{{short description|Star in the constellation Hydra}} {{Starbox begin | name = ζ 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=ζ Hydrae |x=875|y=62 }} |caption=Location of ζ Hydrae (circled) }} {{Starbox observe | epoch = [[J2000.0]] | ra = {{RA|08|55|23.62614}}<ref name=aaa474_2_653/> | dec = {{DEC|+05|56|44.0354}}<ref name=aaa474_2_653/> | appmag_v = 3.10<ref name=mnras172_667/> | constell = [[Hydra (constellation)|Hydra]] }} {{Starbox character | class = G9 II-III<ref name=araa11_29/> | b-v = +1.00<ref name=mnras172_667/> | u-b = +0.82<ref name=mnras172_667/> | variable = }} {{Starbox astrometry | radial_v = +22.8<ref name=scfs/> | prop_mo_ra = –100.06<ref name=aaa474_2_653/> | prop_mo_dec = +15.46<ref name=aaa474_2_653/> | parallax = 19.51 | p_error = 0.18 | parallax_footnote = <ref name=aaa474_2_653/> | absmag_v = –0.24<ref name=pasj60_4_781/> }} {{Starbox detail | source = <ref name=Baines2018/> | mass = {{val|3.09|0.1}} | radius = {{val|17.61|0.19}} | metal_fe = –0.21<ref name=aj135_1_209/> | gravity = 2.48<ref name=pasj62_4_1117/> | age_myr = {{val|370|40}} | luminosity = {{val|174.2|9.3}} | temperature = {{val|4996|30|fmt=commas}} | rotational_velocity = 2.5<ref name=aj135_1_209/> }} {{Starbox catalog | names = 16 Hydrae, [[Bonner Durchmusterung|BD]]+06 2060, [[Catalogues of Fundamental Stars|FK5]] 334, [[Henry Draper catalogue|HD]] 76294, [[Hipparcos catalogue|HIP]] 43813, [[Harvard Revised catalogue|HR]] 3547, [[Smithsonian Astrophysical Observatory Star Catalogue|SAO]] 117264<ref name=SIMBAD/> }} {{Starbox reference |Simbad=zet+Hya }} {{Starbox end}} '''Zeta Hydrae''' (ζ Hya, ζ Hydrae) is a solitary [[star]] in the [[Celestial equator|equatorial]] [[constellation]] of [[Hydra (constellation)|Hydra]]. This is a generally faint constellation, so, at an [[apparent visual magnitude]] of +3.10,<ref name=mnras172_667/> this is the [[List of stars in Hydra|third-brightest member]] after [[Alphard]] and [[Gamma Hydrae|Naga]].
==Distance== The distance to this star has been measured using the [[parallax]] technique, yielding a value of roughly {{Convert|167|ly|pc|abbr=off|lk=on}}.<ref name=aaa474_2_653/> At this distance, the [[visual magnitude]] of the star is diminished by 0.03 as a result of [[extinction (astronomy)|extinction]] from intervening gas and dust.<ref name=pasj60_4_781/> [[Delta Hydrae]] is about {{Convert|12.9|ly|pc|abbr=off}} from Zeta Hydrae and may be a largely co-moving object.<ref name=apjss192_1_2/> The star has one of the lower-error margin readings among those of the [[Gaia spacecraft]] which computes a parallax of 20.7182 ± 0.3925 mas and, if correct, a distance of 157 ± 3 light years.<ref name=dr2>{{cite DR2|20583588100208201984}}</ref>
==Characteristics== With a [[stellar classification]] of G9 II-III,<ref name=araa11_29/> this is an [[stellar evolution|evolved]] [[giant star]] that is radiating 174 times the [[solar luminosity|luminosity of the Sun]] from its [[stellar atmosphere|outer envelope]] at an [[effective temperature]] of around 5,000 K.<ref name=Baines2018/> At this heat, the star glows with the yellow hue of a [[Stellar classification#Class G|G-type star]].<ref name=csiro/> The radius of this star, measured using [[interferometry]], is 17.6 times the Sun's radius. It has an estimated 3.1 times the mass of the Sun and is around {{nowrap|370 million years}} old.<ref name=Baines2018/>
==Name and etymology== This star, along with [[Delta Hydrae|δ Hya]] (Lisan al Sudja), [[Epsilon Hydrae|ε Hya]], [[Eta Hydrae|η Hya]], [[Rho Hydrae|ρ Hya]] and [[Sigma Hydrae|σ Hya]] (Minchir), were Ulug Beg's ''Min al Azʽal'', "Belonging to the Uninhabited Spot".<ref name=allen1963/> According to the catalogue of stars in the ''Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars'', ''Min al Azʽal'' or ''Minazal'' were the title for five stars:[[Delta Hydrae|δ Hya]] as ''Minazal I'', [[Eta Hydrae|η Hya]] as ''Minazal II'', [[Epsilon Hydrae|ε Hya]] as ''Minazal III'', [[Rho Hydrae|ρ Hya]] as ''Minazal IV'' and ζ Hya as ''Minazal V'' (exclude [[Sigma Hydrae|σ Hya]]).<ref name=rhoads1971/>
In [[Chinese language|Chinese]], {{lang|zh|柳宿}} ({{lang|zh-Latn|Liǔ Sù}}), meaning ''[[Willow (Chinese constellation)|Willow]]'', refers to an [[asterism (astronomy)|asterism]] consisting of ζ Hydrae, [[Delta Hydrae|δ Hydra]], [[Sigma Hydrae|σ Hydrae]], [[Eta Hydrae|η Hydrae]], [[Rho Hydrae|ρ Hydrae]], [[Epsilon Hydrae|ε Hydrae]], [[Omega Hydrae|ω Hydrae]] and [[Theta Hydrae|θ 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, ζ Hydrae itself is known as {{lang|zh|柳宿六}} ({{lang|zh-Latn|Liǔ Sù liù}}, {{langx|en|the Sixth 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]] called ''Unwala'', "The Crab", for the star cluster including this star, [[Delta Hydrae|δ Hya]] (Lisan al Sudja), [[Epsilon Hydrae|ε Hya]] (Ashlesha), [[Eta Hydrae|η Hya]], [[Rho Hydrae|ρ Hya]] and [[Sigma Hydrae|σ Hya]] (Minchir).<ref name=selin1997/>
== References == <references> <ref name=aaa474_2_653>{{citation | first=F. | last=van Leeuwen |date=November 2007 | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 |arxiv = 0708.1752 | s2cid=18759600 }}</ref>
<ref name=Baines2018>{{citation | title=Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer | last1=Baines | first1=Ellyn K. | last2=Armstrong | first2=J. Thomas | last3=Schmitt | first3=Henrique R. | last4=Zavala | first4=R. T. | last5=Benson | first5=James A. | last6=Hutter | first6=Donald J. | last7=Tycner | first7=Christopher | last8=Belle | first8=Gerard T. van | display-authors=1 | journal=The Astronomical Journal | volume=155 | at=30 | year=2018 | issue=1 | arxiv=1712.08109 | bibcode=2018AJ....155...30B | doi=10.3847/1538-3881/aa9d8b | s2cid=119427037 | doi-access=free }}.</ref>
<ref name=scfs>{{citation | display-authors=1 | title=Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions | last1=Wielen | first1=R. | last2=Schwan | first2=H. | last3=Dettbarn | first3=C. | last4=Lenhardt | first4=H. | last5=Jahreiß | first5=H. | last6=Jährling | first6=R. | journal=Veroeffentlichungen des Astronomischen Rechen-Instituts Heidelberg | publisher=Astronomisches Rechen-Institut Heidelberg | issue=35 | year=1999 | volume=35 | page=1 | bibcode=1999VeARI..35....1W }}</ref>
<ref name=aj135_1_209>{{citation | display-authors=1 | last1=Massarotti | first1=Alessandro | last2=Latham | first2=David W. | last3=Stefanik | first3=Robert P. | last4=Fogel | first4=Jeffrey | title=Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity | journal=The Astronomical Journal | volume=135 | issue=1 | pages=209–231 |date=January 2008 | doi=10.1088/0004-6256/135/1/209 | bibcode=2008AJ....135..209M | s2cid=121883397 | doi-access=free }}</ref>
<ref name=allen1963>{{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 }}</ref>
<ref name=araa11_29>{{citation | last1=Morgan | first1=W. W. | last2=Keenan | first2=P. C. | title=Spectral Classification | journal=Annual Review of Astronomy and Astrophysics | volume=11 | issue=1 | pages=29–50 | year=1973 | doi=10.1146/annurev.aa.11.090173.000333 | bibcode=1973ARA&A..11...29M }}</ref>
<ref name=mnras172_667>{{citation | last1=Jennens | first1=P. A. | last2=Helfer | first2=H. L. | title=A new photometric metal abundance and luminosity calibration for field G and K giants. | journal=[[Monthly Notices of the Royal Astronomical Society]] | volume=172 | pages=667–679 |date=September 1975 | issue=3 | bibcode=1975MNRAS.172..667J | doi=10.1093/mnras/172.3.667| doi-access=free }}</ref>
<ref name=SIMBAD>{{cite simbad | title=zet Hya | access-date=2006-11-05}}</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 }}</ref>
<ref name=selin1997>{{citation | page=105 | url=https://books.google.com/books?id=raKRY3KQspsC | title=Encyclopaedia of the history of science, technology, and medicine in non-western cultures | editor-first=Helaine | editor-last=Selin | editor-link=Helaine Selin | location=Dordrecht | publisher=Kluwer Academic Publishers | year=1997 |isbn = 9780792340669}}</ref>
<ref name=pasj62_4_1117>{{citation | last1=Ando | first1=Hiroyasu | last2=Tsuboi | first2=Yusuke | last3=Kambe | first3=Eiji | last4=Sato | first4=Bun'ei | title=Oscillations in G-Type Giants | journal=Publications of the Astronomical Society of Japan | volume=62 | issue=4 | pages=1117–1126 |date=August 2010 | bibcode=2010PASJ...62.1117A |arxiv = 1007.1286 | doi=10.1093/pasj/62.4.1117| s2cid=118677219 }}</ref>
<ref name=csiro>{{citation | title=The Colour of Stars | date=December 21, 2004 | work=Australia Telescope, Outreach and Education | publisher=Commonwealth Scientific and Industrial Research Organisation | url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html | access-date=2012-01-16 | archive-date=2013-12-03 | archive-url=https://web.archive.org/web/20131203222826/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html | url-status=dead }}</ref>
<ref name=apjss192_1_2>{{citation | last1=Shaya | first1=Ed J. | last2=Olling | first2=Rob P. | title=Very Wide Binaries and Other Comoving Stellar Companions: A Bayesian Analysis of the Hipparcos Catalogue | journal=The Astrophysical Journal Supplement | volume=192 | issue=1 | page=2 |date=January 2011 | doi=10.1088/0067-0049/192/1/2 | bibcode=2011ApJS..192....2S |arxiv = 1007.0425 | s2cid=119226823 }}</ref>
<ref name=pasj60_4_781>{{citation | last1=Takeda | first1=Yoichi | last2=Sato | first2=Bun'ei | last3=Murata | first3=Daisuke | title=Stellar parameters and elemental abundances of late-G giants | journal=Publications of the Astronomical Society of Japan | volume=60 | issue=4 | pages=781–802 |date=August 2008 | bibcode=2008PASJ...60..781T |arxiv = 0805.2434 | doi=10.1093/pasj/60.4.781| s2cid=16258166 }}</ref> </references>
{{Stars of Hydra}}
[[Category:Bayer objects|Hydrae, Zeta]] [[Category:Hydra (constellation)]] [[Category:Stars with proper names|Minazal V]] [[Category:Flamsteed objects|Hydrae, 16]] [[Category:Hipparcos objects|043813]] [[Category:G-type bright giants]] [[Category:Henry Draper Catalogue objects|076294]] [[Category:Bright Star Catalogue objects|3547]] [[Category:Durchmusterung objects]]