Observation data Epoch J2000.0 Equinox J2000.0 ( ICRS) | |
---|---|
Constellation | Hydra |
Right ascension | 09h 29m 08.89655s [1] |
Declination | −02° 46′ 08.2649″ [1] |
Apparent magnitude (V) | +4.59 (4.60 + 7.15) [2] |
Characteristics | |
Spectral type | F6 V + ? + K0 [3] |
B−V color index | +0.411±0.015 [2] |
Astrometry | |
Radial velocity (Rv) | +10.85±0.28 [4] km/s |
Absolute magnitude (MV) | +3.28 [5] |
τ1 Hydrae A | |
Proper motion (μ) |
RA: +107.115
[6]
mas/
yr Dec.: −29.652 [6] mas/ yr |
Parallax (π) | 56.2938 ± 0.5309 mas [6] |
Distance | 57.9 ± 0.5
ly (17.8 ± 0.2 pc) |
τ1 Hydrae B | |
Proper motion (μ) |
RA: +138.487
[7]
mas/
yr Dec.: −17.371 [7] mas/ yr |
Parallax (π) | 55.3675 ± 0.0638 mas [7] |
Distance | 58.91 ± 0.07
ly (18.06 ± 0.02 pc) |
Orbit [8] | |
Period (P) | 2,807±23 d |
Eccentricity (e) | 0.33±0.12 |
Periastron epoch (T) | 2445260 ± 150 JD |
Semi-amplitude (K1) (primary) | 2.98±0.39 km/s |
Details | |
τ1 Hydrae A | |
Mass | 1.20 [9] M☉ |
Radius | 1.4 [10] R☉ |
Luminosity (bolometric) | 3.369 [2] L☉ |
Surface gravity (log g) | 4.12±0.14 [9] cgs |
Temperature | 6,473±220 [9] K |
Metallicity [Fe/H] | −0.01 [2] dex |
Rotational velocity (v sin i) | 30.4±1.5 [5] km/s |
Age | 3.61 [2] Gyr |
τ1 Hydrae B | |
Mass | 0.86 [11] M☉ |
Radius | 0.81 [10] R☉ |
Luminosity | 0.435 [7] L☉ |
Temperature | 5,197 [7] K |
Other designations | |
Database references | |
SIMBAD | τ1 Hya AB |
τ1 Hya A | |
τ1 Hya B |
Tau1 Hydrae is a triple star [3] system in the equatorial constellation of Hydra. Based upon the annual parallax shift of the two visible components as seen from Earth, [1] they are located about 18 parsecs (59 ly) from the Sun. The system has a combined apparent visual magnitude of +4.59, [2] which is bright enough to be visible to the naked eye at night.
The inner pair of stars form a single-lined spectroscopic binary with an orbital period of about 2,807 days and an eccentricity of 0.33. [8] The visible member of the pair, component A, is a visual magnitude 4.60 [2] F-type main sequence star with a stellar classification of F6 V. [3] During the 1990s, it was thought to be a Gamma Doradus variable, but this was later discounted as it shows no short-term photometric variability. The star does show some long-term variability, possibly as a result of a magnetic activity cycle similar to the solar cycle. [13]
The tertiary member, component B, is a visual magnitude 7.15 [2] K-type star with a class of K0. [3] It lies at a separation of 1,120 AU from the primary. [14] As of 2012, it was positioned at an angular separation of 67.5 arc seconds along a position angle of 4°. [15]
{{
cite web}}
: CS1 maint: postscript (
link)
Observation data Epoch J2000.0 Equinox J2000.0 ( ICRS) | |
---|---|
Constellation | Hydra |
Right ascension | 09h 29m 08.89655s [1] |
Declination | −02° 46′ 08.2649″ [1] |
Apparent magnitude (V) | +4.59 (4.60 + 7.15) [2] |
Characteristics | |
Spectral type | F6 V + ? + K0 [3] |
B−V color index | +0.411±0.015 [2] |
Astrometry | |
Radial velocity (Rv) | +10.85±0.28 [4] km/s |
Absolute magnitude (MV) | +3.28 [5] |
τ1 Hydrae A | |
Proper motion (μ) |
RA: +107.115
[6]
mas/
yr Dec.: −29.652 [6] mas/ yr |
Parallax (π) | 56.2938 ± 0.5309 mas [6] |
Distance | 57.9 ± 0.5
ly (17.8 ± 0.2 pc) |
τ1 Hydrae B | |
Proper motion (μ) |
RA: +138.487
[7]
mas/
yr Dec.: −17.371 [7] mas/ yr |
Parallax (π) | 55.3675 ± 0.0638 mas [7] |
Distance | 58.91 ± 0.07
ly (18.06 ± 0.02 pc) |
Orbit [8] | |
Period (P) | 2,807±23 d |
Eccentricity (e) | 0.33±0.12 |
Periastron epoch (T) | 2445260 ± 150 JD |
Semi-amplitude (K1) (primary) | 2.98±0.39 km/s |
Details | |
τ1 Hydrae A | |
Mass | 1.20 [9] M☉ |
Radius | 1.4 [10] R☉ |
Luminosity (bolometric) | 3.369 [2] L☉ |
Surface gravity (log g) | 4.12±0.14 [9] cgs |
Temperature | 6,473±220 [9] K |
Metallicity [Fe/H] | −0.01 [2] dex |
Rotational velocity (v sin i) | 30.4±1.5 [5] km/s |
Age | 3.61 [2] Gyr |
τ1 Hydrae B | |
Mass | 0.86 [11] M☉ |
Radius | 0.81 [10] R☉ |
Luminosity | 0.435 [7] L☉ |
Temperature | 5,197 [7] K |
Other designations | |
Database references | |
SIMBAD | τ1 Hya AB |
τ1 Hya A | |
τ1 Hya B |
Tau1 Hydrae is a triple star [3] system in the equatorial constellation of Hydra. Based upon the annual parallax shift of the two visible components as seen from Earth, [1] they are located about 18 parsecs (59 ly) from the Sun. The system has a combined apparent visual magnitude of +4.59, [2] which is bright enough to be visible to the naked eye at night.
The inner pair of stars form a single-lined spectroscopic binary with an orbital period of about 2,807 days and an eccentricity of 0.33. [8] The visible member of the pair, component A, is a visual magnitude 4.60 [2] F-type main sequence star with a stellar classification of F6 V. [3] During the 1990s, it was thought to be a Gamma Doradus variable, but this was later discounted as it shows no short-term photometric variability. The star does show some long-term variability, possibly as a result of a magnetic activity cycle similar to the solar cycle. [13]
The tertiary member, component B, is a visual magnitude 7.15 [2] K-type star with a class of K0. [3] It lies at a separation of 1,120 AU from the primary. [14] As of 2012, it was positioned at an angular separation of 67.5 arc seconds along a position angle of 4°. [15]
{{
cite web}}
: CS1 maint: postscript (
link)