Gliese 86
Binary star system in the constellation Eridanus
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Gliese 86 (13 G. Eridani, HD 13445) is a K-type main-sequence star 35 light-years away in the constellation of Eridanus. It has been confirmed that a white dwarf orbits the primary star. In 1998 the European Southern Observatory announced that an extrasolar planet was also orbiting the star.[18]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Eridanus[1] |
| Gliese 86 A | |
| Right ascension | 02h 10m 25.9182s[2] |
| Declination | −50° 49′ 25.465″[2] |
| Apparent magnitude (V) | 6.17[3] |
| Gliese 86 B | |
| Right ascension | 02h 10m 26.1144s[4] |
| Declination | −50° 49′ 26.334″[4] |
| Apparent magnitude (V) | 14.0[5] |
| Characteristics | |
| A | |
| Evolutionary stage | main sequence[2] |
| Spectral type | K1V[6] |
| U−B color index | 0.44[7] |
| B−V color index | 0.82[7] |
| B | |
| Evolutionary stage | white dwarf[8] |
| Spectral type | DQ6[9][10] |
| Astrometry | |
| A | |
| Radial velocity (Rv) | +55.22±0.15[2] km/s |
| Proper motion (μ) | RA: +2,125.416 mas/yr[2] Dec.: +637.975 mas/yr[2] |
| Parallax (π) | 92.9251±0.0461 mas[2] |
| Distance | 35.10 ± 0.02 ly (10.761 ± 0.005 pc) |
| Absolute magnitude (MV) | 5.95[11] |
| Orbit[9] | |
| Primary | Gliese 86 A |
| Name | Gliese 86 B |
| Period (P) | ≈100 yr |
| Semi-major axis (a) | 23.7 au |
| Eccentricity (e) | 0.429 |
| Inclination (i) | 126.44° |
| Longitude of the node (Ω) | 234.2° |
| Details | |
| Gliese 86 A | |
| Mass | 0.83±0.05[12] M☉ |
| Radius | 0.79±0.03[12] R☉ |
| Luminosity | 0.41[13] L☉ |
| Surface gravity (log g) | 4.56±0.10[12] cgs |
| Temperature | 5,180±80[12] K |
| Metallicity [Fe/H] | −0.27±0.07[12] dex |
| Rotation | 30.0 days[14] |
| Rotational velocity (v sin i) | 2.0±1.0[12] km/s |
| Age | 10±1[12] Gyr |
| Gliese 86 B | |
| Mass | 0.5425[9] M☉ |
| Surface gravity (log g) | 8.00[15] cgs |
| Temperature | 5,000±500[8] K |
| Other designations | |
| GJ 86, WDS J02104-5049 | |
| Gliese 86A: CD−51°532, HD 13445, HIP 10138, HR 637, SAO 232658[16] | |
| Gliese 86B: WD 0208-510[17] | |
| Database references | |
| SIMBAD | data |
| B | |
| Exoplanet Archive | data |
| ARICNS | data |
Stellar components
The primary companion (Gliese 86 A) is a K-type main-sequence star of spectral type K1V. The characteristics in comparison to the Sun are 83% the mass, 79% the radius, and 50% the luminosity. The star has a close-orbiting massive Jovian planet.
Gliese 86 B is a white dwarf located around 21 AU from the primary star, making the Gliese 86 system one of the tightest binaries known to host an extrasolar planet.[19] It was discovered in 2001 and initially suspected to be a brown dwarf,[20] but high contrast observations in 2005 suggested that the object is probably a white dwarf, as its spectrum does not exhibit molecular absorption features which are typical of brown dwarfs.[8] Assuming the white dwarf has a mass about half that of the Sun and that the linear trend observed in radial velocity measurements is due to Gliese 86 B, a plausible orbit for this star around Gliese 86 A has a semimajor axis of 18.42 AU and an eccentricity of 0.3974.[21] When both stars were on the main sequence, the separation between the two stars was closer, at around 9 AU.[9] More precise measurements for the white dwarf give it a mass of 55% the mass of the Sun[9] and a temperature of around 8200 K.[12]
Planetary system
The planet Gliese 86 b was discovered by the Swiss 1.2 m Leonhard Euler Telescope operated by the Geneva Observatory.[22] Such an object was formed from a protoplanetary disk that was truncated at 2 AU from the parent star.[9]
The radial velocity measurements of Gliese 86 show a linear trend once the motion due to this planet are taken out. This may be associated with the orbital motion of the white dwarf companion.
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥6.588±0.018 MJ | 0.114340±0.000001 | 15.76480±0.00004 | 0.048±0.002 | — | — |
See also
- List of exoplanets discovered before 2000 - Gliese 86b