Zeta Hydrae

Zeta Hydrae
Diagram showing star positions and boundaries of the Hydra constellation and its surroundings


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
Distance167 ± 2 ly
(51.3 ± 0.5 pc)
Absolute magnitude (MV)–0.24[6]
Details
Mass4.2[7] M☉
Radius17.9[8] R☉
Luminosity132[8] L☉
Surface gravity (log g)2.48[8] cgs
Temperature4,925[7] K
Metallicity [Fe/H]–0.21[9] dex
Rotational velocity (v sin i)2.5[9] km/s
Age400[6] Myr
Other designations
16 Hydrae, BD+06 2060, FK5 334, HD 76294, HIP 43813, HR 3547, SAO 117264.[10]

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. 1 2 3 4 5 6 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357
  2. 1 2 3 4 Jennens, P. A.; Helfer, H. L. (September 1975), "A new photometric metal abundance and luminosity calibration for field G and K giants.", Monthly Notices of the Royal Astronomical Society 172: 667–679, Bibcode:1975MNRAS.172..667J, doi:10.1093/mnras/172.3.667
  3. 1 2 Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics 11 (1): 29–50, Bibcode:1973ARA&A..11...29M, doi:10.1146/annurev.aa.11.090173.000333
  4. 1 2 Shaya, Ed J.; Olling, Rob P. (January 2011), "Very Wide Binaries and Other Comoving Stellar Companions: A Bayesian Analysis of the Hipparcos Catalogue", The Astrophysical Journal Supplement 192 (1): 2, arXiv:1007.0425, Bibcode:2011ApJS..192....2S, doi:10.1088/0067-0049/192/1/2
  5. ↑ Wielen, R.; et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions (35), Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W
  6. 1 2 3 4 Takeda, Yoichi; Sato, Bun'ei; Murata, Daisuke (August 2008), "Stellar parameters and elemental abundances of late-G giants", Publications of the Astronomical Society of Japan 60 (4): 781–802, arXiv:0805.2434, Bibcode:2008PASJ...60..781T, doi:10.1093/pasj/60.4.781
  7. 1 2 3 4 Ando, Hiroyasu; et al. (April 2008), "Detection of Small-Amplitude Oscillations in the G-Giant HD76294 (ξ Hydrae)", Publications of the Astronomical Society of Japan 60 (2): 219–222, Bibcode:2008PASJ...60..219A, doi:10.1093/pasj/60.2.219
  8. 1 2 3 4 5 Ando, Hiroyasu; Tsuboi, Yusuke; Kambe, Eiji; Sato, Bun'ei (August 2010), "Oscillations in G-Type Giants", Publications of the Astronomical Society of Japan 62 (4): 1117–1126, arXiv:1007.1286, Bibcode:2010PASJ...62.1117A, doi:10.1093/pasj/62.4.1117
  9. 1 2 Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209
  10. ↑ "zet Hya -- Star", SIMBAD Astronomical Object Database (Centre de Données astronomiques de Strasbourg), retrieved 2006-11-05
  11. ↑ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16
  12. ↑ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York, NY: Dover Publications Inc, p. 249, ISBN 0-486-21079-0, retrieved 2010-12-12
  13. ↑ Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars (PDF), Jet Propulsion Laboratory, California Institute of Technology
  14. ↑ (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.
  15. ↑ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 28 日
  16. ↑ Selin, Helaine, ed. (1997), Encyclopaedia of the history of science, technology, and medicine in non-western cultures, Dordrecht: Kluwer Academic Publishers, p. 105
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