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α Hydri
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Hydrus
Right ascension 01h 58m 46.1935s[1]
Declination −61° 34′ 11.493″[1]
Apparent magnitude (V) +2.90[2]
Spectral type F0IV[2]
U-B color index +0.189[3]
B-V color index +0.290[3]
Radial velocity (Rv) +7[4] km/s
Proper motion (μ) RA: 262.54[1] mas/yr
Dec.: 26.89[1] mas/yr
Parallax (π) 45.74 ± 0.55[1] mas
Distance 71.3 ± 0.9 ly
(21.9 ± 0.3 pc)
Absolute magnitude (MV) 1.153[5]
Radius 1.8[6] R
Temperature 7,077[5] K
Metallicity \begin{smallmatrix}\left[\frac{Fe}{H}\right]\ =\ 0.11\end{smallmatrix}[5]
Rotational velocity (v sin i) 118[7] km/s
Age 8.1 × 108[5] years
Other designations
Gl 83, HD 12311, HIP 9236, HR 591, IRAS 01572-6148, SAO 248474.[2]

Alpha Hydri (α Hyi / α Hydri) is a star in the constellation Hydrus. It is sometimes informally known as the Head of Hydrus.[8] It should not be confused with Alpha Hydrae in the constellation Hydra. Alpha Hydri is one of only three stars in the constellation Hydrus that is above the fourth visual magnitude. This star can be readily located as it lies to the south and west of the prominent star Achernar in the constellation Eridanus.[9]

Alpha Hydri belongs to spectral class F0V and has apparent magnitude +2.9. It is 1.8 times the radius of the Sun,[6] about 810 million years old,[5] and is approximately 71 light years from Earth. The space velocity components of this star are U = −14, V = −14 and W = -2 km/s.[10]

See also


  1. ^ a b c d e Perryman, M. A. C. et al (April 1997). "The HIPPARCOS Catalogue". Astronomy & Astrophysics 323: L49–L52. Bibcode1997A&A...323L..49P.  
  2. ^ a b c "LTT 1059". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2009-10-13.  
  3. ^ a b Gutierrez-Moreno, Adelina; et al. (1966). A System of photometric standards. 1. Publicaciones Universidad de Chile, Department de Astronomy. pp. 1–17. Retrieved 2009-04-15.  
  4. ^ Wilson, R. E. (1953). General Catalogue of Stellar Radial Velocities. Carnegie Institute of Washington D.C.. Retrieved 2009-09-08.  
  5. ^ a b c d e Lachaume, R.; et al. (August 1999). "Age determinations of main-sequence stars: combining different methods". Astronomy and Astrophysics 348: 897-909. Bibcode1999A&A...348..897L.  
  6. ^ a b Wesselink, A. J.; Paranya, K.; DeVorkin, K. (November 1972). "Catalogue of stellar dimensions". Astronomy and Astrophysics Supplement 7: 257. Bibcode1972A&AS....7..257W.   Via Vizier table II/224/cadars.
  7. ^ Royer, F.; et al. (October 2002). "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i". Astronomy and Astrophysics 393: 897−911. doi:10.1051/0004-6361:20020943.  
  8. ^ Allen, Richard Hinkley (1963). Star Names, Their Lore and Meaning. New York: Dover. p. 377. ISBN 0-486-21079-0.  
  9. ^ Moore, Patrick (2005). The observer's year: 366 nights of the universe (2nd ed.). Springer. p. 4. ISBN 1852338849.  
  10. ^ Gliese, W. (1969). Catalogue of Nearby Stars. Karlsruhe.  


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