Proxima b is a planet very similar to ours, orbiting the closest star to the Sun, Proxima Centauri. It is the closest ex-earth to us, being 4.24 light years distant from Earth in the constellation Centaurus (remember that the TRAPPIST system is about 40 light years distant). Its orbital period is 11 days. At the time of its discovery, in 2016, Proxima b appeared as a candidate exoplanet with a mass similar to that of Earth, and within the habitable zone of its star. But it was necessary to continue investigating.
Now, an international team of researchers involving scientists from the Instituto de Astrofísica de Canarias (IAC) and other institutions in Spain, Italy, Portugal and Switzerland has confirmed the presence of the extrasolar planet Proxima b using the ESPRESSO spectrograph, at the Very Large Telescope (VLT) of the European Southern Observatory (ESO) located in Chile.
The confirmation has been possible thanks to radial velocity measurements made with the new ESPRESSO instrument , the most accurate spectrograph built to date. ESPRESSO has obtained measurements of the radial velocity of the star Proxima Centauri with an accuracy of 30 cm / s. This is four times better than the precision obtained with HARPS, the instrument used for detection. Combining this precision with the flux of photons, it opens the door to the discovery of the population of terrestrial planets (even those with masses much less than that of Earth) around stars in the solar neighborhood.
“ESPRESSO has shown that it can do better than any previous spectrograph,” says Alejandro Suárez Mascareño, leader of the work. “A new scenario is opening up. So far we have been restricted to discovering planets with masses several times that of Earth, or bordering on a mass of about one mass of Earth, orbiting cool stars. With ESPRESSO that limitation is gone ”.
“It was an important task to confirm Proxima b”, comments Jonay González Hernández, IAC researcher and co-author of the study. “It is one of the most interesting planets known in the solar neighborhood. Its mass, similar to that of the Earth, the possibility that it could harbor life and its proximity, make it one of the ideal candidates to search for biomarkers using the next generation of telescopes , such as the HIRES spectrograph for the future 39 m ELT. , in whose construction the IAC participates ”.
More planets?
The researchers also found hints of a second signal in the data, the origin of which is still entirely clear. “If it turns out to be the sign of a planet, it could have a mass less than a third of the mass of the Earth,” explains Rafael Rebolo, director of the IAC and co-director of the ESPRESSO project.
Reference: Alejandro Suárez Mascareño, Jonay González Hernández and Rafael Rebolo López, from the IAC researchers have also collaborated in this publication Felipe Murgas, Carlos Allende Prieto, Manuel Amate, Ana Belén Fragoso, Ricardo Génova Santos, Enric Pallé, José Luis Rasilla, Samuel Santana Tschudi and Fabio Tenegi Sanginés. “Revisiting Proxima with ESPRESSO”, Astronomy & Astrophysics, May 25, 2020. https://arxiv.org/abs/2005.12114
