Upsilon1 Hydrae

{{short description|Star in the constellation Hydra}} {{DISPLAYTITLE:Upsilon¹ Hydrae}} {{other stars by Bayer designation|Upsilon Hydrae{{!}}υ Hydrae}} {{Starbox begin | name = Upsilon¹ Hydrae }} {{Starbox image | image = {{Location mark |image=Hydra constellation map.svg|alt=|float=center|width=300 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=Upsilon1 Hydrae |x=705|y=285 }} | caption = Location of υ¹ Hydrae (circled in red) }} {{Starbox observe | epoch = [[J2000.0]] | constell = [[Hydra (constellation)|Hydra]] | ra={{RA|09|51|28.69384}}<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> | dec={{DEC|-14|50|47.7710}}<ref name=vanLeeuwen2007/> | appmag_v = 4.12<ref name=clpl4_99>{{citation | display-authors=1 | last1=Johnson | first1=H. L. | last2=Iriarte | first2=B. | last3=Mitchell | first3=R. I. | last4=Wisniewskj | first4=W. Z. | title=UBVRIJKL photometry of the bright stars | journal=Communications of the Lunar and Planetary Laboratory | volume=4 | issue=99 | pages=99 | year=1966 | bibcode=1966CoLPL...4...99J | postscript=. }}</ref> }} {{Starbox character | class = G6/8III<ref name="Takeda et al.">{{cite journal | arxiv=0805.2434| author=Takeda | display-authors=etal | 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 | year=2008 | bibcode=2008PASJ...60..781T | doi=10.1093/pasj/60.4.781| s2cid=16258166 }}</ref> | b-v=+0.92<ref name=clpl4_99/> | u-b=+0.65<ref name=clpl4_99/> }} {{Starbox astrometry | radial_v = −14.34<ref name=Jofre2015/> | prop_mo_ra = +18.88<ref name=vanLeeuwen2007/> | prop_mo_dec = −21.85<ref name=vanLeeuwen2007/> | parallax = 12.36 | p_error = 0.26 | parallax_footnote = <ref name=vanLeeuwen2007/> | absmag_v = −0.43<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> }} {{Starbox detail | source = <ref name=Jofre2015>{{citation | last1=Jofré | first1=E. | last2=Petrucci | first2=R. | last3=Saffe | first3=C. | last4=Saker | first4=L. | last5=Artur de la Villarmois | first5=E. | last6=Chavero | first6=C. | last7=Gómez | first7=M. | last8=Mauas | first8=P. J. D. | title=Stellar parameters and chemical abundances of 223 evolved stars with and without planets | journal=Astronomy & Astrophysics | display-authors=1 | volume=574 | pages=A50 | year=2015 | arxiv=1410.6422 | bibcode=2015A&A...574A..50J | doi=10.1051/0004-6361/201424474 | s2cid=53666931 | postscript=. }}</ref> | mass = 3.33 | radius = 14.69 | luminosity = 162 | temperature = 5,185 | rotational_velocity = 2.11 | gravity = 2.95 | metal_fe = 0.10 | age_myr = 270 }} {{Starbox catalog | names = {{odlist | name=Zhang | B=υ¹ Hya | F=39 Hya | BD=−14°2963 | HD=85444 | HIP=48356 | HR=3903 | SAO=155542}} }} {{Starbox reference |Simbad=39+Hya }} {{Starbox end}}

'''Upsilon¹ Hydrae''', [[Latinisation of names|Latinised]] from υ¹ Hydrae (Ups¹ Hya'', ''υ¹ Hya) formally named '''Zhang''',<ref name="IAU-LSN">{{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars | publisher=IAU.org | access-date=16 December 2017 | archive-date=10 March 2025 | archive-url=https://web.archive.org/web/20250310063743/https://www.iau.org/public/themes/naming_stars/ | url-status=dead }}</ref> is a yellow-hued [[star]] in the [[constellation]] of [[Hydra (constellation)|Hydra]]. It is visible to the naked eye, having an [[apparent visual magnitude]] of 4.12.<ref name=clpl4_99/> Based upon an annual [[stellar parallax|parallax]] shift of 12.36&nbsp;[[milliarcsecond|mas]] as seen from Earth,<ref name=vanLeeuwen2007/> it is located about 264&nbsp;[[light-year]]s from the [[Sun]]. The star is moving closer to the Sun with a [[radial velocity]] of −14.34&nbsp;km/s.<ref name=Jofre2015/> In 2005 it was announced that it had a substellar companion.<ref name="Sato et al."/>

== Nomenclature == ''υ¹ Hydrae'' ([[Latinisation of names|Latinised]] to ''Upsilon¹ Hydrae'', abbreviated ''Ups¹ Hya'', ''υ¹ Hya'') is the star's [[Bayer designation]].

In [[Chinese language|Chinese]], {{lang|zh|張宿}} ({{lang|zh-Latn|Zhāng Xiù}}), meaning ''[[Extended Net (Chinese constellation)|Extended Net]]'', refers to an [[asterism (astronomy)|asterism]] consisting of Upsilon¹ Hydrae, [[Lambda Hydrae]], [[Mu Hydrae]], [[HD 87344]], [[Kappa Hydrae]] and [[Phi1 Hydrae|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, Upsilon¹ Hydrae itself is known as {{lang|zh|張宿一}} ({{lang|zh-Latn|Zhāng Xiù yī}}), "the First 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> In 2016, the [[International Astronomical Union]] (IAU) organized a [[Working Group on Star Names]] (WGSN)<ref name="WGSN">{{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN) | access-date=22 May 2016 | archive-date=13 May 2020 | archive-url=https://web.archive.org/web/20200513221742/https://www.iau.org/science/scientific_bodies/working_groups/280/ | url-status=dead }}</ref> to catalog and standardize proper names for stars. The WGSN approved the name ''Zhang'' for Upsilon¹ Hydrae on 30 June 2017 and it is now so included in the List of IAU-approved Star Names.<ref name="IAU-LSN"/>

== Properties == With a [[stellar classification]] of G6/8&nbsp;III,<ref name="Takeda et al."/> Upsilon¹ Hydrae is an [[stellar evolution|evolved]] [[G-type star|G-type]] [[giant star]]. It has an estimated 3.3 times the [[mass of the Sun]] and has expanded to 14.7 times the [[Sun's radius]]. The star is about 270&nbsp;million years old with a [[projected rotational velocity]] of just 2.11&nbsp;km/s. It is radiating 162 times the [[Sun's luminosity]] from its [[photosphere]] at an [[effective temperature]] of {{val|5185|ul=K|fmt=commas}}.<ref name=Jofre2015/>

== Substellar companion == The [[Okayama Planet Search Program|Okayama Planet Search team]] published a paper in 2005 reporting investigations on [[radial velocity]] variations observed for a set of class G giants and announcing the detection of a [[brown dwarf]] companion in [[orbit]] around Upsilon¹ Hydrae.<ref name="Sato et al.">{{cite journal| author=Sato | display-authors=etal | title=Radial-Velocity Variability of G-Type Giants: First Three Years of the Okayama Planet Search Program| journal=Publications of the Astronomical Society of Japan | volume=57| issue=1 | pages=97–107 | year=2005 | bibcode=2005PASJ...57...97S | doi=10.1093/pasj/57.1.97| doi-access= }}</ref> The [[orbital period]] for this companion is roughly 4.1 years, and it has a high [[orbital eccentricity|eccentricity]] of 0.57. Since the [[inclination]] of the orbit to the line-of-sight is unknown, only a lower bound on the mass can be determined. It has at least 49 times the [[mass of Jupiter]].<ref name="Sato et al."/> {{OrbitboxPlanet begin | name = Upsilon¹ Hydrae }} {{OrbitboxPlanet | exoplanet = [[Upsilon1 Hydrae b|b]] | mass = ≥49 | period = 1,500 | semimajor = 3.9 | eccentricity = 0.57 }} {{Orbitbox end}}

==References== {{reflist}}

{{Stars of Hydra|state=collapsed}}

[[Category:G-type giants]] [[Category:Hydra (constellation)]] [[Category:Bayer objects|Hydrae, Upsilon1]] [[Category:Durchmusterung objects|BD-14 2963]] [[Category:Flamsteed objects|Hydrae, 39]] [[Category:Hipparcos objects|48356]] [[Category:Henry Draper Catalogue objects|085444]] [[Category:Bright Star Catalogue objects|3903]] [[Category:Stars with proper names|Zhang]]