Iota Hydrae

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Iota Hydrae
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Hydra
Right ascension 09h 39m 51.36145s[1]
Declination −01° 08′ 34.1135″[1]
Apparent magnitude (V) 3.91[2]
Spectral type K2.5 III[2]
B−V color index 1.32
Variable type Suspected[3]
Radial velocity (Rv) +24.19±0.36[4] km/s
Proper motion (μ) RA: +46.96[1] mas/yr
Dec.: −62.39[1] mas/yr
Parallax (π) 12.39 ± 0.14[1] mas
Distance 263 ± 3 ly
(80.7 ± 0.9 pc)
Mass 1.92[2] M
Radius 33[4] R
Luminosity 83[2] L
Surface gravity (log g) 2.2[4] cgs
Temperature 4,244±32[2] K
Metallicity [Fe/H] −0.05[2] dex
Rotational velocity (v sin i) 4.5[4] km/s
Age 2.47[2] Gyr
Other designations
ι Hya, 35 Hydrae, BD−00° 2231, FK5 1250, HD 83618, HIP 47431, HR 3845, SAO 137035.[5]
Database references

Iota Hydrae (ι Hya) is a star in the constellation Hydra, about 8° to the north-northwest of Alphard[6] and just to the south of the celestial equator.[7] Visible to the naked eye, it is a suspected variable star with an apparent visual magnitude that ranges between 3.87 and 3.91.[3] Based upon an annual parallax shift of 12.39 mas,[1] it is located around 263 light years from the Sun.

This is an evolved K-type giant star with a stellar classification of K2.5 III.[2] It is a Barium star, which means that, for a giant star, it displays unusually strong absorption lines of singly-ionized barium and strontium.[8] Iota Hydrae has nearly twice[2] the mass of the Sun and has expanded to 33 times the Sun's radius.[4] It is around 2.5 billion years old and is spinning with a leisurely projected rotational velocity of 4.5[4] km/s. It may be a member of the Wolf 630 moving group of stars that share a common trajectory through space.[9]


  1. ^ a b c d e f van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d e f g h i Luck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 23, arXiv:1507.01466Freely accessible, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, 88. 
  3. ^ a b Samus, N. N.; Durlevich, O. V.; et al. (2009), General Catalogue of Variable Stars, 1, Bibcode:2009yCat....102025S. 
  4. ^ a b c d e f 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. 
  5. ^ "iot Hya -- Variable Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-01-04. 
  6. ^ O'Meara, Steve (2007), Herschel 400 Observing Guide, Cambridge University Press, p. 84, ISBN 0521858933. 
  7. ^ Moore, Patrick (2013), The Observer’s Year: 366 Nights of the Universe, The Patrick Moore Practical Astronomy Series, Springer Science & Business Media, p. 71, ISBN 1447136136. 
  8. ^ Lu, Phillip K. (June 1991), "Taxonomy of barium stars", Astronomical Journal, 101: 2229−2254, Bibcode:1991AJ....101.2229L, doi:10.1086/115845. 
  9. ^ McDonald, A. R. E.; Hearnshaw, J. B. (August 1983), "The Wolf 630 moving group of stars", Monthly Notices of the Royal Astronomical Society, 204: 841−852, Bibcode:1983MNRAS.204..841M, doi:10.1093/mnras/204.3.841.