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The second nearest exoplanet – Proxima c

It is exciting to see that the nearest star to our Sun has more than one planet (Proxima b, [1]). In a paper led by Mario Damasso and Fabio Del Sordo [2] revealed the existence of another one. The Proxima c is a planet with an orbital period of about 1900 days (~5.21 years), a semi-major axis ac = 1.48 ± 0.08 AU, minimum mass (mc sin ic) = 5.8 ± 1.9 M⊕, and equilibrium temperature Teq=39(+16/−18) K. This super-Earth is found further away than the typical distances for this type of planets, something that poses interesting questions with respect to the planet formation and evolution.

Apart from the very interesting results of this paper what is equally exciting is the fact the Fabio has been my office mate since 2017 at the University of Crete. I  am really happy for him and his success. And, as he moved to a new position in Italy, I wish him all the best and new discoveries.

 

Abstract
Our nearest neighbor, Proxima Centauri, hosts a temperate terrestrial planet. We detected in radial velocities evidence of a possible second planet with minimum mass mc sin ic = 5.8 ± 1.9M and orbital period Pc=5.21+0.260.22 years. The analysis of photometric data and spectro-scopic activity diagnostics does not explain the signal in terms of a stellar activity cycle, but follow-up is required in the coming years for confirming its planetary origin. We show that the existence of the planet can be ascertained, and its true mass can be determined with high accuracy, by combining Gaia astrometry and radial velocities. Proxima c could become a prime target for follow-up and characterization with next-generation direct imaging instrumentation due to the large maximum angular separation of ~1 arc second from the parent star. The candidate planet represents a challenge for the models of super-Earth formation and evolution.

 

References:

[1] Anglada-Escudé et al. 2016, “A terrestrial planet candidate in a temperate orbit around Proxima Centauri“, Nature, 536, 437 | NASA/ADS

[2] Mario Damasso, Fabio Del Sordo, Guillem Anglada-Escudé, Paolo Giacobbe, Alessandro Sozzetti, Alessandro Morbidelli, Grzegorz Pojmanski, Domenico Barbato, R. Paul Butler, Hugh R. A. Jones, Franz-Josef Hambsch, James S. Jenkins, María José López-González, Nicolás Morales, Pablo A. Peña Rojas, Cristina Rodríguez-López, Eloy Rodríguez, Pedro J. Amado, Guillem Anglada, Fabo Feng and Jose F. Gómez, 2020, “A low-mass planet candidate orbiting Proxima Centauri at a distance of 1.5 AU”, Science Advances, Vol. 6, no. 3, eaax7467 | NASA/ADS