Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Aries |
Right ascension | 02h 15m 42.77662s [1] |
Declination | +25° 02′ 34.9627″ [1] |
Apparent magnitude (V) | 5.57 [2] (6.40/6.48) [3] |
Characteristics | |
Spectral type | F6 V [4] |
U−B color index | +0.00 [5] |
B−V color index | +0.50 [5] |
Astrometry | |
Radial velocity (Rv) | −44.3 km/s |
Proper motion (μ) |
RA: −89.72
[1]
mas/
yr Dec.: −86.42 [1] mas/ yr |
Parallax (π) | 19.58 ± 0.61 mas [1] |
Distance | 167 ± 5
ly (51 ± 2 pc) |
Absolute magnitude (MV) | 2.03 [2] |
Orbit [6] | |
Period (P) | 23.70 ± 0.12 yr |
Semi-major axis (a) | 0.2353 ± 0.0011″ |
Eccentricity (e) | 0.6816 ± 0.0037 |
Inclination (i) | 104.52 ± 0.16° |
Longitude of the node (Ω) | 236.44 ± 0.22° |
Periastron epoch (T) | 1986.192 ± 0.012 |
Argument of periastron (ω) (secondary) | 84.16 ± 0.16° |
Details | |
21 Ari A | |
Mass | 1.338 ± 0.032 [7] M☉ |
Surface gravity (log g) | 4.12 [8] cgs |
Temperature | 6,299 [8] K |
Metallicity [Fe/H] | +0.02 [8] dex |
Rotational velocity (v sin i) | 12.6 [9] km/s |
Age | 2.2 [2] Gyr |
21 Ari B | |
Mass | 1.374 ± 0.027 [7] M☉ |
Other designations | |
Database references | |
SIMBAD | data |
21 Arietis (abbreviated 21 Ari) is a binary star [3] system in the northern constellation of Aries. 21 Arietis is the Flamsteed designation. It has a combined apparent visual magnitude is 5.57; [2] the brighter member is magnitude 6.40 while the fainter star is magnitude 6.48. [3] The distance to this star system, based upon an annual parallax shift of 19.58 mas, [1] is 167 light-years (51 parsecs). The pair orbit each other with a period of 23.70 years and an eccentricity of 0.68. [3]
The system was initially thought to be a triple system in 1981, since the orbit of the system predicted a mass greater than would be expected from its F6V spectral type. [10] This was later rejected because the distance to the system was overestimated. However, while observing the spectrum of the system, it was found that a giant planet may be causing radial velocity variations. The purported planet would have a mass of 1.40 ± 0.36 MJ, an orbital period of 925 days and orbit the primary star. [7]
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Aries |
Right ascension | 02h 15m 42.77662s [1] |
Declination | +25° 02′ 34.9627″ [1] |
Apparent magnitude (V) | 5.57 [2] (6.40/6.48) [3] |
Characteristics | |
Spectral type | F6 V [4] |
U−B color index | +0.00 [5] |
B−V color index | +0.50 [5] |
Astrometry | |
Radial velocity (Rv) | −44.3 km/s |
Proper motion (μ) |
RA: −89.72
[1]
mas/
yr Dec.: −86.42 [1] mas/ yr |
Parallax (π) | 19.58 ± 0.61 mas [1] |
Distance | 167 ± 5
ly (51 ± 2 pc) |
Absolute magnitude (MV) | 2.03 [2] |
Orbit [6] | |
Period (P) | 23.70 ± 0.12 yr |
Semi-major axis (a) | 0.2353 ± 0.0011″ |
Eccentricity (e) | 0.6816 ± 0.0037 |
Inclination (i) | 104.52 ± 0.16° |
Longitude of the node (Ω) | 236.44 ± 0.22° |
Periastron epoch (T) | 1986.192 ± 0.012 |
Argument of periastron (ω) (secondary) | 84.16 ± 0.16° |
Details | |
21 Ari A | |
Mass | 1.338 ± 0.032 [7] M☉ |
Surface gravity (log g) | 4.12 [8] cgs |
Temperature | 6,299 [8] K |
Metallicity [Fe/H] | +0.02 [8] dex |
Rotational velocity (v sin i) | 12.6 [9] km/s |
Age | 2.2 [2] Gyr |
21 Ari B | |
Mass | 1.374 ± 0.027 [7] M☉ |
Other designations | |
Database references | |
SIMBAD | data |
21 Arietis (abbreviated 21 Ari) is a binary star [3] system in the northern constellation of Aries. 21 Arietis is the Flamsteed designation. It has a combined apparent visual magnitude is 5.57; [2] the brighter member is magnitude 6.40 while the fainter star is magnitude 6.48. [3] The distance to this star system, based upon an annual parallax shift of 19.58 mas, [1] is 167 light-years (51 parsecs). The pair orbit each other with a period of 23.70 years and an eccentricity of 0.68. [3]
The system was initially thought to be a triple system in 1981, since the orbit of the system predicted a mass greater than would be expected from its F6V spectral type. [10] This was later rejected because the distance to the system was overestimated. However, while observing the spectrum of the system, it was found that a giant planet may be causing radial velocity variations. The purported planet would have a mass of 1.40 ± 0.36 MJ, an orbital period of 925 days and orbit the primary star. [7]