Free Astronomy Magazine May-June 2022

12 MAY-JUNE 2022 ASTRO PUBLISHING Proxima Centauri at a distance of about four million kilometres, less than a tenth of Mercury’s distance from the Sun. It orbits between the star and the habitable zone — the area around a star where liquid water can exist at the surface of a planet — and takes just five days to complete one 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 Earth that orbits the star every 11 days and is within the hab- itable zone, and candidate Proxima c, which is on a longer five-year orbit around the star. Proxima b was discovered a few years ago using the HARPS instru- ment on ESO’s 3.6-metre telescope. The discovery was confirmed in 2020 when scientists observed the Proxima system with a new instru- ment on ESO’s VLT that had greater precision, the Echelle SPectrograph for Rocky Exoplanets and Stable A team of astronomers using the European Southern Ob- servatory’s Very Large Tele- scope (ESO’s VLT) in Chile have found evidence of another planet orbiting Proxima Centauri, the clos- est star to our Solar System. This candidate planet is the third de- tected in the system and the light- est yet discovered orbiting this star. At just a quarter of Earth’s mass, the planet is also one of the lightest ex- oplanets ever found. “The discovery shows that our clos- est stellar neighbour seems to be packed with interesting new worlds, within reach of further study and future exploration,” ex- plains João Faria, a researcher at the Instituto de Astrofísica e Ciên- cias do Espaço, Portugal and lead author of the study published in As- tronomy & Astrophysics . Proxima Centauri is the closest star to the Sun, lying just over four light- years away. The newly discovered planet, named Proxima d, orbits New planet discovered around Proxima Centauri by ESO - Bárbara Ferreira T his artist’s impression shows Proxima d, a planet candidate re- cently found orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The planet is believed to be rocky and to have a mass about a quarter that of Earth. Two other planets known to orbit Proxima Centauri are visible in the image too: Proxima b, a planet with about the same mass as Earth that orbits the star every 11 days and is within the habitable zone, and can- didate Proxima c, which is on a longer five-year orbit around the star. [ESO/L. Calçada]