{{Short description|Star in the constellation Musca}} {{Starbox begin}} {{Starbox image | image = [[Image:TUMusLightCurve.png|250px]] | caption = A [[light curve]] for TU Muscae, plotted from ''[[Transiting Exoplanet Survey Satellite|TESS]]'' data<ref name=MAST/> }} {{Starbox observe | epoch = [[J2000.0]] | constell = [[Musca]] | ra = {{RA|11|31|10.92470}}<ref name=hipparcos>{{cite journal|bibcode=2007A&A...474..653V|title=Validation of the new Hipparcos reduction|journal=Astronomy and Astrophysics|volume=474|issue=2|pages=653–664|last1=Van Leeuwen|first1=F.|year=2007|doi=10.1051/0004-6361:20078357|arxiv = 0708.1752 |s2cid=18759600}}</ref> | dec = {{DEC|-65|44|32.1019}}<ref name=hipparcos/> | appmag_v = 8.307<ref name=ubv>{{cite journal|bibcode=2004ApJS..151..103M|title=A Galactic O Star Catalog|journal=The Astrophysical Journal Supplement Series|volume=151|issue=1|pages=103–148|last1=Maíz-Apellániz|first1=Jesús|last2=Walborn|first2=Nolan R. |author2-link=Nolan R. Walborn |last3=Galué|first3=Héctor Á.|last4=Wei|first4=Lisa H.|year=2004|doi=10.1086/381380|arxiv = astro-ph/0311196 |s2cid=118813863}}</ref>{{nowrap|(8.17 - 8.75<ref name=gcvs>{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}</ref>)}} }} {{Starbox character | class = O7V + O8V<ref name=penny08/> | b-v = +0.047<ref name=ubv/> | u-b = −0.860<ref name=ubv/> | variable = [[Beta Lyrae variable|β Lyr]]<ref name=gcvs/> }} {{Starbox astrometry | radial_v = −4<ref name="terrell03"/> | prop_mo_ra = −6.62<ref name=hipparcos/> | prop_mo_dec = −1.21<ref name=hipparcos/> | parallax = 0.02 | p_error = 0.76 | parallax_footnote = <ref name=hipparcos/> | dist_ly = | dist_pc = | absmag_v = | absmag_bol = }} {{Starbox orbit | reference = <ref name=penny08/> | primary = | name = | period = | period_unitless = 1.387 days | axis = | axis_unitless = {{solar radius|17.34}}<ref name=palate>{{cite journal|bibcode=2012A&A...537A.119P|arxiv=1109.1103|title=Spectral modelling of circular massive binary systems. Towards an understanding of the Struve-Sahade effect?|journal=Astronomy & Astrophysics|volume=537|pages=A119|last1=Palate|first1=M.|last2=Rauw|first2=G.|year=2012|doi=10.1051/0004-6361/201117520|s2cid=84840295}}</ref> | eccentricity = 0 | inclination = 77.7 | node = 3.137<ref name="terrell03"/> | periastron = | periarg = | periarg_primary = | k1 = 214.5 | k2 = 345.8 }} {{Starbox detail | source=<ref name=penny08/> | component1 = Primary | mass = 16.8 | radius = 7.2 | luminosity = 105,000 | gravity = 4.05<ref name=palate/> | temperature = 35,000<ref name="terrell03"/> | metal = | metal_fe = | rotation = | rotational_velocity = | age_myr = | component2 = secondary | mass2 = 10.5 | radius2 = 5.7 | luminosity2 = 35,000 | gravity2 = 4.04<ref name=palate/> | temperature2 = 31,366<ref name="terrell03"/> | metal2 = | metal_fe2 = | rotation2 = | rotational_velocity2 = | age_myr2 = }} {{Starbox catalog | names = [[Variable star designation|TU]]&nbsp;Muscae, [[Hipparcos|HIP]]&nbsp;56196, [[Henry Draper Catalogue|HD]]&nbsp;100213, [[Cordoba Durchmusterung|BD]]−65°1101, [[2MASS]]&nbsp;J11311091-6544322 | component1 = <!-- Double star component 1 primary designation --> | names1 = <!-- Other catalog designations for component 1 --> | component2 = <!-- Double star component 2 primary designation --> | names2 = <!-- Other catalog designations for component 2--> }} {{Starbox reference | Simbad = TU+Mus }} {{starbox end}}

'''TU Muscae''', also known as '''HD 100213''', is an [[eclipsing binary]] [[star]] in the [[constellation]] [[Musca]]. Its [[apparent magnitude]] ranges from 8.17 to 8.75 over around 1.4 days.<ref name=gcvs/>

==Physical description== TU Muscae is a remote [[binary star]] system made up of two hot luminous blue main sequence stars of spectral types O7.5V and O9.5V, with masses 23 and 15 times that of the Sun. The stars are so close that they are in contact with each other ([[Contact binary|overcontact binary]]) and are classed as a [[Beta Lyrae variable]] as their light varies from earth as they eclipse each other.<ref name="terrell03"/> The spectra indicate they are hot stars, with surface temperatures of roughly 37200 and 34700 K respectively. They are both still on the [[main sequence]] of star evolution, burning their core hydrogen. Astronomers Laura Penny and Cynthia Ouszt proposed the two were originally more equal in size but as they became close enough so that material from the less massive star began transferring to the more massive star via [[Roche lobe|Roche-lobe]] overflow. However they concede that figuring out the evolution of interacting massive binary systems is "a little like trying to unspill milk".<ref name="penny08">{{cite journal|author=Penny, Laura R.|author2=Ouzts, Cynthia |year=2009|title=Tomographic Separation of Composite Spectra. XI. The Physical Properties of the Massive Close Binary HD 100213 (TU Muscae)|journal=The Astrophysical Journal|volume=681|issue=1 |pages=554–61|arxiv=0905.3687|doi=10.1086/587509|bibcode = 2008ApJ...681..554P |s2cid=16333964 }}</ref><!-- cites previous three sentences --> The system is thought to be around 4.8 kiloparsecs (~15500 light-years) distant.<ref name="terrell03">{{cite journal|last=Terrell|first=Dirk|author2=Munari, Ulisse |author3=Zwitter, Tomaˇz |author4= Nelson, Robert H.|date=2003|title=Observational Studies of Early-type Overcontact Binaries: TU Muscae|volume=126|issue=6|pages=2988–96|doi=10.1086/379678 |bibcode=2003AJ....126.2988T |journal=The Astronomical Journal|arxiv = astro-ph/0309366 |s2cid=6445980}}</ref><!-- cites previous two sentences -->

The period of the magnitude change is increasing, and has been calculated as lengthening by 3.46 seconds a century. This could be due to material from the less massive star being transferred to the more massive one, or there could be a third or fourth as yet undetected star in the multiple star system influencing the orbit. These stars have not been seen as they are much less luminous than the two main stars.<ref name="qian07">{{cite journal|display-authors=5|author=Qian, S.-B.|author2=Yuan, J.-Z.|author3=Liu, L.|author4=He, J.-J.|author5=Fernández Lajús, E.|author6=Kreiner, J. Z.|date=2007|title=Evolutionary states of the two shortest period O-type overcontact binaries V382 Cyg and TU Mus|journal=[[Monthly Notices of the Royal Astronomical Society]]|volume=380|issue=4|pages=1599–1607|doi=10.1111/j.1365-2966.2007.12184.x|doi-access=free |bibcode = 2007MNRAS.380.1599Q |hdl=11336/41984|s2cid=121158760 |url=http://sedici.unlp.edu.ar/handle/10915/93868|hdl-access=free}}</ref>

==Discovery== TU Muscae was discovered by Dutch astronomer [[Pieter Oosterhoff]] in 1928. Initially thought to have a spectrum of B3, later observations in the 1960s and early 1970s indicated it was a hotter star than previously thought—with the spectrum lying in the uncommon O-region.<ref name="andersen75">{{cite journal|last=Andersen|first=J.|author2=Grønbech, B.|date=1975|title=The close 0-type eclipsing binary TU Muscae|journal=Astronomy & Astrophysics|volume=45|pages=107–15|bibcode = 1975A&A....45..107A }}</ref>

==References== <references>

<ref name=MAST>{{cite web |title=MAST: Barbara A. Mikulski Archive for Space Telescopes |url=https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html |publisher=Space Telescope Science Institute |access-date=8 December 2021}}</ref>

</references>

{{Musca}}

[[Category:Beta Lyrae variables]] [[Category:Musca]] [[Category:O-type main-sequence stars]] [[Category:Spectroscopic binaries]] [[Category:Objects with variable star designations|Muscae, TU]] [[Category:Henry Draper Catalogue objects|100213]] [[Category:Hipparcos objects|056196]] [[Category:Durchmusterung objects]]