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Star in the constellation Draco From Wikipedia, the free encyclopedia
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 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 | |
| Database references | |
| SIMBAD | data |
  Gliese 687 Location of Gliese 687 in the constellation Draco | |
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]
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]
| 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 | — | — |
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