Free Astronomy Magazine July-August 2020

9 JULY-AUGUST 2020 EXOPLANETS a second planet in the Proxima Centauri sys- tem. The presence of the new candidate emerged from the processing of data collected by HARPS over 17 years of activity. In these data were dis- covered a “swing effect” of the star, with a decid- edly longer period than that attributable to Proxima b: around 1900 days. From the periodic- ity of the signal and the deviation of the star, Damasso and Del Sordo calculated both the dis- tance of the (possible) second planet from its star, about 1.5 UA, and its minimum mass, close to six Earth masses. It would therefore be a “super- Earth” traveling in an orbit far enough from Proxima Centauri to translate into surface temperatures lower than -200 °C. The first announcement in April 2019 was followed in January of this year by the pub- lication in Science Advances of a paper de- tailing the discovery. In addition to Damasso and Del Sordo, the authorship of this 2020 paper includes the aforementioned Anglada- Escudé and many other researchers. The au- thors are justifiably cautious about the exis- tence of the new planet, called Proxima c, and say that more detailed observations will be needed to confirm it. In fact, there is a re- mote possibility that the signal attributed to the second planet is ac- tually produced by the magnetic activity of the red dwarf. One way to confirm the existence of Proxima c with certainty would be to photograph it di- rectly, a task certainly within the reach of the next generation of tel- escopes. Nonetheless, the results of the first attempt to recognize that planet on archive images produced by the SPHERE instrument, installed on the ESO’s Very Large Telescope (Cerro Paranal, Chile), were already published M ario Damas- so and Fa- bio Del Sordo, at the end of their Breakthrough Dis- cuss session, dur- ing which they reported the pos- sible existence of the planet Proxima c. [Breakthrough Initiatives] The infographic below compares regions of the same size in the Proxima Centauri system and in our Solar System. Proxima b is lo- cated inside the habitable zone, the one where liquid water could exist on its rocky surface. [ESO/ M. Kornmesser/ G. Coleman]