Astronomers have found evidence for a new planet circling Proxima Centauri, the nearest star to the sun.
The alien world is only a quarter of the mass of Earth and orbits extremely close to its parent star, at one tenth of the distance between the sun and Mercury, the solar system’s innermost planet.
Researchers spotted the new planet after studying tiny wobbles in the motion of Proxima Centauri caused by the gravitational pull it exerts as it swings around the star. Observations taken with the European Southern Observatory’s Very Large Telescope (VLT) in Chile suggest the planet completes a full orbit of the star every five days.
The discovery shows that our closest stellar neighbour is “packed with interesting new worlds” within reach of further study and future exploration, said João Faria, a researcher at the Institute of Astrophysics and Space Sciences in Portugal and lead author on the study.
Scientists believe the planet orbits about 2.4m miles (4m km) from Proxima Centauri, meaning it is closer to the star than its habitable zone where the temperature range is just right for water to run freely. Details are published in the journal Astronomy & Astrophysics.
Named Proxima d, the planet is the third – and the lightest – to be spotted around Proxima Centauri, which at four light years away is the closest star to the solar system. It joins Proxima b, a planet with a mass comparable to that of Earth, which completes an orbit every 11 days, and Proxima c, which is believed to take about five years to circle the star.
The first hints of the planet came in 2020 when astronomers were observing Proxima Centauri to confirm the existence of Proxima b. The measurements revealed a weak signal in the star’s motion that had the hallmarks of being caused by a planet orbiting every five days.
Further observations taken with an instrument on ESO’s telescope called Espresso confirmed astronomers’ suspicions that a planet was the cause and not changes in the star itself.
“This is a very low mass planet, and is the third candidate around the star closest to us,” Faria said. “It shows that these planets, similar to the Earth, may be common in our galaxy, and just close by. And it makes us wonder about the possible conditions for habitability in these planet systems and if it’s possible for life to appear in other places in the universe.”
