Gliese 687

Gliese 687, or GJ 687 (Gliese–Jahreiß 687) is a red dwarf in the constellation Draco. This is one of the closest stars to the Sun and lies at a distance of 14.84 light-years (4.55 parsecs). Even though it is close by, it has an apparent 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.^[7] Old books and articles refer to it as Argelander Oeltzen 17415.^[9]

Gliese 687

Gliese 687 is the small orange star located in the center of the above image.
Observation data Epoch J2000      Equinox J2000
Constellation	Draco
Right ascension	17h 36m 25.89931s[1]
Declination	+68° 20′ 20.9096″[1]
Apparent magnitude (V)	9.15[2]
Characteristics
Spectral type	M3.5 V[3]
U−B color index	1.06
B−V color index	1.49
Astrometry
Radial velocity (Rv)	−28.90±0.13[1] km/s
Proper motion (μ)	RA: −320.675 mas/yr[1] Dec.: −1269.893 mas/yr[1]
Parallax (π)	219.7898±0.0210 mas[1]
Distance	14.839 ± 0.001 ly (4.5498 ± 0.0004 pc)
Absolute magnitude (MV)	10.87
Details
Mass	0.40±0.02[4] M☉
Radius	0.4183±0.0070[5] R☉
Luminosity	0.02128±0.00023[5] L☉
Surface gravity (log g)	4.66[6] cgs
Temperature	3,413±28[5] K
Metallicity [Fe/H]	+0.11 ± 0.20[6] dex
Rotation	61.8±1.0 d[7]
Rotational velocity (v sin i)	<2.8[8] km/s
Other designations
BD+68 946, GJ 687, HIP 86162, SAO 17568, LHS 450, LTT 15232, PLX 4029.00[2]
Database references
SIMBAD	data
Exoplanet Archive	data
Gliese 687 Location of Gliese 687 in the constellation Draco

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.

It displays no excess of infrared radiation that would indicate orbiting dust.^[10]

Gliese 687 is a solitary red dwarf that emits X-rays.^[11]

Planetary system

In 2014, Gliese 687 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.^[7] Another Neptune-mass planet candidate was discovered in 2020, in a further out and much colder orbit.^[4]

The Gliese 687 planetary system^[4]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	≥17.2±1.0 M🜨	0.163±0.003	38.142±0.007	0.17±0.05	—	—
c	≥16.0±4.1 M🜨	1.165±0.023	727.562±12.198	0.40±0.22	—	—

See also

• List of nearest stars and brown dwarfs
• List of exoplanets discovered in 2014 - Gliese 687 b
• List of exoplanets discovered in 2020 - Gliese 687 c