UY Scuti
{{Short description|Star in the constellation Scutum}}
{{Sky|18|27|36.53|-|12|27|58.9|2360000}}
{{other uses|UY Scuti (disambiguation)}}
{{pp|small=yes}}
{{Starbox begin
| name = UY Scuti}}
{{Starbox image
| image = 300px
| caption = DSS2 image of red supergiant star UY Scuti (brightest star in the image), surrounded by a dense starfield
}}
{{Starbox observe
| epoch =J2000
| equinox =J2000
| constell = Scutum
}}
{{Starbox character
| type= Red supergiant
| class= M2-M4Ia-Iab{{cite web |title=VSX: Detail for UY Sct |publisher=American Association of Variable Star Observers |url=https://www.aavso.org/vsx/index.php?view=detail.top&oid=34154 |access-date=2018-09-20}}
| variable=SRc
}}
{{Starbox astrometry
| radial_v={{val|18.33|0.82}}{{cite DR2|4152993273702130432}}
| parallax = 0.5166
| p_error = 0.0494
| parallax_footnote = {{cite Gaia EDR3|4152993273702130432}}
| dist_ly = {{val|5871|534|446|fmt=commas}}
| dist_pc = {{val|1800|164|137|fmt=commas}}
}}
{{Starbox detail
}}
{{Starbox catalog
| names=UY Sct, BD−12°5055, IRC −10422, RAFGL 2162, HV 3805
}}
{{Starbox reference
| Simbad=UY+Sct
}}
{{Starbox end}}
UY Scuti (BD-12°5055) is a red supergiant star, located 5,900 light-years away in the constellation Scutum. It is also a pulsating variable star, with a maximum brightness of magnitude 8.29 and a minimum of magnitude 10.56, which makes it too dim for naked-eye visibility. It is considered to be one of the largest known stars, with a radius estimated at {{convert|909|solar radius|e6km au|sigfig=3|abbr=off|lk=on}}, thus a volume of 750 million times that of the Sun. This estimate implies if it were placed at the center of the Solar System, its photosphere would extend past the orbit of Mars or even the asteroid belt.
Nomenclature and history
File:UYSctLightCurve.png light curve for UY Scuti, plotted from ASAS data]]
UY Scuti was first catalogued in 1860 by German astronomers at the Bonn Observatory, who were completing a survey of stars for the Bonner Durchmusterung Stellar Catalogue.[http://cdsarc.u-strasbg.fr/viz-bin/Cat?cat=I%2F122&target=http& Bonner Durchmusterung (Argelander 1859–1862)] (clicking on "bd.gz" downloads the gzipped 10.1{{nbsp}}MB catalogue) It was designated BD-12°5055, the 5,055th star between 12°S and 13°S counting from 0h right ascension.
On detection in the second survey, the star was found to have changed slightly in brightness, suggesting that it was a new variable star. In accordance with the international standard for designation of variable stars, it was called UY Scuti, denoting it as the 38th variable star of the constellation Scutum.{{cite journal|bibcode=1927KVeBB...1....1P|title=Katalog und Ephemeriden veraenderlicher Sterne fuer 1927|journal=Kleine Veroeffentlichungen der Universitaetssternwarte zu Berlin Babelsberg|volume=1|pages=1.i|last1=Prager|first1=R.|year=1927}}
UY Scuti is located a few degrees north of the A-type star Gamma Scuti and northeast of the Eagle Nebula. Although the star is very luminous, it is, at its brightest, only 9th magnitude as viewed from Earth, due to its distance and location in the Zone of Avoidance within the Cygnus rift.{{cite web|title=UY Sct (UY Scuti)|url=http://www.kusastro.kyoto-u.ac.jp/vsnet/gcvs2/SCTUY.html|website=kusastro|access-date=15 January 2016}}
Characteristics
File:New shot of UY Scuti, the former largest known star v2.png
UY Scuti is a dust-enshrouded bright red supergiant{{cite journal|bibcode=2005A&A...438..273V|arxiv=astro-ph/0504379|title=An empirical formula for the mass-loss rates of dust-enshrouded red supergiants and oxygen-rich Asymptotic Giant Branch stars|journal=Astronomy and Astrophysics|volume=438|pages=273–289|last1=Van Loon|first1=J. Th.|last2=Cioni|first2=M.-R. L.|last3=Zijlstra|first3=A. A.|last4=Loup|first4=C.|year=2005|issue=1|doi=10.1051/0004-6361:20042555|s2cid=16724272}} and is classified as a semiregular variable with an approximate pulsation period of 740 days.{{cite journal |last1=Kholopov |first1=P. N. |last2=Samus |first2=N. N. |last3=Kazarovets |first3=E. V. |last4=Perova |first4=N. B. |year=1985 |title=The 67th Name-List of Variable Stars |journal=Information Bulletin on Variable Stars |volume=2681 |page=1 |bibcode=1985IBVS.2681....1K}}{{cite journal| bibcode=1978JAVSO...7...71W| title=Observations of Three Variable Stars in Scutum| journal=The Journal of the American Association of Variable Star Observers| volume=7| issue=2| pages=71| last1=Whiting| first1=Wendy A.| year=1978}}{{Cite journal | last1 = Jura | first1 = M. | last2 = Kleinmann | first2 = S. G. | doi = 10.1086/191488 | title = Mass-losing M supergiants in the solar neighborhood | journal = The Astrophysical Journal Supplement Series | volume = 73 | pages = 769 | year = 1990 | bibcode = 1990ApJS...73..769J | doi-access = free }} Based on an old radius of {{solar radius|1,708}}, this pulsation would be an overtone of the fundamental pulsation period, or it may be a fundamental mode corresponding to a smaller radius.{{cite journal |doi=10.3847/1538-4357/abb8db |title=Standing on the Shoulders of Giants: New Mass and Distance Estimates for Betelgeuse through Combined Evolutionary, Asteroseismic, and Hydrodynamic Simulations with MESA |year=2020 |last1=Joyce |first1=Meridith |last2=Leung |first2=Shing-Chi |last3=Molnár |first3=László |last4=Ireland |first4=Michael |last5=Kobayashi |first5=Chiaki |last6=Nomoto |first6=Ken'Ichi |journal=The Astrophysical Journal |volume=902 |issue=1 |page=63 |arxiv=2006.09837 |bibcode=2020ApJ...902...63J |s2cid=221507952 |doi-access=free }}
In mid 2012, AMBER interferometry with the Very Large Telescope (VLT) in the Atacama Desert in Chile was used to measure the parameters of three red supergiants near the Galactic Center region: UY Scuti, AH Scorpii, and KW Sagittarii. They determined that all three stars are over 1,000 times bigger than the Sun and over 100,000 times more luminous than the Sun. The stars' sizes were calculated using the Rosseland radius, the location at which the optical depth is {{frac|2|3}},{{cite journal |last1=Wehrse |first1=R. |last2=Scholz |first2=M. |last3=Baschek |first3=B. |date=June 1991 |title=The parameters R and Teff in stellar models and observations |journal=Astronomy and Astrophysics |volume=246 |issue=2 |pages=374–382 |bibcode=1991A&A...246..374B}} with distances adopted from earlier publications. UY Scuti was analyzed to be the largest and the most luminous of the three stars measured, at {{convert|1,708|+/-|192|solar radius|km AU|abbr=on|lk=on}} based on an angular diameter of {{val|5.48|0.10|ul=mas}} and an assumed distance of {{val|2.9|0.317|ul=kiloparsecs}} (kpc) (about {{val|9,500|1,030|u=light-years|fmt=commas}}) which was originally derived in 1970 based on the modelling of the spectrum of UY Scuti. The luminosity is then calculated to be {{solar luminosity|340,000|link=y}} at an effective temperature of {{val|fmt=commas|3,365|134|ul=K}}, giving an initial mass of {{solar mass|25}} (possibly up to {{solar mass|40}} for a non-rotating star).
A 2023 measurement based on the multimessenger monitoring of supernovae, puts the radius at a smaller value of {{solar radius|909}}, together with a smaller luminosity of {{solar luminosity|124,000}} and effective temperature of 3,550{{nbsp}}K. Direct measurements of the parallax of UY Scuti published in the Gaia Data Release 2 give a parallax of {{val|0.6433|0.1059|ul=mas}}, implying a closer distance of approximately {{convert|1.5|kpc|ly}},{{cite journal |last1=Bailer-Jones |first1=C. A. L. |last2=Rybizki |first2=J. |last3=Fouesneau |first3=M. |last4=Mantelet |first4=G. |last5=Andrae |first5=R. |year=2018 |title=Estimating Distance from Parallaxes. IV. Distances to 1.33{{nbsp}}Billion Stars in Gaia Data Release 2 |journal=The Astronomical Journal |volume=156 |issue=2 |pages=58 |arxiv=1804.10121 |bibcode=2018AJ....156...58B |doi=10.3847/1538-3881/aacb21 |s2cid=119289017 |doi-access=free}} and consequently much lower luminosity and radius values of around {{solar luminosity|86,300–87,100}} and {{solar radius|755}} respectively.{{cite journal |last1=Messineo |first1=M. |last2=Brown |first2=A. G. A. |year=2019 |title=A Catalog of Known Galactic K-M Stars of Class I Candidate Red Supergiants in Gaia DR2 |journal=The Astronomical Journal |volume=158 |issue=1 |pages=20 |arxiv=1905.03744 |bibcode=2019AJ....158...20M |doi=10.3847/1538-3881/ab1cbd |s2cid=148571616 |doi-access=free}} However, the Gaia parallax might be unreliable due to a very high level of astrometric noise.
The distance of UY Scuti has been re-measured by Bailer-Jones et al. in 2021, based on a method that uses the stellar parallax from Gaia EDR3, its color and apparent brightness, giving it a much closer distance of {{convert|1800|pc|ly|abbr=on}}.
UY Scuti has no known companion star and so its mass is uncertain. However, it is expected on theoretical grounds to be between {{solar mass|7 and 10}}. Mass is being lost at {{solar mass|{{val|5.8|e=-5}}}} per year, leading to an extensive and complex circumstellar environment of gas and dust.{{Cite journal | last1 = Sylvester | first1 = R. J. | last2 = Skinner | first2 = C. J. | last3 = Barlow | first3 = M. J. | doi = 10.1046/j.1365-8711.1998.02078.x | title = Silicate and hydrocarbon emission from Galactic M supergiants | journal = Monthly Notices of the Royal Astronomical Society | volume = 301 | issue = 4 | pages = 1083–1094 | year = 1998 | bibcode = 1998MNRAS.301.1083S | doi-access = free | url = https://discovery.ucl.ac.uk/10096081/1/sylvester98_msgts.pdf }}
Supernova
Based on current models of stellar evolution, UY Scuti has begun to fuse helium and continues to fuse hydrogen in a shell around the core. The location of UY Scuti deep within the Milky Way disc suggests that it is a metal-rich star.{{cite book|editor-last=Israelian|editor-first=Garik|last1=Meynet|first1=Georges|title=The metal-rich universe|date=2008|publisher=Cambridge University Press|location=Cambridge|isbn=9780521879989|url=http://www.cambridge.org/asia/catalogue/catalogue.asp?isbn=9780521879989|access-date=15 January 2016}}
After fusing heavy elements, its core will begin to produce iron, disrupting the balance of gravity and radiation in its core and resulting in a core collapse supernova. It is expected that a star like UY Scuti should evolve back to hotter temperatures to become a yellow hypergiant, luminous blue variable, or a Wolf–Rayet star, creating a strong stellar wind that will eject its outer layers and expose the core, before exploding as a type IIb, IIn, or type Ib/Ic supernova.{{cite journal |bibcode=2013A&A...558A.131G |title=Fundamental properties of core-collapse supernova and GRB progenitors: Predicting the look of massive stars before death |journal=Astronomy & Astrophysics |volume=558 |pages=A131 |last1=Groh |first1=Jose H. |last2=Meynet |first2=Georges |last3=Georgy |first3=Cyril |last4=Ekström |first4=Sylvia |date=2013 |doi=10.1051/0004-6361/201321906|arxiv = 1308.4681 |s2cid=84177572 }}
See also
References
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{{Stars of Scutum}}
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{{DEFAULTSORT:UY Scuti}}
Category:Scutum (constellation)
Category:Semiregular variable stars