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{{Starbox begin
| name = Omega Hydrae
}}{{Starbox observe
| epoch = J2000.0
| equinox = J2000.0 (ICRS)
| constell = Hydra
| ra = {{RA|09|05|58.36642}}
| dec = {{DEC|+05|05|32.3360}}
| appmag_v = 5.00[3]
}}{{Starbox character
| class = K2 II-III[4]
| b-v = +1.22[3]
| u-b = +1.22[3]
| r-i =
| variable =
}}{{Starbox astrometry
| radial_v = {{Val|+24.3|0.8}}[7]
| prop_mo_ra = −19.58
| prop_mo_dec = −11.07
| parallax = 3.64
| p_error = 0.31
| parallax_footnote =
| absmag_v = −2.19[11]
}}{{Starbox detail
| source = [12]
| mass = {{Val|4.32|0.37}}
| radius = {{Val|48.49|5.55}}
| luminosity = {{Val|944.3|178.3}}
| temperature = 4,789[13]
| gravity = {{Val|1.74|0.12}}
| metal_fe = {{Val|−0.12|0.10}}
| rotational_velocity = 2.3[14]
| age_myr = {{Val|180|70}}
}}{{Starbox catalog
| names = ω Lyr, 18 Hydrae, BD+05°2116, HD 77996, HIP 44659, HR 3613, SAO 117420[15]
}}{{Starbox reference
| Simbad = ome+Hya
}}{{Starbox end}}Omega Hydrae, Latinized 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.[16] 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.[3]This is an evolved K-type star with a stellar classification of K2 II-III,[4] 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[12] million years old and spinning with a leisurely projected rotational velocity of 2.3 km/s.[14] The star is radiating roughly 944[12] times the solar luminosity from its photosphere at an effective temperature of 4,789 K.[13] References1. ^1 {{citation | title=XHIP: An extended hipparcos compilation | last1=Anderson | first1=E. | last2=Francis | first2=Ch. | journal=Astronomy Letters | volume=38 | issue=5 | pages=331 | year=2012 | bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015 | arxiv=1108.4971 | postscript=. }}
2. ^1 {{citation | title=Deep-Sky Companions: The Caldwell Objects | first1=Stephen James | last1=O'Meara | publisher=Cambridge University Press | year=2016 | isbn=1107083974 | page=224 | url=https://books.google.com/books?id=MMfxDAAAQBAJ&pg=PA224 }}
3. ^1 2 {{citation | display-authors=1 | last1=McDonald | first1=I. | last2=Zijlstra | first2=A. A. | last3=Boyer | first3=M. L. | title=Fundamental Parameters and Infrared Excesses of Hipparcos Stars | journal=Monthly Notices of the Royal Astronomical Society | volume=427 | issue=1 | pages=343–57 | year=2012 | postscript=. | bibcode=2012MNRAS.427..343M | arxiv=1208.2037 | doi=10.1111/j.1365-2966.2012.21873.x }}
4. ^1 2 {{citation | last1=Lèbre | first1=A. | last2=de Laverny | first2=P. | last3=Do Nascimento | first3=J. D., Jr. | last4=de Medeiros | first4=J. R. | title=Lithium abundances and rotational behavior for bright giant stars | journal=Astronomy and Astrophysics | display-authors=1 | volume=450 | issue=3 | pages=1173–1179 | date=May 2006 | doi=10.1051/0004-6361:20053485 | bibcode=2006A&A...450.1173L }}
5. ^1 {{citation | last1=de Bruijne | first1=J. H. J. | last2=Eilers | first2=A.-C. | title=Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project | journal=Astronomy & Astrophysics | volume=546 | id=A61 | pages=14 | date=October 2012 | doi=10.1051/0004-6361/201219219 | bibcode=2012A&A...546A..61D | arxiv=1208.3048 | postscript=. }}
6. ^1 2 3 {{citation | display-authors=1 | last1=Reffert | first1=Sabine | last2=Bergmann | first2=Christoph | last3=Quirrenbach | first3=Andreas | last4=Trifonov | first4=Trifon | last5=Künstler | first5=Andreas | title=Precise radial velocities of giant stars. VII. Occurrence rate of giant extrasolar planets as a function of mass and metallicity | journal=Astronomy & Astrophysics | arxiv=1412.4634 | volume=574 | pages=A116 | year=2015 | postscript=. | doi=10.1051/0004-6361/201322360 | bibcode=2015A&A...574A.116R | hdl=10722/215277}}Values are for the higher probability horizontal branch model fit.
7. ^1 2 {{cite journal | title=A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun | journal=Monthly Notices of the Royal Astronomical Society | display-authors=1 | last1=Tetzlaff | first1=N. | last2=Neuhäuser | first2=R. | last3=Hohle | first3=M. M. | volume=410 | pages=190 | year=2011 | bibcode=2011MNRAS.410..190T | doi=10.1111/j.1365-2966.2010.17434.x | arxiv=1007.4883 | postscript=. }}
8. ^1 2 3 4 {{citation | last1=Mermilliod | first1=J.-C. | title=Compilation of Eggen's UBV data, transformed to UBV (unpublished) | journal=Catalogue of Eggen's UBV data | year=1986 | publisher=SIMBAD | bibcode=1986EgUBV........0M | postscript=. }}
9. ^1 {{cite simbad | title=* ome Hya | accessdate=2017-03-17 | postscript=. }}
}}External links
| first1=James B. | last1=Kaler | date=May 8, 2015
| title=Theta Hydrae and Omega Hydrae
| work=Stars | publisher=University of Illinois
| url=http://stars.astro.illinois.edu/sow/thetahya.html }}{{Stars of Hydra|state=collapsed}} 9 : K-type giants|K-type bright giants|Hydra (constellation)|Bayer objects|Flamsteed objects|Durchmusterung objects|Henry Draper Catalogue objects|Hipparcos objects|HR objects |