{{short description|Variable star in the constellation Centaurus}} {{Starbox begin}} {{Starbox image | image = [[Image:UYCenLightCurve.png|250px]] | caption = A [[Photometric_system#Photometric_letters|visual band]] [[light curve]] for UY Centauri, plotted from [[All Sky Automated Survey for SuperNovae|ASAS-SN]] data<ref name=ASAS-SN/> }} {{Starbox observe | epoch = J2000.0 | constell = [[Centaurus]] | ra = {{RA|13|16|31.830}}<ref name=Gaia_EDR3/> | dec = {{DEC|−44|42|15.76}}<ref name=Gaia_EDR3/> | appmag_v = {{val|6.93|to|9.48}}<ref name=Samus_et_al_2017/> }} {{Starbox character | type = [[Asymptotic giant branch]]<ref name=Guandalini_et_al_2010/> | class = S6/8<ref name=Borisov_et_al_2023/> | b-v = 2.90<ref name=Ducati_2002/> | u-b = 4.06<ref name=Ducati_2002/> | variable = [[Semiregular variable star|SRb]]<ref name=Samus_et_al_2017/> }} {{Starbox astrometry | radial_v = −20.40{{±|1.2}}<ref name=Gontcharov_2006/> | prop_mo_ra = −17.492 | prop_mo_dec = 0.351 | pm_footnote = <ref name=Gaia_EDR3/> | parallax = 1.5075 | p_error = 0.0529 | parallax_footnote = <ref name=Gaia_EDR3/> | absmag_v = }} {{Starbox detail | source = | mass = 1.24{{±|0.02}}<ref name=Borisov_et_al_2023/> | radius = | luminosity = 11,884{{±|1,116|784}}<ref name=Shetye_et_al_2021/> | gravity = | temperature = 3,300{{±|100|300}}<ref name=Shetye_et_al_2021/> | metal_fe = −0.30{{±|0.15}}<ref name=Shetye_et_al_2021/> | rotation = | rotational_velocity = | age_gyr = 3.5{{±|0.1}}<ref name=Borisov_et_al_2023/> }} {{Starbox catalog | names = {{odlist | V=UY Cen | CD=−44° 8539 | GC=17957 | HD=115236 | HIP=64778 | PPM=318310 | SAO=224021 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad = UY+Cen }} {{Starbox end}}

'''UY Centauri''' is a [[variable star]] in the southern [[constellation]] of [[Centaurus]]. It ranges from an [[apparent visual magnitude]] of 6.93 down to 9.48 with a period of 178.4&nbsp;days, making it too faint to readily view with the [[naked eye]] even at peak brightness.<ref name=Samus_et_al_2017/> The distance to this star is approximately 2,160&nbsp;[[light year]]s based on [[stellar parallax|parallax]] measurements,<ref name=Gaia_EDR3/> although it is drifting closer to the Sun with a [[radial velocity]] of −20&nbsp;km/s.<ref name=Gontcharov_2006/>

In 1911, it was announced that [[Williamina Fleming]] had discovered the variability and peculiar spectrum of this star, then known as DM −44° 8539.<ref name=Fleming_Pickering_1911/> It was given its [[variable star designation]], UY Centauri, in 1912.<ref name="Duner1912"/> In 1952, [[Sergei Gaposchkin|S. Gaposchkin]] listed it as a [[Semiregular variable star|semiregular variable]] with a period of 114.6&nbsp;days and a [[stellar classification|class]] of K5p.<ref name=Gaposchkin_1952/> [[Karl Gordon Henize|K. G. Henize]] included it in a list of candidate [[S-type star|S stars]] below declination −25°, although noting it showed unusual spectral features.<ref name=Henize_1960/> In 1971, UY Cen was named the prototype of SC stars, a rare group with spectra that lie between S- and [[Carbon star|C-type stars]].<ref name=Catchpole_Feast_1971/>

This is an [[stellar evolution|evolved]] star on the [[asymptotic giant branch]] that is shedding mass at an estimated rate of {{val|1.70|e=−7|u=Solar mass}}·yr<sup>−1</sup>.<ref name=Guandalini_et_al_2010/> The ratio of carbon to oxygen isotopes in the [[stellar atmosphere]] is almost exactly 1.<ref name=Shetye_et_al_2021/> At this stage, it is expected that most of these expelled atoms become locked up in carbon monoxide gas, preventing further dust formation. However, in 2002, this star was observed to undergo a steep decline in luminosity, dropping by two magnitudes. This was interpreted as an episode of circumstellar dust formation. It may be an indication that UY Cen is starting to evolve away from the SC phase.<ref name=Steinfadt_et_al_2005/>

==References== <references>

<ref name=SIMBAD>{{cite simbad | title=UY Cen | access-date=2024-10-08 | postscript=. | mode = cs2 }}</ref>

<ref name=Gaia_EDR3>{{Cite Gaia EDR3|6088137479477550464}}</ref>

<ref name=Ducati_2002>{{citation | postscript=. | title=Catalogue of Stellar Photometry in Johnson's 11-color system. | last=Ducati | first=J. R. | journal=VizieR Online Data Catalog | series=CDS/ADC Collection of Electronic Catalogues | volume=2237 | year=2002 | bibcode=2002yCat.2237....0D }}</ref>

<ref name=Fleming_Pickering_1911>{{citation | postscript=. | title=Stars Having Peculiar Spectra. 31 New Variable Stars | last1=Fleming | first1=Williamina | last2=Pickering | first2=Edward C. | journal=Harvard College Observatory Circular | volume=167 | pages=1–3 | date=September 1911 | bibcode=1911HarCi.167....1F }}</ref>

<ref name="Duner1912">{{cite journal | last1=Dunér | last2=Hartwig | last3=Müller | title=Benennung von neu entdeckten veränderlichen Sternen | journal=Astronomische Nachrichten | date=June 1912 | volume=191 | issue=19 | pages=341–358 | doi=10.1002/asna.19121911902 | bibcode= 1912AN....191..341.| url=https://articles.adsabs.harvard.edu/pdf/1912AN....191..341. | access-date=21 December 2024}}</ref>

<ref name=Gaposchkin_1952>{{citation | postscript=. | title=Variable stars in Milton field 40 | last=Gaposchkin | first=Sergei | journal=Annals of Harvard College Observatory | volume=115 | pages=181–188 | year=1952 | bibcode=1952AnHar.115..181G }}</ref>

<ref name=Catchpole_Feast_1971>{{citation | postscript=. | title=Spectroscopic observations of SC stars | last1=Catchpole | first1=R. M. | last2=Feast | first2=M. W. | journal=Monthly Notices of the Royal Astronomical Society | volume=154 | page=197 | year=1971 | issue=2 | doi=10.1093/mnras/154.2.197 | doi-access=free | bibcode=1971MNRAS.154..197C }}</ref>

<ref name=Henize_1960>{{citation | postscript=. | title=S stars south of declination -25deg | last=Henize | first=K. G. | journal=Astronomical Journal | volume=65 | page=491 | date=November 1960 | doi=10.1086/108296 | bibcode=1960AJ.....65..491H }}</ref>

<ref name=Samus_et_al_2017>{{citation | postscript=. | display-authors=1 | last1=Samus | first1=N. N. | last2=Kazarovets | first2=E. V. | last3=Durlevich | first3=O. V. | last4=Kireeva | first4=N. N. | last5=Pastukhova | first5=E. N. | title=General Catalogue of Variable Stars | version=5.1 | journal=[[Astronomy Reports]] | year=2017 | volume=61 | issue=1 | pages=80–88 | bibcode=2017ARep...61...80S | s2cid=125853869 | doi=10.1134/S1063772917010085 }}</ref>

<ref name=Gontcharov_2006>{{citation | postscript=. | title=Pulkovo compilation of radial velocities for 35495 stars in a common system | last=Gontcharov | first=G. A. | journal=[[Astronomy Letters]] | year=2006 | volume=32 | issue=11 | pages=759–771 | doi=10.1134/S1063773706110065 | arxiv=1606.08053 | bibcode=2006AstL...32..759G | s2cid=119231169 }}</ref>

<ref name=Borisov_et_al_2023>{{citation | postscript=. | title=New Generation Stellar Spectral Libraries in the Optical and Near-infrared. I. The Recalibrated UVES-POP Library for Stellar Population Synthesis* | display-authors=1 | last1=Borisov | first1=Sviatoslav B. | last2=Chilingarian | first2=Igor V. | last3=Rubtsov | first3=Evgenii V. | last4=Ledoux | first4=Cédric | last5=Melo | first5=Claudio | last6=Grishin | first6=Kirill A. | last7=Katkov | first7=Ivan Yu. | last8=Goradzhanov | first8=Vladimir S. | last9=Afanasiev | first9=Anton V. | last10=Kasparova | first10=Anastasia V. | last11=Saburova | first11=Anna S. | journal=The Astrophysical Journal Supplement Series | volume=266 | issue=1 | page=11 | date=May 1, 2023 | doi=10.3847/1538-4365/acc321 | doi-access=free | issn=0067-0049 | arxiv=2211.09130 | bibcode=2023ApJS..266...11B }}</ref>

<ref name=Shetye_et_al_2021>{{citation | postscript=. | title=S stars and s-process in the Gaia era. II. Constraining the luminosity of the third dredge-up with Tc-rich S stars | display-authors=1 | last1=Shetye | first1=Shreeya | last2=Van Eck | first2=Sophie | last3=Jorissen | first3=Alain | last4=Goriely | first4=Stephane | last5=Siess | first5=Lionel | last6=Van Winckel | first6=Hans | last7=Plez | first7=Bertrand | last8=Godefroid | first8=Michel | last9=Wallerstein | first9=George | journal=Astronomy & Astrophysics | volume=650 | at=id. A118 | date=June 2021 | doi=10.1051/0004-6361/202040207 | arxiv=2104.03161 | bibcode=2021A&A...650A.118S }}</ref>

<ref name=Guandalini_et_al_2010>{{citation | postscript=. | title=Infrared photometry and evolution of mass-losing AGB stars. III. Mass loss rates of MS and S stars | last=Guandalini | first=R. | journal=Astronomy and Astrophysics | volume=513 | pages=A4 | date=April 2010 | bibcode=2010A&A...513A...4G | s2cid=119193286 | doi=10.1051/0004-6361/200911764 | arxiv=1002.2458 }}</ref>

<ref name=Steinfadt_et_al_2005>{{citation | postscript=. | title=A Unique Dust Formation Episode in the SC-Type Star UY Centauri | last1=Steinfadt | first1=Justin D. R. | last2=Clayton | first2=Geoffrey C. | last3=Lloyd Evans | first3=Tom | last4=Williams | first4=Tom | journal=The Publications of the Astronomical Society of the Pacific | volume=117 | issue=835 | pages=950–954 | date=September 2005 | doi=10.1086/432848 | arxiv=astro-ph/0506505 | bibcode=2005PASP..117..950S | display-authors=1 }}</ref>

<ref name=ASAS-SN>{{cite web | url=https://asas-sn.osu.edu/variables/lookup | website=ASAS-SN Variable Stars Database | title=ASAS-SN Variable Stars Database|publisher=ASAS-SN |access-date=12 October 2024}}</ref>

</references>

{{Centaurus}}

<!-- Properties --> [[Category:Carbon stars]] [[Category:S-type stars]] [[Category:Asymptotic-giant-branch stars]] [[Category:Semiregular variable stars]] <!-- Location/catalogues --> [[Category:Centaurus]] [[Category:Durchmusterung objects]] [[Category:Henry Draper Catalogue objects|115236]] [[Category:Hipparcos objects|064778]] [[Category:Objects with variable star designations|Centauri, UY]] [[Category:Astronomical objects discovered in 1911]] [[Category:Discoveries by Williamina Fleming]]