Astronomers have found evidence of another planet orbiting Proxima Centauri, the nearest neighbouring star of the Sun.
Proxima d, as the newly discovered exoplanet has been christened, is the third to have been detected in Proxima Centauri's orbit since 2016. Exoplanets are planets lying outside our solar system.
According to a press release by the European Southern Observatory (ESO), the planet’s mass is a quarter of Earth’s, making it one of the lightest exoplanets to have been discovered so far. It orbits Proxima Centauri in nearly five Earth days.
“The effect of Proxima d’s gravity is so small that it only causes Proxima Centauri to move back and forth at around 40 centimetres per second (1.44 kilometres per hour),” the release explains.
Proxima d orbits the star at a distance of about four million kilometres. To put this in context, four million kilometres is less than one-tenth the distance between the Sun and its nearest planet, Mercury.
The discovery has been made using ESPRESSO (Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations), installed on the European Southern Observatory's Very Large Telescope (ESO’s VLT) in Cerro Paranal in northern Chile. The findings of the study were published in peer-reviewed journal Astronomy and Astrophysics.
The newly spotted celestial object is also believed to be orbiting between Proxima Centauri and the ‘habitable zone’, or the area around a star where water could exist in liquid form.
The other two planets orbiting Proxima Centauri - Proxima b and Proxima c - have orbits of 11 Earth days and five Earth years respectively. Proxima b is the first to have been discovered and lies in the habitable zone of the star whereas Proxima c is believed to be too cold to sustain life as humans know it.
The mass of Proxima b is comparable with that of Earth.
Among the three exoplanets, the presence of Proxima b has so far been conclusively established by follow-up observations in 2020.
"The discovery shows that our closest stellar neighbour seems to be packed with interesting new worlds, within reach of further study and future exploration," said João Faria, a researcher at Portugal's Instituto de Astrofísica e Ciências do Espaço, and the lead author of the study.
“This result clearly shows what ESPRESSO is capable of and makes me wonder about what it will be able to find in the future,” Faria added.