Observation data Epoch J2000.0 Equinox J2000.0 ( ICRS) | |
---|---|
Constellation | Hydra |
Right ascension | 08h 48m 25.97057s [1] |
Declination | +05° 50′ 16.1283″ [1] |
Apparent magnitude (V) | 4.34 [2] |
Characteristics | |
Spectral type | A0 Vn [3] |
U−B color index | −0.04 [2] |
B−V color index | −0.04 [2] |
Astrometry | |
Radial velocity (Rv) | +32.8 [4] km/s |
Proper motion (μ) |
RA: −17.33
[1]
mas/
yr Dec.: −29.41 [1] mas/ yr |
Parallax (π) | 9.21 ± 0.21 mas [1] |
Distance | 354 ± 8
ly (109 ± 2 pc) |
Absolute magnitude (MV) | −0.83 [5] |
Details [3] | |
Mass | 3.24±0.05 M☉ |
Radius | 2.0 [6] R☉ |
Luminosity | 242 L☉ |
Temperature | 9,795 K |
Rotational velocity (v sin i) | 128 km/s |
Age | 350 [7] Myr |
Other designations | |
Database references | |
SIMBAD | data |
Rho Hydrae, equally written ρ Hydrae, is a binary star [9] in the equatorial constellation of Hydra. It is visible to the naked eye with an apparent visual magnitude of 4.34. [2] The distance to this system, based upon an annual parallax shift of 9.21 mas, [1] is about 354 light years. At that distance, the visual magnitude is diminished by an interstellar extinction of 0.06 magnitudes, due to intervening dust. [7]
The primary component is an A-type main sequence star with a stellar classification of A0 Vn. [3] It has around double [6] the radius of the Sun and 3.2 times the Sun's mass. Rho Hydrae is around 350 million years old [7] and has a high rate of spin, with a projected rotational velocity of 128 km/s. It radiates 242 times the solar luminosity from its outer atmosphere at an effective temperature of 9,795 K. [3] The companion is a magnitude 11.9 star at an angular separation of 12.1 arc seconds along a position angle of 146°, as of 2000. [10]
This system appears among bright stars in a compact pentagon, resembling a quadrilateral due to the suggestive proximity (close arc distance) to Epsilon Hydrae (ε Hya). This shape in the Greco-Roman tradition, which draws on trading and navigation histories shared with nearby older-recorded astrologies is an asterism that represents the head of the water snake. [11]
This light source, along with comparable strength (apparent magnitude) Epsilon, δ Hya (Lisan al Sudja), ζ Hya, η Hya, and σ Hya (Minchir), were Ulug Beg's Min al Azʽal, "Belonging to the Uninhabited Spot". [12] 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). [13]
In Chinese, 柳宿 (Liǔ Sù), meaning Willow, refers to an asterism consisting of ρ Hydrae, δ Hydra, σ Hydrae, η Hydrae, ε Hydrae, ζ Hydrae, ω Hydrae and θ Hydrae [14] Consequently, ρ Hydrae itself is known as 柳宿四 (Liǔ Sù sì, English: the Fourth Star of Willow). [15]
The people of Groote Eylandt called Unwala, "The Crab", for the star cluster including this star, δ Hya (Lisan al Sudja), ε Hya, η Hya, ζ Hya and σ Hya (Minchir). [16]
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cite web}}
: CS1 maint: postscript (
link)
Observation data Epoch J2000.0 Equinox J2000.0 ( ICRS) | |
---|---|
Constellation | Hydra |
Right ascension | 08h 48m 25.97057s [1] |
Declination | +05° 50′ 16.1283″ [1] |
Apparent magnitude (V) | 4.34 [2] |
Characteristics | |
Spectral type | A0 Vn [3] |
U−B color index | −0.04 [2] |
B−V color index | −0.04 [2] |
Astrometry | |
Radial velocity (Rv) | +32.8 [4] km/s |
Proper motion (μ) |
RA: −17.33
[1]
mas/
yr Dec.: −29.41 [1] mas/ yr |
Parallax (π) | 9.21 ± 0.21 mas [1] |
Distance | 354 ± 8
ly (109 ± 2 pc) |
Absolute magnitude (MV) | −0.83 [5] |
Details [3] | |
Mass | 3.24±0.05 M☉ |
Radius | 2.0 [6] R☉ |
Luminosity | 242 L☉ |
Temperature | 9,795 K |
Rotational velocity (v sin i) | 128 km/s |
Age | 350 [7] Myr |
Other designations | |
Database references | |
SIMBAD | data |
Rho Hydrae, equally written ρ Hydrae, is a binary star [9] in the equatorial constellation of Hydra. It is visible to the naked eye with an apparent visual magnitude of 4.34. [2] The distance to this system, based upon an annual parallax shift of 9.21 mas, [1] is about 354 light years. At that distance, the visual magnitude is diminished by an interstellar extinction of 0.06 magnitudes, due to intervening dust. [7]
The primary component is an A-type main sequence star with a stellar classification of A0 Vn. [3] It has around double [6] the radius of the Sun and 3.2 times the Sun's mass. Rho Hydrae is around 350 million years old [7] and has a high rate of spin, with a projected rotational velocity of 128 km/s. It radiates 242 times the solar luminosity from its outer atmosphere at an effective temperature of 9,795 K. [3] The companion is a magnitude 11.9 star at an angular separation of 12.1 arc seconds along a position angle of 146°, as of 2000. [10]
This system appears among bright stars in a compact pentagon, resembling a quadrilateral due to the suggestive proximity (close arc distance) to Epsilon Hydrae (ε Hya). This shape in the Greco-Roman tradition, which draws on trading and navigation histories shared with nearby older-recorded astrologies is an asterism that represents the head of the water snake. [11]
This light source, along with comparable strength (apparent magnitude) Epsilon, δ Hya (Lisan al Sudja), ζ Hya, η Hya, and σ Hya (Minchir), were Ulug Beg's Min al Azʽal, "Belonging to the Uninhabited Spot". [12] 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). [13]
In Chinese, 柳宿 (Liǔ Sù), meaning Willow, refers to an asterism consisting of ρ Hydrae, δ Hydra, σ Hydrae, η Hydrae, ε Hydrae, ζ Hydrae, ω Hydrae and θ Hydrae [14] Consequently, ρ Hydrae itself is known as 柳宿四 (Liǔ Sù sì, English: the Fourth Star of Willow). [15]
The people of Groote Eylandt called Unwala, "The Crab", for the star cluster including this star, δ Hya (Lisan al Sudja), ε Hya, η Hya, ζ Hya and σ Hya (Minchir). [16]
{{
cite web}}
: CS1 maint: postscript (
link)