a quarter of the Earth's mass, the planet is also one of the lightest exoplanets ever found.

“The discovery shows that the closest stellar appears to be filled with interesting new worlds, within the reach of further study and future explorations, ”explained João Faria, researcher at the Instituto de Astrofísica e Ciências do Espaço, in Portugal and lead author of the study published today in Astronomy & Astrophysics. Proxima Centauri is the closest star to the Sun, located just over four light-years away.

The newly discovered planet, called Proxima d, orbits Proxima Centauri at a distance of about four million kilometers. , less than one-tenth the distance of Mercury from the Sun. It orbits between the star and the habitable zone, the area around a star where liquid water can exist on a planet's surface, and takes only five days to complete a 'orbit around Proxima Centauri. The star is already known to host two other planets: Proxima b, a planet with a mass comparable to that of the Earth that orbits the star every 11 days and is within the habitable zone, and the candidate Proxima c, which is located on a five-year longer orbit around the star.

Artistic illustration of the new potential exoplanet and its host star. Credits: M. Kornmesser / ESO

Proxima b was discovered a few years ago using the HARPS instrument on ESO's 3.6-meter telescope. The discovery was confirmed in 2020 when scientists observed the Proxima system with a new instrument on ESO's VLT that had higher accuracy, the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO).


With just a quarter of the mass of the Earth, Proxima d is the lightest exoplanet ever measured using the radial velocity technique, passing a recently discovered planet in planetary system L 98-59. The technique works by collecting small oscillations in the movement of a star created by the gravitational attraction of an orbiting planet. The effect of Proxima d's gravity is so small that it causes Proxima Centauri to move back and forth at about 40 centimeters per second (1.44 kilometers per hour).

"This result is extremely important," he said Pedro Figueira, scientist of the ESPRESSO instrument at ESO in Chile. “It shows that the radial velocity technique has the potential to unveil a population of light planets, such as ours, which should be the most abundant in our galaxy and which can potentially hosting life as we know it ”.