Gliese 687, or GJ 687 (
Gliese–Jahreiß 687) is a
red dwarf in the
constellationDraco. This is one of the
closest stars to the
Sun and lies at an approximate distance of less than 15
light years. Even though it is close by, it has a
magnitude of about 9, so it can only be seen through a moderately sized
telescope. Gliese 687 has a high
proper motion, advancing 1.304
arcseconds per year across the sky. It has a net relative velocity of about 39 km/s.[2] It is known to have a Neptune-mass planet.[8] Old books and articles refer to it as Argelander Oeltzen 17415.[10]
Properties
Gliese 687 has about 40% of the
Sun's mass and nearly 50% of the
Sun's radius. Compared to the
Sun, it has a slightly higher proportion of elements with higher atomic numbers than
helium.[6] It seems to rotate every 60 days and exhibit some chromospheric activity.
In 2014, it was discovered to have a planet,
Gliese 687 b, with a minimum mass of 18.394
Earth masses (which makes it comparable to Neptune), an
orbital period of 38.14 days, a low
orbital eccentricity and inside the habitable zone.[8] Another Neptune mass planet candidate was discovered in 2020, in a further out and much colder orbit.[12]
^Endl, Michael; Cochran, William D.; Kürster, Martin; Paulson, Diane B.; Wittenmyer, Robert A.; MacQueen, Phillip J.; Tull, Robert G. (September 2006). "Exploring the Frequency of Close-in Jovian Planets around M Dwarfs". The Astrophysical Journal. 649 (1): 436–443.
arXiv:astro-ph/0606121.
Bibcode:
2006ApJ...649..436E.
doi:
10.1086/506465.
S2CID14461746.
^Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Alan Henry Batten; John Frederick Heard (eds.). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto:
Academic Press.
Bibcode:
1967IAUS...30...57E.