Zeta Hydrae
 Location of ζ Hydrae (circled) near the center |
|
| Observation data Epoch J2000.0 Equinox J2000.0 |
|
|---|---|
| Constellation | Hydra |
| Right ascension | 08h 55m 23.62614s[1] |
| Declination | +05° 56′ 44.0354″[1] |
| Apparent magnitude (V) | 3.10[2] |
| Characteristics | |
| Spectral type | G9 II-III[3] (G9II-I;OtH[4]) |
| U−B color index | +0.82[2] |
| B−V color index | +1.00[2] |
| Astrometry | |
| Radial velocity (Rv) | +22.8[5] km/s |
| Proper motion (μ) | RA: –100.06[1] mas/yr Dec.: +15.46[1] mas/yr |
| Parallax (π) | 19.51 ± 0.18[1] mas |
| Distance | 167 ± 2 ly (51.3 ± 0.5 pc) |
| Absolute magnitude (MV) | –0.24[6] |
| Details | |
| Mass | 4.2[7] M☉ |
| Radius | 17.9[8] R☉ |
| Luminosity | 132[8] L☉ |
| Surface gravity (log g) | 2.48[8] cgs |
| Temperature | 4,925[7] K |
| Metallicity [Fe/H] | –0.21[9] dex |
| Rotational velocity (v sin i) | 2.5[9] km/s |
| Age | 400[6] Myr |
| Other designations | |
Zeta Hydrae (ζ Hya, ζ Hydrae) is a solitary star in the equatorial constellation of Hydra. This is a generally faint constellation, so, at an apparent visual magnitude of +3.10,[2] this is the third brightest member after Alphard and Gamma Hydrae. The distance to this star has been measured using the parallax technique, yielding a value of roughly 167 light-years (51 parsecs).[1] At this distance, the visual magnitude of the star is diminished by 0.03 as a result of extinction from intervening gas and dust.[6] The star Delta Hydrae is located 12.9 light-years (4.0 parsecs) from Zeta Hydrae and may be a co-moving companion.[4]
With a stellar classification of G9 II-III,[3] this is an evolved giant star that is radiating 132[8] times the luminosity of the Sun from its outer envelope at an effective temperature of 4,925 K.[7] At this heat, the star glows with the yellow hue of a G-type star.[11] The radius of this star, as measured using interferometry, is about 18 times the Sun's radius.[8] It has an estimated 4.2 times the mass of the Sun[7] and is around 400 million years old.[6]
Name and etymology
This star, along with δ Hya (Lisan al Sudja), ε Hya, η Hya, ρ Hya and σ Hya (Minhar al Shija), 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 ζ Hydrae, δ Hydra, σ Hydrae, η Hydrae, ρ Hydrae, ε Hydrae, ω Hydrae and θ Hydrae[14] Consequently, ζ Hydrae itself is known as 柳宿六 (Liǔ Sù liù, English: the Sixth 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, ρ Hya and σ Hya (Minhar al Shija).[16]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 2.0 2.1 2.2 2.3 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 3.0 3.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 4.0 4.1 Lua error in package.lua at line 80: module 'strict' not found.
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- ↑ 6.0 6.1 6.2 6.3 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 7.0 7.1 7.2 7.3 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 8.0 8.1 8.2 8.3 8.4 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 9.0 9.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
- ↑ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 28 日
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
