{{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=12 Hydrae |x=880|y=295 }} | caption = Location of 12 Hydrae (circled in red) }} {{Starbox observe | epoch = J2000 | constell = [[Hydra (constellation)|Hydra]]<ref name=Anderson2012/> | ra = {{RA|08|46|22.54441}}<ref name=GaiaDR3/> | dec = {{DEC|−13|32|51.8051}}<ref name=GaiaDR3/> | appmag_v = 4.32<ref name=Anderson2012/> }} {{Starbox character | type = [[red giant branch]]<ref name=GaiaDR3/> | class = {{nowrap|G8 IIIb CN-1}}<ref name=Keenan1989/> | b-v = {{Val|0.900|0.015}}<ref name=Anderson2012/> | u-b = | variable = }} {{Starbox astrometry | radial_v = {{Val|−8.5|0.7}}<ref name=Anderson2012/> | prop_mo_ra = +10.316<ref name=GaiaDR3/> | prop_mo_dec = −15.012<ref name=GaiaDR3/> | parallax = 15.8840 | p_error = 0.3987 | parallax_footnote = <ref name=GaiaDR3/> | absmag_v = +0.26<ref name=vonEiff2012/> }} {{Starbox orbit | reference = <ref name=Hartkopf2006/> | primary = Aa | name = Ab | period_unitless = {{Val|1592|806|fmt=commas|u=days}} | axis = {{Val|0.0116|0.057}} | eccentricity = {{Val|0.40|0.26}} | inclination = {{Val|58|10}} | node = {{Val|91|16}} | periastron = {{Val|49194|664|fmt=commas}} | periarg = {{Val|103|34}} }} {{Starbox detail | mass = 1.83<ref name=khalatyan2024/> | radius = 10.8<ref name=tic/> | luminosity = 71<ref name=fetherolf2023/> | temperature = 5,105<ref name=tic/> | gravity = 3.13<ref name=khalatyan2024/> | metal_fe = −0.01<ref name=khalatyan2024/> | rotational_velocity = {{Val|4.6|0.2}}<ref name=vonEiff2012/> | rotation = | age_myr = 410<ref name=GaiaDR3/> }} {{Starbox catalog | names = {{odlist | B=D Hya | F=12 Hya | BD=−13°2673 | HD=74918 | HIP=43067 | HR=3484 | SAO=154622 | WDS=J08464-1333 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad=D+Hya }} {{Starbox end}}
'''12 Hydrae''' is a probable [[astrometric binary]]<ref name=Eggleton2008/> [[star]] system located 205 [[light year]]s away from the Sun in the [[celestial equator|equatorial]] [[constellation]] of [[Hydra (constellation)|Hydra]]. It has the [[Bayer designation]] '''D Hydrae''';<ref name=SIMBAD/> ''12 Hydrae'' is the [[Flamsteed designation]]. This system is visible to the naked eye as a faint, yellow-hued star with a combined [[apparent visual magnitude]] of 4.32.<ref name=Anderson2012/> It is moving closer to the Earth with a heliocentric [[radial velocity]] of −8.5 km/s.<ref name=Anderson2012/>
This was found to be a double star by [[R. A. Rossiter]] in 1953,<ref name=Rossiter1953/> with the magnitude 13.7 companion having an [[angular separation]] of {{Val|26.8|ul=arcsecond}} along a [[position angle]] of 266°, as of 2016. The brighter, magnitude 4.32 component A is a [[spectroscopic binary]]. As of 2009, the orbital solution for this pair is of low quality, giving a [[orbital period|period]] of roughly {{Convert|1592|days|years|0|disp=out|abbr=off}} and an [[orbital eccentricity|eccentricity]] of around 0.4.<ref name=Hartkopf2006/>
The primary component is an aging [[giant star]] with a [[stellar classification]] of {{nowrap|G8 IIIb CN-1}},<ref name=Keenan1989/> where the suffix notation indicates an underabundance of the [[cyanogen]] molecule. It is 410 million years old<ref name=GaiaDR3/> with 1.8 times the [[mass of the Sun]].<ref name=khalatyan2024/> After exhausting the hydrogen at its core and [[stellar evolution|evolving]] off the [[main sequence]], the star has swollen to 11 times the [[Sun's radius]].<ref name=tic/> It is radiating 71 times the [[luminosity of the Sun]]<ref name=fetherolf2023/> from its enlarged [[photosphere]] at an [[effective temperature]] of {{val|fmt=commas|5105|ul=K}}.<ref name=tic/>
==References== <references> <ref name=GaiaDR3>{{cite DR3|5735066776630042112}}</ref>
<ref name=SIMBAD>{{cite simbad | title=12 Hya | access-date=May 1, 2019 }}</ref>
<ref name=tic>{{cite journal |last1=Stassun |first1=Keivan G. |last2=Oelkers |first2=Ryan J. |last3=Paegert |first3=Martin |last4=Torres |first4=Guillermo |last5=Pepper |first5=Joshua |last6=De Lee |first6=Nathan |last7=Collins |first7=Kevin |last8=Latham |first8=David W. |last9=Muirhead |first9=Philip S. |last10=Chittidi |first10=Jay |last11=Rojas-Ayala |first11=Bárbara |last12=Fleming |first12=Scott W. |last13=Rose |first13=Mark E. |last14=Tenenbaum |first14=Peter |last15=Ting |first15=Eric B. |last16=Kane |first16=Stephen R. |last17=Barclay |first17=Thomas |last18=Bean |first18=Jacob L. |last19=Brassuer |first19=C. E. |last20=Charbonneau |first20=David |last21=Ge |first21=Jian |last22=Lissauer |first22=Jack J. |last23=Mann |first23=Andrew W. |last24=McLean |first24=Brian |last25=Mullally |first25=Susan |last26=Narita |first26=Norio |last27=Plavchan |first27=Peter |last28=Ricker |first28=George R. |last29=Sasselov |first29=Dimitar |last30=Seager |first30=S. |display-authors=1 |title=The Revised TESS Input Catalog and Candidate Target List |journal=The Astronomical Journal |date=2019 |volume=158 |issue=4 |page=138 |doi=10.3847/1538-3881/ab3467 |doi-access=free |arxiv=1905.10694 |bibcode=2019AJ....158..138S }}</ref>
<ref name=fetherolf2023>{{cite journal |last1=Fetherolf |first1=Tara |last2=Pepper |first2=Joshua |last3=Simpson |first3=Emilie |last4=Kane |first4=Stephen R. |last5=Močnik |first5=Teo |last6=English |first6=John Edward |last7=Antoci |first7=Victoria |last8=Huber |first8=Daniel |last9=Jenkins |first9=Jon M. |last10=Stassun |first10=Keivan |last11=Twicken |first11=Joseph D. |last12=Vanderspek |first12=Roland |last13=Winn |first13=Joshua N. |title=Variability Catalog of Stars Observed during the TESS Prime Mission |journal=The Astrophysical Journal Supplement Series |date=2023 |volume=268 |issue=1 |page=4 |doi=10.3847/1538-4365/acdee5 |doi-access=free |arxiv=2208.11721 |bibcode=2023ApJS..268....4F }}</ref>
<ref name=khalatyan2024>{{cite journal |last1=Khalatyan |first1=A. |last2=Anders |first2=F. |last3=Chiappini |first3=C. |last4=Queiroz |first4=A. B. A. |last5=Nepal |first5=S. |last6=Dal Ponte |first6=M. |last7=Jordi |first7=C. |last8=Guiglion |first8=G. |last9=Valentini |first9=M. |last10=Torralba Elipe |first10=G. |last11=Steinmetz |first11=M. |last12=Pantaleoni-González |first12=M. |last13=Malhotra |first13=S. |last14=Jiménez-Arranz |first14=Ó. |last15=Enke |first15=H. |last16=Casamiquela |first16=L. |last17=Ardèvol |first17=J. |title=Transferring spectroscopic stellar labels to 217 million Gaia DR3 XP stars with SHBoost |journal=Astronomy and Astrophysics |date=2024 |volume=691 |pages=A98 |doi=10.1051/0004-6361/202451427 |arxiv=2407.06963 |bibcode=2024A&A...691A..98K }}</ref>
<ref name=Keenan1989>{{citation | last1=Keenan | first1=Philip C. | last2=McNeil | first2=Raymond C. | title=The Perkins catalog of revised MK types for the cooler stars | journal=Astrophysical Journal Supplement Series | volume=71 | pages=245 | year=1989 | bibcode=1989ApJS...71..245K | doi=10.1086/191373 }}</ref>
<ref name=vonEiff2012>{{citation | last1=Ammler-von Eiff | first1=Matthias | last2=Reiners | first2=Ansgar | title=New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars? | journal=Astronomy & Astrophysics | arxiv=1204.2459 | volume=542 | page=A116 | date=June 2012 | postscript=. | doi=10.1051/0004-6361/201118724 | bibcode=2012A&A...542A.116A | s2cid=53666672 }}</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 | postscript=. | bibcode=2008MNRAS.389..869E | arxiv=0806.2878 | s2cid=14878976 }}</ref>
<ref name=Hartkopf2006>{{citation | display-authors=1 | last1=Hartkopf | first1=W. I. | last2=Mason | first2=B. D. | last3=Worley | first3=C. E. | date=June 30, 2006 | title=Sixth Catalog of Orbits of Visual Binary Stars | publisher=United States Naval Observatory | url=http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/orb6 | accessdate=2017-06-02 | postscript=. | archive-date=2017-08-01 | archive-url=https://web.archive.org/web/20170801102553/http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/orb6 | url-status=dead }}</ref>
<ref name=Rossiter1953>{{citation | title=Seventh list of new Southern double stars found at the Lamont-Hussey Observatory of the University of Michigan at Bloemfontein, South Africa. | last1=Rossiter | first1=R. A. | journal=Astronomical Journal | postscript=. | volume=58 | pages=29–30 | date=February 1953 | doi=10.1086/106804 | bibcode=1953AJ.....58...29R }}</ref>
<ref name=Anderson2012>{{citation | title=XHIP: An extended hipparcos compilation | last1=Anderson | first1=E. | last2=Francis | first2=Ch. | journal=Astronomy Letters | postscript=. | volume=38 | issue=5 | pages=331 | year=2012 | bibcode=2012AstL...38..331A | arxiv=1108.4971 | doi=10.1134/S1063773712050015 | s2cid=119257644 }}</ref> </references>
{{Stars of Hydra}}
[[Category:Hydra (constellation)]] [[Category:G-type giants]] [[Category:Flamsteed objects|Hydrae, 12]] [[Category:Bayer objects|Hydrae, D]] [[Category:Bright Star Catalogue objects|3484]] [[Category:Henry Draper Catalogue objects|074918]] [[Category:Hipparcos objects|012097]] [[Category:Durchmusterung objects|BD-13 2673]] [[Category:Double stars]] [[Category:Spectroscopic binaries]]