Scientists have confirmed the existence of an Earth-sized planet that orbits the star closest to the sun. The planet is 1.17 times the mass of Earth and is located in the habitable zone of its star, Proxima Centauri, 4.2 light years away.
A team of scientists at the University of Geneva (UNIGE) first detected the new planet, known as Proxima b, four years ago using the High Accuracy Radial Velocity Planet Searcher (HARPS).
For the current study, the researchers had access to data collected by ESPRESSO, a newer generation spectrograph that can detect planets around low-mass stars with unprecedented precision.
ESPRESSO performed radial velocity measurements on Proxima Centauri with an accuracy of 30 centimeters a second. These observations are about three times more precise than those that were obtained four years ago.
“We were already very happy with the performance of HARPS, which has been responsible for discovering hundreds of exoplanets over the last 17 years,” said study co-author Professor Francesco Pepe.
“We’re really pleased that ESPRESSO can produce even better measurements, and it’s gratifying and just reward for the teamwork lasting nearly 10 years.”
The ESPRESSO data showed that the minimum mass of Proxima b is 1.17 earth masses and that it orbits around its star in only 11.2 days.
“Confirming the existence of Proxima b was an important task, and it’s one of the most interesting planets known in the solar neighborhood,” said study lead author Alejandro Suarez Mascareño.
According to the experts, Proxima b is about 20 times closer to its star than the Earth is to the sun but receives a comparable amount of energy.
The planet has a surface temperature that is not too cold and not too hot for liquid water, which means there is potential for Proxima b to harbor life.
However, the researchers said there is still a long way to go before they can speculate that life exists on Proxima b.
For example, Proxima Centauri is an active red dwarf and the planet is showered with 400 times more solar X-rays compared to Earth.
“Is there an atmosphere that protects the planet from these deadly rays? And if this atmosphere exists, does it contain the chemical elements that promote the development of life (oxygen, for example)? How long have these favourable conditions existed?”
“We’re going to tackle all these questions, especially with the help of future instruments like the RISTRETTO spectrometer,” said study co-author Christophe Lovis.
The study is published in the journal Astronomy and Astrophysics.