{{Short description|Star in the constellation Hydra}} {{Starbox begin}} {{Starbox image | image = {{Location mark | image=Hydra IAU.svg | float=center | width=280 | position=right | mark=Red circle.svg | mark_width=10 | mark_link=ν Hya | x%=55.6 | y%=46.1 }} | caption=Location of ν Hydrae (circled) }} {{Starbox observe | epoch = J2000 | constell = [[Hydra (constellation)|Hydra]]<ref name=Anderson2012/> | ra = {{RA|10|49|37.48875}}<ref name=aaa474_2_653/> | dec = {{DEC|-16|11|37.1360}}<ref name=aaa474_2_653/> | appmag_v = 3.115<ref name=sps1966/> }} {{Starbox character | type = | class = K0/K1 III<ref name=aaa339_858/> | b-v = +1.239<ref name=sps1966/> | u-b = +1.305<ref name=sps1966/> | variable = }} {{Starbox astrometry | radial_v = {{val|−1.37|0.25}}<ref name=aj135_1_209/> | prop_mo_ra = +93.35<ref name=aaa474_2_653/> | prop_mo_dec = +198.88<ref name=aaa474_2_653/> | parallax = 23.7940 | p_error = 0.1695 | parallax_footnote =<ref name="Gaia3">{{cite Gaia EDR3|3557567320183657472}}</ref> | absmag_v = −0.11<ref name=Anderson2012/> }} {{Starbox detail | mass = 2.0<ref name=aaa352_217/> | radius = 21<ref name=aj135_1_209/> | luminosity = 151<ref name=aj135_1_209/> | temperature = 4,335<ref name=aj135_1_209/> | metal_fe = −0.30<ref name=aj135_1_209/> | rotation = | rotational_velocity = 5.3<ref name=aj135_1_209/> | gravity = 2.3<ref name=aj135_1_209/> | age = }} {{Starbox catalog | names = {{odlist | B=ν Hya | F=4 Crateris | BD=−15 3138 | FK5=410 | HD=93813 | HIP=52943 | HR=4232 | SAO=156256 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad = nu+Hya }} {{Starbox end}}
'''Nu Hydrae''', [[Romanization of Greek|Latinized]] from ν Hydrae, is an orange-hued [[star]] in the [[constellation]] [[Hydra (constellation)|Hydra]], near the border with the neighboring constellation of [[Crater (constellation)|Crater]]. It has an [[apparent visual magnitude]] of 3.115,<ref name=sps1966/> which is bright enough to be seen with the naked eye. Based upon [[parallax]] measurements, this star is located at a distance of about {{Convert|137|ly|pc|abbr=off|lk=on}} from the [[Earth]].<ref name=aaa474_2_653/>
The [[stellar spectrum|spectrum]] of this star matches a [[stellar classification]] of K0/K1 III,<ref name=aaa339_858/> where the [[luminosity class]] of 'III' indicates this is a [[giant star]] that has exhausted the supply of hydrogen at its core and [[stellar evolution|evolved]] away from the [[main sequence]]. The radius of this star has expanded to 21 times the [[solar radius|Sun's radius]]<ref name=aj135_1_209/> and it radiates about 151 times the [[solar luminosity|luminosity of the Sun]].<ref name=aj135_1_209/> This expanded outer envelope has an [[effective temperature]] of about 4,335 K,<ref name=aj135_1_209/> giving it the characteristic orange hue of a K-type star.<ref name=csiro/>
Nu Hydrae is an X-ray emitter with an estimated luminosity of {{nowrap|6.6 × 10<sup>28</sup> [[erg]] s<sup>−1</sup>}} in the X-ray band.<ref name=aaa352_217/> The abundance of elements other than hydrogen and helium, what astronomers term the star's [[metallicity]],<ref name=aj135_1_209/> is about half that in the Sun.{{efn|name=metal}} It has a relatively high [[proper motion]] across the [[celestial sphere]],<ref name=SIMBAD/> suggesting that it has a [[peculiar velocity]] roughly three times higher than its neighbors.<ref name=kaler/>
Nu Hydrae was a later designation of '''4 Crateris'''.<ref>{{cite journal | last=Wagman | first=M. | title=Flamsteed's Missing Stars | journal=Journal for the History of Astronomy |issue=3 | volume=18 | page=215 |date=August 1987 | bibcode=1987JHA....18..209W | doi=10.1177/002182868701800305| s2cid=118445625 }}</ref>
== Notes == {{notelist|refs= {{efn| name=metal|1=The actual abundance of metals relative to the abundance in the Sun can be derived by taking the metallicity estimate to the power of ten, thus: : 10<sup>[Fe/H]</sup> = 10<sup>−0.30</sup> ≈ 0.50}} }}
== References == {{Reflist|40em|refs=
<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=aj135_1_209>{{cite journal | 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 | doi-access=free }}</ref>
<ref name=Anderson2012>{{cite XHIP|52943|mode=cs2|postscript=.}}</ref>
<ref name=sps1966>{{citation | display-authors=1 | last1=Gutierrez-Moreno | first1=Adelina | last2=Moreno | first2=H. | last3=Stock | first3=J. | last4=Torres | first4=C. | last5=Wroblewski | first5=H. | title=A System of photometric standards | journal=Publications of the Department of Astronomy University of Chile | publisher=Publicaciones Universidad de Chile, Department de Astronomy | volume=1 | pages=1–17 | year=1966 | bibcode=1966PDAUC...1....1G }}</ref>
<ref name=aaa352_217>{{citation | last1=Gondoin | first1=P. | title=Evolution of X-ray activity and rotation on G-K giants | journal=Astronomy and Astrophysics | volume=352 | pages=217–227 |date=December 1999 | bibcode=1999A&A...352..217G }}</ref>
<ref name=aaa339_858>{{citation | last1=di Benedetto | first1=G. P. | title=Towards a fundamental calibration of stellar parameters of A, F, G, K dwarfs and giants | journal=Astronomy and Astrophysics | volume=339 | pages=858–871 |date=November 1998 | bibcode=1998A&A...339..858D }}</ref>
<ref name=kaler>{{citation | first1=James B. | last1=Kaler | title=Nu Hydrae | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/nuhya.html | access-date=2012-01-13 }}</ref>
<ref name=SIMBAD>{{citation | title=LTT 3973 -- High proper-motion Star | work=SIMBAD | publisher=[[Centre de Données astronomiques de Strasbourg]] | url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+93813 | access-date=2012-01-13 }}</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-url=https://web.archive.org/web/20131203222826/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html | archive-date=December 3, 2013 | url-status=dead }}</ref>
}}
{{Stars of Hydra}}
[[Category:K-type giants]] [[Category:Hydra (constellation)]] [[Category:Bayer objects|Hydrae, Nu]] [[Category:Durchmusterung objects]] [[Category:Flamsteed objects|Crateris, 04]] [[Category:Henry Draper Catalogue objects|093813]] [[Category:Hipparcos objects|052943]] [[Category:Bright Star Catalogue objects|4232]]