1. A candidate super-Earth planet orbiting near the snow line of Barnard’s star
- Author
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Ribas, I, Tuomi, M, Reiners, A, Butler, RP, Morales, JC, Perger, M, Dreizler, S, Rodríguez-López, C, González Hernández, JI, Rosich, A, Feng, F, Trifonov, T, Vogt, SS, Caballero, JA, Hatzes, A, Herrero, E, Jeffers, SV, Lafarga, M, Murgas, F, Nelson, RP, Rodríguez, E, Strachan, JBP, Tal-Or, L, Teske, J, Toledo-Padrón, B, Zechmeister, M, Quirrenbach, A, Amado, PJ, Azzaro, M, Béjar, VJS, Barnes, JR, Berdiñas, ZM, Burt, J, Coleman, G, Cortés-Contreras, M, Crane, J, Engle, SG, Guinan, EF, Haswell, CA, Henning, Th, Holden, B, Jenkins, J, Jones, HRA, Kaminski, A, Kiraga, M, Kürster, M, Lee, MH, López-González, MJ, Montes, D, Morin, J, Ofir, A, Pallé, E, Rebolo, R, Reffert, S, Schweitzer, A, Seifert, W, Shectman, SA, Staab, D, Street, RA, Suárez Mascareño, A, Tsapras, Y, Wang, SX, and Anglada-Escudé, G
- Subjects
Space Sciences ,Astronomical Sciences ,Physical Sciences ,General Science & Technology - 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 parsecs1, 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 known2,3 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 imaging4-6, astrometry7,8 and direct imaging9, 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.
- Published
- 2018