A candidate super-Earth planet orbiting near the snow line of Barnard's star

DOI: 
10.1038/s41586-018-0677-y
Publication date: 
01/11/2018
Main author: 
Ribas, I.
IAA authors: 
Rodríguez-López, C.;Rodríguez, E.;Amado, P. J.;López-González, M. J.;Anglada-Escudé, G.
Authors: 
Ribas, I.;Tuomi, M.;Reiners, A.;Butler, R. P.;Morales, J. C.;Perger, M.;Dreizler, S.;Rodríguez-López, C.;González Hernández, J. I.;Rosich, A.;Feng, F.;Trifonov, T.;Vogt, S. S.;Caballero, J. A.;Hatzes, A.;Herrero, E.;Jeffers, S. V.;Lafarga, M.;Murgas, F.;Nelson, R. P.;Rodríguez, E.;Strachan, J. B. P.;Tal-Or, L.;Teske, J.;Toledo-Padrón, B.;Zechmeister, M.;Quirrenbach, A.;Amado, P. J.;Azzaro, M.;Béjar, V. J. S.;Barnes, J. R.;Berdiñas, Z. M.;Burt, J.;Coleman, G.;Cortés-Contreras, M.;Crane, J.;Engle, S. G.;Guinan, E. F.;Haswell, C. A.;Henning, Th.;Holden, B.;Jenkins, J.;Jones, H. R. A.;Kaminski, A.;Kiraga, M.;Kürster, M.;Lee, M. H.;López-González, M. J.;Montes, D.;Morin, J.;Ofir, A.;Pallé, E.;Rebolo, R.;Reffert, S.;Schweitzer, A.;Seifert, W.;Shectman, S. A.;Staab, D.;Street, R. A.;Suárez Mascareño, A.;Tsapras, Y.;Wang, S. X.;Anglada-Escudé, G.
Journal: 
Nature
Refereed: 
Yes
Publication type: 
Article
Volume: 
563
Pages: 
365-368
Abstract: 
Barnard's star is a red dwarf, and has the largest proper motion (apparent motion across the sky) of all known stars. At a distance of 1.8 parsecs<SUP>1</SUP>, it is the closest single star to the Sun; only the three stars in the α Centauri system are closer. Barnard's star is also among the least magnetically active red dwarfs known<SUP>2,3</SUP> and has an estimated age older than the Solar System. Its properties make it a prime target for planetary searches; various techniques with different sensitivity limits have been used previously, including radial-velocity imaging<SUP>4-6</SUP>, astrometry<SUP>7,8</SUP> and direct imaging<SUP>9</SUP>, but all ultimately led to negative or null results. Here we combine numerous measurements from high-precision radial-velocity instruments, revealing the presence of a low-amplitude periodic signal with a period of 233 days. Independent photometric and spectroscopic monitoring, as well as an analysis of instrumental systematic effects, suggest that this signal is best explained as arising from a planetary companion. The candidate planet around Barnard's star is a cold super-Earth, with a minimum mass of 3.2 times that of Earth, orbiting near its snow line (the minimum distance from the star at which volatile compounds could condense). The combination of all radial-velocity datasets spanning 20 years of measurements additionally reveals a long-term modulation that could arise from a stellar magnetic-activity cycle or from a more distant planetary object. Because of its proximity to the Sun, the candidate planet has a maximum angular separation of 220 milliarcseconds from Barnard's star, making it an excellent target for direct imaging and astrometric observations in the future.
Database: 
ADS
SCOPUS
URL: 
https://ui.adsabs.harvard.edu/#abs/2018Natur.563..365R/abstract
ADS Bibcode: 
2018Natur.563..365R