Omega Hydrae

Omega Hydrae
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Hydra
Right ascension 09h 05m 58.36642s[1]
Declination +05° 05′ 32.3360″[1]
Apparent magnitude (V) 5.00[2]
Characteristics
Spectral type K2 II-III[3]
U−B color index +1.22[2]
B−V color index +1.22[2]
Astrometry
Radial velocity (Rv)+24.3±0.8[4] km/s
Proper motion (μ) RA: −19.58[1] mas/yr
Dec.: −11.07[1] mas/yr
Parallax (π)3.64 ± 0.31 mas[1]
Distance900 ± 80 ly
(270 ± 20 pc)
Absolute magnitude (MV)−2.19[5]
Details[6]
Mass4.32±0.37 M☉
Radius48.49±5.55 R☉
Luminosity944.3±178.3 L☉
Surface gravity (log g)1.74±0.12 cgs
Temperature4,789[7] K
Metallicity [Fe/H]−0.12±0.10 dex
Rotational velocity (v sin i)2.3[8] km/s
Age180±70 Myr
Other designations
ω Hya, 18 Hydrae, BD+05°2116, HD 77996, HIP 44659, HR 3613, SAO 117420[9]
Database references
SIMBADdata

Omega Hydrae, Latinised from ω Hydrae, is a golden-hued star in the equatorial constellation of Hydra, located to the west-southwest of the brighter star Zeta Hydrae.[10] Based upon an annual parallax shift of just 3.64 mas as seen from Earth, it is located roughly 900 light-years from the Sun. It is faintly visible to the naked eye with an apparent visual magnitude of 5.00.[2]

This is an evolved K-type star with a stellar classification of K2 II-III,[3] which indicates a spectrum showing traits intermediate between the giant and bright giant stages. It is most likely (98% chance) on the horizontal branch, indicating that the star is generating energy through the thermonuclear fusion of helium at its core. With 4.32 times the Sun's mass, it has expanded to around 48 times the radius of the Sun. Omega Hydrae is about 180[6] million years old and spinning with a leisurely projected rotational velocity of 2.3 km/s.[8] The star is radiating roughly 944[6] times the solar luminosity from its photosphere at an effective temperature of 4,789 K.[7]

  1. ^ a b c d e Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Mermilliod1986 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference tetzlaff2011 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference deBruijne2012 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference Reffert2015 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Mcdonald2012 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Lebre2006 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference OMeara2016 was invoked but never defined (see the help page).