# TU Muscae

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Star in the constellation Musca

TU Muscae A light curve for TU Muscae, plotted from TESS data[1] Observation data Epoch J2000.0 Equinox J2000.0 Constellation Musca Right ascension 11h 31m 10.92470s[2] Declination −65° 44′ 32.1019″[2] Apparent magnitude (V) 8.307[3](8.17 - 8.75[4]) Characteristics Spectral type O7V + O8V[5] U−B color index −0.860[3] B−V color index +0.047[3] Variable type β Lyr[4] Astrometry Radial velocity (Rv) −4[6] km/s Proper motion (μ) RA: −6.62[2] mas/yr Dec.: −1.21[2] mas/yr Parallax (π) 0.02±0.76 mas[2] Orbit[5] Period (P) 1.387 days Semi-major axis (a) 17.34 R☉[7] Eccentricity (e) 0 Inclination (i) 77.7° Longitude of the node (Ω) 3.137[6]° Semi-amplitude (K1) (primary) 214.5 km/s Semi-amplitude (K2) (secondary) 345.8 km/s Details[5] Primary Mass 16.8 M☉ Radius 7.2 R☉ Luminosity 105,000 L☉ Surface gravity (log g) 4.05[7] cgs Temperature 35,000[6] K secondary Mass 10.5 M☉ Radius 5.7 R☉ Luminosity 35,000 L☉ Surface gravity (log g) 4.04[7] cgs Temperature 31,366[6] K Other designations TU Muscae, HIP 56196, HD 100213, BD−65°1101, 2MASS J11311091-6544322 Database references SIMBAD data

**TU Muscae**, also known as **HD 100213**, is an [eclipsing binary](/source/Eclipsing_binary) [star](/source/Star) in the [constellation](/source/Constellation) [Musca](/source/Musca). Its [apparent magnitude](/source/Apparent_magnitude) ranges from 8.17 to 8.75 over around 1.4 days.[4]

## Physical description

TU Muscae is a remote [binary star](/source/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 ([overcontact binary](/source/Contact_binary)) and are classed as a [Beta Lyrae variable](/source/Beta_Lyrae_variable) as their light varies from earth as they eclipse each other.[6] 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](/source/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](/source/Roche_lobe) overflow. However they concede that figuring out the evolution of interacting massive binary systems is "a little like trying to unspill milk".[5] The system is thought to be around 4.8 kiloparsecs (~15500 light-years) distant.[6]

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.[8]

## Discovery

TU Muscae was discovered by Dutch astronomer [Pieter Oosterhoff](/source/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.[9]

## References

1. **[^](#cite_ref-MAST_1-0)** ["MAST: Barbara A. Mikulski Archive for Space Telescopes"](https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html). Space Telescope Science Institute. Retrieved 8 December 2021.

1. ^ [***a***](#cite_ref-hipparcos_2-0) [***b***](#cite_ref-hipparcos_2-1) [***c***](#cite_ref-hipparcos_2-2) [***d***](#cite_ref-hipparcos_2-3) [***e***](#cite_ref-hipparcos_2-4) Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". *Astronomy and Astrophysics*. **474** (2): 653–664. [arXiv](/source/ArXiv_(identifier)):[0708.1752](https://arxiv.org/abs/0708.1752). [Bibcode](/source/Bibcode_(identifier)):[2007A&A...474..653V](https://ui.adsabs.harvard.edu/abs/2007A&A...474..653V). [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20078357](https://doi.org/10.1051%2F0004-6361%3A20078357). [S2CID](/source/S2CID_(identifier)) [18759600](https://api.semanticscholar.org/CorpusID:18759600).

1. ^ [***a***](#cite_ref-ubv_3-0) [***b***](#cite_ref-ubv_3-1) [***c***](#cite_ref-ubv_3-2) Maíz-Apellániz, Jesús; [Walborn, Nolan R.](/source/Nolan_R._Walborn); Galué, Héctor Á.; Wei, Lisa H. (2004). "A Galactic O Star Catalog". *The Astrophysical Journal Supplement Series*. **151** (1): 103–148. [arXiv](/source/ArXiv_(identifier)):[astro-ph/0311196](https://arxiv.org/abs/astro-ph/0311196). [Bibcode](/source/Bibcode_(identifier)):[2004ApJS..151..103M](https://ui.adsabs.harvard.edu/abs/2004ApJS..151..103M). [doi](/source/Doi_(identifier)):[10.1086/381380](https://doi.org/10.1086%2F381380). [S2CID](/source/S2CID_(identifier)) [118813863](https://api.semanticscholar.org/CorpusID:118813863).

1. ^ [***a***](#cite_ref-gcvs_4-0) [***b***](#cite_ref-gcvs_4-1) [***c***](#cite_ref-gcvs_4-2) Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". *VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S*. **1**. [Bibcode](/source/Bibcode_(identifier)):[2009yCat....102025S](https://ui.adsabs.harvard.edu/abs/2009yCat....102025S).

1. ^ [***a***](#cite_ref-penny08_5-0) [***b***](#cite_ref-penny08_5-1) [***c***](#cite_ref-penny08_5-2) [***d***](#cite_ref-penny08_5-3) Penny, Laura R.; Ouzts, Cynthia (2009). "Tomographic Separation of Composite Spectra. XI. The Physical Properties of the Massive Close Binary HD 100213 (TU Muscae)". *The Astrophysical Journal*. **681** (1): 554–61. [arXiv](/source/ArXiv_(identifier)):[0905.3687](https://arxiv.org/abs/0905.3687). [Bibcode](/source/Bibcode_(identifier)):[2008ApJ...681..554P](https://ui.adsabs.harvard.edu/abs/2008ApJ...681..554P). [doi](/source/Doi_(identifier)):[10.1086/587509](https://doi.org/10.1086%2F587509). [S2CID](/source/S2CID_(identifier)) [16333964](https://api.semanticscholar.org/CorpusID:16333964).

1. ^ [***a***](#cite_ref-terrell03_6-0) [***b***](#cite_ref-terrell03_6-1) [***c***](#cite_ref-terrell03_6-2) [***d***](#cite_ref-terrell03_6-3) [***e***](#cite_ref-terrell03_6-4) [***f***](#cite_ref-terrell03_6-5) Terrell, Dirk; Munari, Ulisse; Zwitter, Tomaˇz; Nelson, Robert H. (2003). "Observational Studies of Early-type Overcontact Binaries: TU Muscae". *The Astronomical Journal*. **126** (6): 2988–96. [arXiv](/source/ArXiv_(identifier)):[astro-ph/0309366](https://arxiv.org/abs/astro-ph/0309366). [Bibcode](/source/Bibcode_(identifier)):[2003AJ....126.2988T](https://ui.adsabs.harvard.edu/abs/2003AJ....126.2988T). [doi](/source/Doi_(identifier)):[10.1086/379678](https://doi.org/10.1086%2F379678). [S2CID](/source/S2CID_(identifier)) [6445980](https://api.semanticscholar.org/CorpusID:6445980).

1. ^ [***a***](#cite_ref-palate_7-0) [***b***](#cite_ref-palate_7-1) [***c***](#cite_ref-palate_7-2) Palate, M.; Rauw, G. (2012). "Spectral modelling of circular massive binary systems. Towards an understanding of the Struve-Sahade effect?". *Astronomy & Astrophysics*. **537**: A119. [arXiv](/source/ArXiv_(identifier)):[1109.1103](https://arxiv.org/abs/1109.1103). [Bibcode](/source/Bibcode_(identifier)):[2012A&A...537A.119P](https://ui.adsabs.harvard.edu/abs/2012A&A...537A.119P). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201117520](https://doi.org/10.1051%2F0004-6361%2F201117520). [S2CID](/source/S2CID_(identifier)) [84840295](https://api.semanticscholar.org/CorpusID:84840295).

1. **[^](#cite_ref-qian07_8-0)** Qian, S.-B.; Yuan, J.-Z.; Liu, L.; He, J.-J.; Fernández Lajús, E.; et al. (2007). ["Evolutionary states of the two shortest period O-type overcontact binaries V382 Cyg and TU Mus"](http://sedici.unlp.edu.ar/handle/10915/93868). *[Monthly Notices of the Royal Astronomical Society](/source/Monthly_Notices_of_the_Royal_Astronomical_Society)*. **380** (4): 1599–1607. [Bibcode](/source/Bibcode_(identifier)):[2007MNRAS.380.1599Q](https://ui.adsabs.harvard.edu/abs/2007MNRAS.380.1599Q). [doi](/source/Doi_(identifier)):[10.1111/j.1365-2966.2007.12184.x](https://doi.org/10.1111%2Fj.1365-2966.2007.12184.x). [hdl](/source/Hdl_(identifier)):[11336/41984](https://hdl.handle.net/11336%2F41984). [S2CID](/source/S2CID_(identifier)) [121158760](https://api.semanticscholar.org/CorpusID:121158760).

1. **[^](#cite_ref-andersen75_9-0)** Andersen, J.; Grønbech, B. (1975). "The close 0-type eclipsing binary TU Muscae". *Astronomy & Astrophysics*. **45**: 107–15. [Bibcode](/source/Bibcode_(identifier)):[1975A&A....45..107A](https://ui.adsabs.harvard.edu/abs/1975A&A....45..107A).

v t e Constellation of Musca List of stars in Musca Musca in Chinese astronomy Stars Bayer α β γ δ ε ζ1 ζ2 η θ ι1 ι2 λ μ λ Cha Variable R S SY TU GQ GR GU GT KR MP V357 HR 4538 4549 5002 HD 111232 112410 Other Gliese 440 PSR J1141−6545 YSES 1 YSES 2 YSES 2b Exoplanets HD 111232 b Star clusters NGC 4372 NGC 4463 NGC 4815 NGC 4833 Nebulae NGC 5189 Other BHR 71 Dark Doodad Nebula Engraved Hourglass Nebula G299.2-2.9 Category

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Adapted from the Wikipedia article [TU Muscae](https://en.wikipedia.org/wiki/TU_Muscae) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/TU_Muscae?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.