학술논문
A candidate super-Earth planet orbiting near the snow line of Barnard’s star
Document Type
article
Author
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; Anglada-Escudé, G
Source
Nature. 563(7731)
Subject
Language
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.