{{Short description|Star in the constellation Hydra}} {{Starbox begin | name = κ Hydrae }} {{Starbox image | image = {{Location mark |image=Hydra constellation map.svg|alt=|float=center|width=320 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=κ Hydrae |x=735|y=280 }} | caption = Location of κ Hydrae (circled in red) }} {{Starbox observe | epoch = [[J2000.0]] | equinox = [[J2000.0]] ([[International Celestial Reference System|ICRS]]) | constell = [[Hydra (constellation)|Hydra]] | ra = {{RA|09|40|18.36319}}<ref name=dr3/> | dec = {{DEC|−14|19|56.2396}}<ref name=dr3/> | appmag_v = 5.06<ref name=Nicolet1978/> }} {{Starbox character | type = [[main sequence]]<ref name=dr3/> | class = B4 IV/V<ref name=Tetzlaff2011/> | b-v = −0.15<ref name=Nicolet1978/> | u-b = −0.57<ref name=Nicolet1978/> | r-i = | variable = Suspected<ref name=gcvs2009/><ref name=Rufener1982/> }} {{Starbox astrometry | radial_v = {{Val|20.6|2.0}}<ref name=deBruijne2012/> | prop_mo_ra = −26.481<ref name=dr3/> | prop_mo_dec = −20.240<ref name=dr3/> | parallax = 6.9952 | p_error = 0.1897 | parallax_footnote = <ref name=dr3/> | absmag_v = −0.98<ref name=Zorec1991/> }} {{Starbox detail | source = | mass = {{Val|5.0|0.1}}<ref name=Tetzlaff2011/> | radius = 3.4<ref name=PasinettiFracassini2001/> | luminosity = 328<ref name=Mcdonald2012/> | temperature = {{Val|16150|920|fmt=commas}}<ref name=Soubiran2010/> | gravity = | metal_fe = | rotational_velocity = 115.0<ref name=Abt2002/> | age_myr = {{Val|30.7|3.3}}<ref name=Tetzlaff2011/> }} {{Starbox catalog | names = [[Bayer designation|κ]] Hya, 38 Hydrae, [[Durchmusterung|BD]]−13°2917, [[FK5]] 364, [[Henry Draper Catalogue|HD]] 83754, [[Hipparcos Catalogue|HIP]] 47452, [[Bright Star Catalogue|HR]] 3849, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]] 155388.<ref name=SIMBAD/> }} {{Starbox reference | Simbad = kap+Hya }} {{starbox end}} '''κ Hydrae''', Latinised as '''Kappa Hydrae''', is a solitary<ref name=Eggleton2008/> [[star]] in the equatorial [[constellation]] of [[Hydra (constellation)|Hydra]]. Its [[apparent visual magnitude]] is 5.06,<ref name=Nicolet1978/> which is bright enough to be faintly visible to the naked eye. The distance to this star is around {{cvt|143|pc|ly|order=flip|-1}}, based upon an annual [[stellar parallax|parallax shift]] of 7.0 [[Minute and second of arc|mas]].<ref name=dr3/> It may be a [[variable star]], meaning it undergoes repeated fluctuations in brightness by at least 0.1 magnitude.<ref name=Rufener1982/>
This is an [[stellar evolution|evolving]] [[B-type star]] with a [[stellar classification]] of B4 IV/V,<ref name=Tetzlaff2011/> having a [[luminosity class]] intermediate between a [[subgiant]] and a [[giant star]]. It has an estimated five<ref name=Tetzlaff2011/> times the [[mass of the Sun]] and 3.4 times the [[Sun's radius]].<ref name=PasinettiFracassini2001/> Kappa Hydrae has a high rate of spin with a [[projected rotational velocity]] of 115.0 km/s,<ref name=Abt2002/> and is only about 31 million years old.<ref name=Tetzlaff2011/> The star radiates 328 times the [[solar luminosity]] from its [[stellar atmosphere|outer atmosphere]]<ref name=Mcdonald2012/> at an [[effective temperature]] of 16,150 K.<ref name=Soubiran2010/>
==Name== This star was one of the set assigned by the 16th-century astronomer Al Tizini<ref>{{cite web |last=Turkmani |first=Rim |date=7 July 2011 |title=Arabic Roots of the Scientific Revolution |url=http://www.muslimheritage.com/article/arabic-roots-scientific-revolution |access-date=1 July 2016 |website=Muslim Heritage}}</ref> to '''Al Sharāsīf''' ('''ألشراسيف'''), the Ribs (of Hydra), which included the stars from [[β Crateris]] westward through κ Hydrae.<ref>[https://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Crater*.html Star Names - R.H.Allen p. 182]</ref><ref>[https://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Hydra*.html Star Names - R.H.Allen p. 246]</ref>
According to the catalogue of stars in the ''Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars'', ''Al Sharāsīf'' were the title for two stars: β Crateris as ''Al Sharasīf II'' and κ Hydrae as ''Al Sharasīf I''.<ref name="rhoads1971">{{citation |last=Rhoads |first=Jack W. |title=Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars |date=November 15, 1971 |postscript=. |url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720005197_1972005197.pdf |publisher=Jet Propulsion Laboratory, California Institute of Technology}}</ref>
In [[Chinese language|Chinese]], {{lang|zh|張宿}} ({{lang|zh-Latn|Zhāng Xiù}}), meaning ''[[Extended Net]]'', refers to an [[asterism (astronomy)|asterism]] consisting of Kappa Hydrae, [[Upsilon1 Hydrae]], [[Lambda Hydrae]], [[Mu Hydrae]], [[HD 87344]], and [[Phi1 Hydrae]].<ref>{{in lang|zh}} ''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}}.</ref> Consequently, Kappa Hydrae itself is known as {{lang|zh|張宿五}} ({{lang|zh-Latn|Zhāng Xiù wǔ}}), "the Fifth Star of Extended Net".<ref>{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm 香港太空館 - 研究資源 - 亮星中英對照表] {{webarchive|url=https://web.archive.org/web/20081025110153/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm |date=2008-10-25 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.</ref>
==References== <references>
<ref name=dr3>{{cite Gaia DR3|5688852413126934912}}</ref>
<ref name="Zorec1991">{{citation |last1=Zorec |first1=J. |title=Absolute magnitudes of B emission line stars - Correlation between the luminosity excess and the effective temperature |date=May 1991 |journal=Astronomy and Astrophysics |volume=245 |issue=1 |pages=150–170 |postscript=. |bibcode=1991A&A...245..150Z |last2=Briot |first2=D.}}</ref>
<ref name="Rufener1982">{{citation |last1=Rufener |first1=F. |title=List of 333 variable, microvariable or suspected variable stars detected in the Geneva photometry |date=June 1982 |journal=Astronomy and Astrophysics Supplement Series |volume=48 |pages=503–511 |postscript=. |bibcode=1982A&AS...48..503R |last2=Bartholdi |first2=P.}}</ref>
<ref name="PasinettiFracassini2001">{{citation |last1=Pasinetti Fracassini |first1=L. E. |title=Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) |date=February 2001 |journal=Astronomy and Astrophysics |volume=367 |pages=521–524 |postscript=. |edition=3rd |arxiv=astro-ph/0012289 |bibcode=2001A&A...367..521P |doi=10.1051/0004-6361:20000451 |s2cid=425754 |display-authors=1 |last2=Pastori |first2=L. |last3=Covino |first3=S. |last4=Pozzi |first4=A.}}</ref>
<ref name="gcvs2009">{{citation |last1=Samus |first1=N. N. |title=General Catalogue of Variable Stars |date=2009 |journal=VizieR Online Data Catalog |volume=1 |postscript=. |bibcode=2009yCat....102025S |display-authors=etal |last2=Durlevich |first2=O. V.}}</ref>
<ref name="Eggleton2008">{{citation |last1=Eggleton |first1=P. P. |title=A catalogue of multiplicity among bright stellar systems |date=September 2008 |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=389 |issue=2 |pages=869–879 |postscript=. |arxiv=0806.2878 |bibcode=2008MNRAS.389..869E |doi=10.1111/j.1365-2966.2008.13596.x |s2cid=14878976 |last2=Tokovinin |first2=A. A. |doi-access=free}}</ref>
<ref name="Mcdonald2012">{{citation |last1=McDonald |first1=I. |title=Fundamental Parameters and Infrared Excesses of Hipparcos Stars |date=2012 |journal=Monthly Notices of the Royal Astronomical Society |volume=427 |issue=1 |pages=343–57 |postscript=. |arxiv=1208.2037 |bibcode=2012MNRAS.427..343M |doi=10.1111/j.1365-2966.2012.21873.x |s2cid=118665352 |display-authors=1 |last2=Zijlstra |first2=A. A. |last3=Boyer |first3=M. L. |doi-access=free}}</ref>
<ref name="Soubiran2010">{{citation |last1=Soubiran |first1=C. |title=The PASTEL catalogue of stellar parameters |date=June 2010 |journal=Astronomy and Astrophysics |volume=515 |page=A111 |postscript=. |arxiv=1004.1069 |bibcode=2010A&A...515A.111S |doi=10.1051/0004-6361/201014247 |s2cid=118362423 |display-authors=1 |last2=Le Campion |first2=J.-F. |last3=Cayrel de Strobel |first3=G. |last4=Caillo |first4=A.}}</ref>
<ref name="Tetzlaff2011">{{citation |last1=Tetzlaff |first1=N. |title=A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun |date=January 2011 |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=410 |issue=1 |pages=190–200 |postscript=. |arxiv=1007.4883 |bibcode=2011MNRAS.410..190T |doi=10.1111/j.1365-2966.2010.17434.x |s2cid=118629873 |display-authors=1 |last2=Neuhäuser |first2=R. |last3=Hohle |first3=M. M. |doi-access=free}}</ref>
<ref name="deBruijne2012">{{citation |last1=de Bruijne |first1=J. H. J. |title=Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project |date=October 2012 |journal=Astronomy & Astrophysics |volume=546 |pages=14 |postscript=. |arxiv=1208.3048 |bibcode=2012A&A...546A..61D |doi=10.1051/0004-6361/201219219 |s2cid=59451347 |id=A61 |last2=Eilers |first2=A.-C.}}</ref>
<ref name="Nicolet1978">{{citation |last=Nicolet |first=B. |title=Catalogue of homogeneous data in the UBV photoelectric photometric system |date=October 1978 |journal=Astronomy and Astrophysics Supplement Series |volume=34 |pages=1–49 |postscript=. |bibcode=1978A&AS...34....1N}}</ref>
<ref name="Abt2002">{{citation |last1=Abt |first1=Helmut A. |title=Rotational Velocities of B Stars |date=July 2002 |journal=The Astrophysical Journal |volume=573 |issue=1 |pages=359–365 |postscript=. |bibcode=2002ApJ...573..359A |doi=10.1086/340590 |display-authors=1 |last2=Levato |first2=Hugo |last3=Grosso |first3=Monica |doi-access=}}</ref>
<ref name="SIMBAD">{{cite simbad|title=kap Hya|access-date=2017-01-05}}</ref> </references>
{{Stars of Hydra|state=collapsed}}
[[Category:B-type main-sequence stars]] [[Category:B-type subgiants]] [[Category:Suspected variables]] [[Category:Hydra (constellation)]] [[Category:Bayer objects|Hydrae, Kappa]] [[Category:Durchmusterung objects|BD-13 2917]] [[Category:Flamsteed objects|Hydrae, 38]] [[Category:Henry Draper Catalogue objects|083754]] [[Category:Hipparcos objects|047452]] [[Category:Bright Star Catalogue objects|3849]]