{{Short description|Star in the constellation Hydra}} {{Starbox begin}} {{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=σ Hydrae |x=922|y=98 }} | caption = Location of σ Hydrae (circled in red) }} {{Starbox observe | epoch = [[J2000.0]] | equinox = [[J2000.0]] ([[International Celestial Reference System|ICRS]]) | constell = [[Hydra (constellation)|Hydra]] | ra = {{RA|08|38|45.43747}}<ref name=vanLeeuwen2007/> | dec = {{DEC|+03|20|29.1701}}<ref name=vanLeeuwen2007/> | appmag_v = 4.48<ref name=Mermilliod1986/> }} {{Starbox character | type = [[Horizontal branch]]<ref name=Stock2018/> | class = K2 III<ref name=Houk1999/> | b-v = +1.21<ref name=Mermilliod1986/> | u-b = +1.23<ref name=Mermilliod1986/> | r-i = | variable = }} {{Starbox astrometry | radial_v = {{Val|27.28|0.19}}<ref name=Famaey2005/> | prop_mo_ra = −19.48<ref name=vanLeeuwen2007/> | prop_mo_dec = −15.92<ref name=vanLeeuwen2007/> | parallax = 8.75 | p_error = 0.25 | parallax_footnote = <ref name=vanLeeuwen2007/> | absmag_v = −0.84<ref name=Anderson2012/> }} {{Starbox detail | source = | mass = {{Val|2.83|0.65|0.73}}<ref name=Stock2018/> | radius = {{Val|27.8|2.2|1.8}}<ref name=Stock2018/> | luminosity = {{Val|288|37|35}}<ref name=Stock2018/> | temperature = {{Val|4491|51|fmt=commas}}<ref name=Luck2015/> | gravity = {{Val|2.21|0.13}}<ref name=Prugniel2011/> | metal_fe = {{Val|0.13|0.06}}<ref name=Prugniel2011/> | rotational_velocity = | age_myr = {{Val|440|400|180}}<ref name=Stock2018/> }} {{Starbox catalog | names = Minchir, [[Bayer designation|σ Hya]], [[Flamsteed designation|5 Hydrae]], [[Durchmusterung|BD]]+03°2026, [[FK5]] 1224, [[Henry Draper Catalogue|HD]] 73471, [[Hipparcos Catalogue|HIP]] 42402, [[Bright Star Catalogue|HR]] 3418, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]] 116988<ref name=SIMBAD/> }} {{Starbox reference | Simbad = sig+Hya }} {{starbox end}} '''Sigma Hydrae''' ('''σ Hydrae''', abbreviated '''Sigma Hya''', '''σ Hya'''), also named '''Minchir''' {{IPAc-en|'|m|I|N|k|@r}},<ref name="IAU-LSN"/> is a solitary<ref name=Eggleton2008/> [[star]] in the equatorial [[constellation]] of [[Hydra (constellation)|Hydra]]. It is visible to the naked eye with an [[Apparent magnitude|apparent visual magnitude]] of 4.48.<ref name=Mermilliod1986/> The estimated distance to this star from the [[Sun]], based upon an annual [[stellar parallax|parallax shift]] of 8.75 [[Minute and second of arc#Symbols and abbreviations|mas]],<ref name=vanLeeuwen2007/> is around 370 [[light-year]]s. At that distance, the visual magnitude of the star is diminished by an interstellar [[extinction (astronomy)|extinction factor]] of 0.16,<ref name=Famaey2005/> due to intervening dust.
== Nomenclature ==
''σ Hydrae'' ([[Latinisation of names|Latinised]] to ''Sigma Hydrae'') is the system's [[Bayer designation]].
It bore the traditional name ''Minchir'', appearing as ''Minchir es-schudscha'' in [[Johann Elert Bode|Bode]]'s large [[Celestial cartography|star atlas]], ''Uranographia''. The name which derived from the [[Arabic]] appelationمنخر الشجاع ''minkhar ash-shujāʽ'' "the nostril brave one" (the hydra) for this star. The name is erroneously{{citation needed|date=May 2017}} spelt as ''Al Minliar al Shuja'' in the [[Yale University|Yale]] ''[[Bright Star Catalogue]]''.<ref>{{Citation | postscript=. |url=http://vizier.u-strasbg.fr/viz-bin/VizieR?-6N&-out.form=H0&//*&-source%3DV/50/notes&HR%3D3418|title = VizieR Service}}</ref> In 2016, the IAU organized a [[IAU Working Group on Star Names|Working Group on Star Names]] (WGSN)<ref name="WGSN">{{citation | postscript=. | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN)|access-date=22 May 2016}}</ref> to catalog and standardize proper names for stars. The WGSN approved the name ''Minchir'' for this star on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.<ref name="IAU-LSN"/>
This star, along with [[Delta Hydrae]] (Lisan al Shudja), [[Epsilon Hydrae]], [[Zeta Hydrae]], [[Eta Hydrae]] and [[Rho Hydrae]], were Ulug Beg's ''Min al Azʽal'', "Belonging to the Uninhabited Spot".<ref>{{citation | last=Allen | first=R. H. | year=1963 | author-link=Richard Hinckley Allen | title=Star Names: Their Lore and Meaning | url=https://archive.org/details/starnamestheirlo00alle/page/249 | access-date=2010-12-12 | edition=Reprint | publisher=Dover Publications Inc | location=New York, NY | isbn=0-486-21079-0 | page=[https://archive.org/details/starnamestheirlo00alle/page/249 249] | url-access=registration |postscript=.}}</ref> (According to a 1971 [[NASA]] memorandum, ''Min al Azʽal'' or ''Minazal'' were the title for five stars: Delta Hydrae as ''Minazal I'', Eta Hydrae as ''Minazal II'', Epsilon Hydrae as ''Minazal III'', Rho Hydrae as ''Minazal IV'' and Zeta Hydrae as ''Minazal V''.<ref name=Rhoads1971/>)
In [[Chinese language|Chinese]], {{lang|zh|柳宿}} ({{lang|zh-Latn|Liǔ Sù}}), meaning ''[[Willow (Chinese constellation)|Willow]] (asterism)'', refers to an [[Asterism (astronomy)|asterism]] consisting of Sigma Hydrae, Delta Hydrae, Eta Hydrae, Rho Hydrae, Epsilon Hydrae, Zeta Hydrae, [[Omega Hydrae]] and [[Theta 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, Sigma Hydrae itself is known as {{lang|zh|柳宿二}} ({{lang|zh-Latn|Liǔ Sù èr}}, {{langx|en|the Second Star of Willow}}).<ref>{{in lang|zh}} [http://aeea.nmns.edu.tw/2006/0605/ap060528.html AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 28 日] {{Webarchive|url=https://web.archive.org/web/20110522112415/http://aeea.nmns.edu.tw/2006/0605/ap060528.html |date=2011-05-22 }}</ref>
The people of [[Groote Eylandt]], used the name ''Unwala'' ("The Crab") for the star cluster including this star, Delta Hydrae (Lisan al Shudja), Epsilon Hydrae (Ashlesha), Zeta Hydrae, Eta Hydrae and Rho Hydrae.<ref name=Selin1997/>
== Properties ==
This is an [[stellar evolution|evolved]] [[Stellar classification#Class K|K-type]] [[giant star]] with a [[stellar classification]] of K2 III.<ref name=Houk1999/> It is likely on the [[horizontal branch]], generating energy by the thermonuclear fusion of [[helium]]. It has 2.8 times the [[mass of the Sun]], 28 times the [[Sun's radius]] and radiates 290 times the [[solar luminosity]] from its [[photosphere]]<ref name=Stock2018/> at an [[effective temperature]] of 4,491 K.<ref name=Luck2015/> Sigma Hydrae is around 440 million years old.<ref name=Luck2015/>
==References== <references> <ref name=vanLeeuwen2007>{{citation | title=Validation of the new Hipparcos reduction | last1=van Leeuwen | first1=F. | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | date=2007 | arxiv=0708.1752 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 | s2cid=18759600 | postscript=. }}</ref>
<ref name=Anderson2012>{{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 | s2cid=119257644 | postscript=. }}</ref>
<ref name=Eggleton2008>{{citation | last1=Eggleton | first1=P. P. | last2=Tokovinin | first2=A. A. | title=A catalogue of multiplicity among bright stellar systems | journal=[[Monthly Notices of the Royal Astronomical Society]] | volume=389 | issue=2 | pages=869–879 | date=September 2008 | doi=10.1111/j.1365-2966.2008.13596.x | doi-access=free | bibcode=2008MNRAS.389..869E | arxiv=0806.2878 | s2cid=14878976 | postscript=. }}</ref>
<ref name=Stock2018>{{Citation | title=Precise radial velocities of giant stars. X. Bayesian stellar parameters and evolutionary stages for 372 giant stars from the Lick planet search | display-authors=1 | last1=Stock | first1=Stephan | last2=Reffert | first2=Sabine | last3=Quirrenbach | first3=Andreas | journal=Astronomy & Astrophysics | volume=616 | pages=A33 | date=August 2018 | doi=10.1051/0004-6361/201833111 | issn=0004-6361 | arxiv=1805.04094 | bibcode=2018A&A...616A..33S |postscript=. }}</ref>
<ref name=Prugniel2011>{{citation | display-authors=1 | last1=Prugniel | first1=Ph. | last2=Vauglin | first2=I. | last3=Koleva | first3=M. | title=The atmospheric parameters and spectral interpolator for the MILES stars | journal=Astronomy & Astrophysics | volume=531 | page=A165 |date=July 2011 | doi=10.1051/0004-6361/201116769 | bibcode=2011A&A...531A.165P | postscript=. | arxiv=1104.4952 | s2cid=54940439 }}</ref>
<ref name=Luck2015>{{citation | title=Abundances in the Local Region. I. G and K Giants | last1=Luck | first1=R. Earle | journal=The Astronomical Journal | volume=150 | issue=3 | id=88 | pages=23 | date=September 2015 | doi=10.1088/0004-6256/150/3/88 | bibcode=2015AJ....150...88L | arxiv=1507.01466 | s2cid=118505114 | postscript=. }}</ref>
<ref name=Houk1999>{{citation | last1=Houk | first1=N. | last2=Swift | first2=C. | title=Michigan catalogue of two-dimensional spectral types for the HD Stars | journal=Michigan Spectral Survey | postscript=. | volume=5 | year=1999 | bibcode=1999MSS...C05....0H }}</ref>
<ref name=Famaey2005>{{citation | display-authors=1 | last1=Famaey | first1=B. | last2=Jorissen | first2=A. | last3=Luri | first3=X. | last4=Mayor | first4=M. | last5=Udry | first5=S. | last6=Dejonghe | first6=H. | last7=Turon | first7=C. | title=Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters | journal=Astronomy and Astrophysics | arxiv=astro-ph/0409579 | volume=430 | issue=1 | pages=165–186 | date=January 2005 | doi=10.1051/0004-6361:20041272 | bibcode=2005A&A...430..165F | s2cid=17804304 | postscript=. }}</ref>
<ref name=Mermilliod1986>{{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=. }}</ref>
<ref name=SIMBAD>{{cite simbad | title=* sig Hya | access-date=2017-01-08 |mode=cs2 | postscript=. }}</ref>
<ref name=Rhoads1971>{{citation | url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720005197_1972005197.pdf | first1=Jack W. | last1=Rhoads | title=Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars | publisher=Jet Propulsion Laboratory, California Institute of Technology | date=November 15, 1971 | access-date=2017-01-09 | postscript=. }}</ref>
<ref name=Selin1997>{{citation | title=Encyclopaedia of the history of science, technology, and medicine in non-western cultures | editor1-first=Helaine | editor1-last=Selin | editor-link1=Helaine Selin | location=Dordrecht | publisher=Kluwer Academic Publishers | year=1997 | page=105 | isbn=9780792340669 | postscript=. | url=https://books.google.com/books?id=raKRY3KQspsC&pg=PA105 }}</ref>
<ref name="IAU-LSN">{{citation | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars |publisher=IAU.org |access-date=16 December 2017 |postscript=.}}</ref> </references>
{{Stars of Hydra|state=collapsed}}
[[Category:K-type giants]] [[Category:Bayer objects|Hydrae, Sigma]] [[Category:Hydra (constellation)]] [[Category:Stars with proper names|Minchir]] [[Category:Durchmusterung objects|BD+03 2026]] [[Category:Flamsteed objects|Hydrae, 05]] [[Category:Henry Draper Catalogue objects|073471]] [[Category:Hipparcos objects|042402]] [[Category:Bright Star Catalogue objects|3418]]