Observation data Epoch J2000.0 Equinox J2000.0 ( ICRS) | |
---|---|
Constellation | Hydra |
Right ascension | 08h 43m 13.47499s [1] |
Declination | +03° 23′ 55.1867″ [1] |
Apparent magnitude (V) | 4.294 [2] |
Characteristics | |
Spectral type | B3 V [3] |
U−B color index | −0.726 [2] |
B−V color index | −0.187 [2] |
Variable type | Candidate β Cep [4] |
Astrometry | |
Proper motion (μ) |
RA: −19.39
[1]
mas/
yr Dec.: −1.08 [1] mas/ yr |
Parallax (π) | 5.56 ± 0.24 mas [1] |
Distance | 590 ± 30
ly (180 ± 8 pc) |
Absolute magnitude (MV) | −1.48 [5] |
Details | |
Mass | 7.0±0.1 [6] M☉ |
Radius | 3.9 [7] R☉ |
Luminosity (bolometric) | 2,680 [8] L☉ |
Surface gravity (log g) | 3.933 [9] cgs |
Temperature | 18,630±411 [9] K |
Rotational velocity (v sin i) | 101±5 [9] km/s |
Age | 31.6±3.9 [6] Myr |
Other designations | |
Database references | |
SIMBAD | data |
Eta Hydrae (η Hydrae) is a star in the equatorial constellation of Hydra. With an apparent visual magnitude of 4.3, [2] it is visible to the naked eye. However, it is the faintest of the five stars that form the "head" of the hydra. [11] Based upon an annual parallax shift of 5.56 mas, [1] it is located roughly 590 light years from the Sun.
This is a B-type main sequence star with a stellar classification of B3V. [3] It has been classified as a candidate Beta Cephei variable with a period of 2.2 days, although this designation was rejected by Stankov and Handler (2005). [4] The spectrum shows a slight underabundance of carbon, compared to the Sun. [13] The star is around 32 [6] million years old and is spinning with a projected rotational velocity of 101 [9] km/s. It has an estimated seven [6] times the mass of the Sun and nearly four [7] times the Sun's radius. Eta Hydrae radiates 2,680 [8] times the solar luminosity from its outer atmosphere at an effective temperature of 18,630 [9] K.
This star, along with δ Hya (Lisan al Sudja), ε Hya, ζ Hya, ρ Hya and σ Hya (Minchir), were Ulug Beg's Min al Azʽal, "Belonging to the Uninhabited Spot". [14] According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Min al Azʽal or Minazal were the title for five stars: δ Hya as Minazal I, η Hya as Minazal II, ε Hya as Minazal III, ρ Hya as Minazal IV and ζ Hya as Minazal V (exclude σ Hya). [15]
In Chinese, 柳宿 (Liǔ Sù), meaning Willow, refers to an asterism consisting of η Hydrae, δ Hydra, σ Hydrae, ρ Hydrae, ε Hydrae, ζ Hydrae, ω Hydrae and θ Hydrae [16] Consequently, η Hydrae itself is known as 柳宿三 (Liǔ Sù sān, English: the Third Star of Willow). [17]
The people of Groote Eylandt called Unwala, "The Crab", for the star cluster including this star, δ Hya (Lisan al Sudja), ε Hya, ζ Hya, ρ Hya and σ Hya (Minchir). [18]
Observation data Epoch J2000.0 Equinox J2000.0 ( ICRS) | |
---|---|
Constellation | Hydra |
Right ascension | 08h 43m 13.47499s [1] |
Declination | +03° 23′ 55.1867″ [1] |
Apparent magnitude (V) | 4.294 [2] |
Characteristics | |
Spectral type | B3 V [3] |
U−B color index | −0.726 [2] |
B−V color index | −0.187 [2] |
Variable type | Candidate β Cep [4] |
Astrometry | |
Proper motion (μ) |
RA: −19.39
[1]
mas/
yr Dec.: −1.08 [1] mas/ yr |
Parallax (π) | 5.56 ± 0.24 mas [1] |
Distance | 590 ± 30
ly (180 ± 8 pc) |
Absolute magnitude (MV) | −1.48 [5] |
Details | |
Mass | 7.0±0.1 [6] M☉ |
Radius | 3.9 [7] R☉ |
Luminosity (bolometric) | 2,680 [8] L☉ |
Surface gravity (log g) | 3.933 [9] cgs |
Temperature | 18,630±411 [9] K |
Rotational velocity (v sin i) | 101±5 [9] km/s |
Age | 31.6±3.9 [6] Myr |
Other designations | |
Database references | |
SIMBAD | data |
Eta Hydrae (η Hydrae) is a star in the equatorial constellation of Hydra. With an apparent visual magnitude of 4.3, [2] it is visible to the naked eye. However, it is the faintest of the five stars that form the "head" of the hydra. [11] Based upon an annual parallax shift of 5.56 mas, [1] it is located roughly 590 light years from the Sun.
This is a B-type main sequence star with a stellar classification of B3V. [3] It has been classified as a candidate Beta Cephei variable with a period of 2.2 days, although this designation was rejected by Stankov and Handler (2005). [4] The spectrum shows a slight underabundance of carbon, compared to the Sun. [13] The star is around 32 [6] million years old and is spinning with a projected rotational velocity of 101 [9] km/s. It has an estimated seven [6] times the mass of the Sun and nearly four [7] times the Sun's radius. Eta Hydrae radiates 2,680 [8] times the solar luminosity from its outer atmosphere at an effective temperature of 18,630 [9] K.
This star, along with δ Hya (Lisan al Sudja), ε Hya, ζ Hya, ρ Hya and σ Hya (Minchir), were Ulug Beg's Min al Azʽal, "Belonging to the Uninhabited Spot". [14] According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Min al Azʽal or Minazal were the title for five stars: δ Hya as Minazal I, η Hya as Minazal II, ε Hya as Minazal III, ρ Hya as Minazal IV and ζ Hya as Minazal V (exclude σ Hya). [15]
In Chinese, 柳宿 (Liǔ Sù), meaning Willow, refers to an asterism consisting of η Hydrae, δ Hydra, σ Hydrae, ρ Hydrae, ε Hydrae, ζ Hydrae, ω Hydrae and θ Hydrae [16] Consequently, η Hydrae itself is known as 柳宿三 (Liǔ Sù sān, English: the Third Star of Willow). [17]
The people of Groote Eylandt called Unwala, "The Crab", for the star cluster including this star, δ Hya (Lisan al Sudja), ε Hya, ζ Hya, ρ Hya and σ Hya (Minchir). [18]