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Theta Muscae
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<h2 id="description">Description</h2> <p>Theta Muscae is a remote triple star system, the primary component of which is a carbon-sequence <a href="/facts/Wolf%E2%80%93Rayet_star/YxHnTsF5">Wolf–Rayet star</a>. This is a variety of highly-<a href="/facts/Luminosity/1tdhpk9l">luminous</a> hot <a href="/facts/Stellar_classification/dYrIuK9H">blue star</a> that has blown off its <a href="/facts/Stellar_structure/6bPfevnc">hydrogen envelope</a> and is emitting heavier elements, in this case <a href="/facts/Carbon/ukrgQexo">carbon</a>, amid a strong <a href="/facts/Stellar_wind/bn5J6vpx">stellar wind</a>. Theta Muscae is the second-brightest such star in the sky after <a href="/facts/Gamma_Velorum/twRat1rc">Gamma Velorum</a> in <a href="/facts/Vela_(constellation)/sRxGnXAE">Vela</a>. θ Mus is beyond the current reach of useful visual <a href="/facts/Parallax/Gu8W21LP">parallax</a> measurements, but has been estimated as around 7,400 <a href="/facts/Light-year/IGc5NdQb">light-years</a> (460 million <a href="/facts/Astronomical_unit/gjsbu5xU">astronomical units</a>) from <a href="/facts/Earth/HLLmDfj0">Earth</a>. While cataloging the stars in the far-southern sky, French explorer and astronomer <a href="/facts/Nicolas-Louis_de_Lacaille/zsd0KHzw">Nicolas-Louis de Lacaille</a> gave the star its <a href="/facts/Bayer_designation/KU2DVT47">Bayer designation</a> in 1756.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> </p> <h2 id="triple-system">Triple system</h2> <p>The <a href="/facts/Triple_star/1vX99BMV">triple star</a> θ Muscae A is composed of two parts: a spectroscopic <a href="/facts/Binary_system/9aRPc441">binary system</a> composed of the Wolf–Rayet star (spectral type: WC5 or 6) and an O-type <a href="/facts/Main_sequence/DJ3Wq8kd">main-sequence</a> star (spectral type: O6 or O7) that orbit each other every 19 days and a <a href="/facts/Blue_supergiant/8Bnl7Xpz">blue supergiant</a> (spectral type: O9.5/B0Iab) set about 46 milli<a href="/facts/Arcsecond/tybs6YGC">arcseconds</a> apart from them. If the system's estimated distance from Earth is accurate, the binary stars are about 0.5 <a href="/facts/Astronomical_unit/gjsbu5xU">AU</a> apart and the supergiant about 100 AU apart from them. Although the Wolf–Rayet star dominates the <a href="/facts/Astronomical_spectroscopy/NDGQ7mmM">spectrum</a>, it is visually only about a quarter of the brightness of the supergiant companion.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> All three are highly luminous: combined, they are likely to be over a million times as <a href="/facts/Luminosity/1tdhpk9l">luminous</a> as the Sun. The <a href="/facts/Stellar_wind/bn5J6vpx">stellar winds</a> of the Wolf–Rayet star and its close companion are so powerful that they form a <a href="/facts/Shock_wave/CqrG1Xm5">shock front</a> where they meet.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> The front produces <a href="/facts/X-ray/wseP79cN">X-rays</a>.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p> <h2 id="nebula">Nebula</h2> <p>A surrounding <a href="/facts/Emission_nebula/UzUTgCp8">emission nebula</a> is now thought to be a <a href="/facts/Supernova/Pfo2J23l">supernova</a> remnant, not directly connected to θ Muscae.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>C. de Loore; A.J. Willis (6 December 2012). Wolf-Rayet Stars: Observations, Physics, Evolution. Springer Science & Business Media. pp. 310–. ISBN 9789400979109. <a href="9789400979109" target="_blank">9789400979109</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Wagman, Morton (2003). Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others. Blacksburg, VA: The McDonald & Woodward Publishing Company. pp. 213–14. ISBN 978-0-939923-78-6. <a href="978-0-939923-78-6" target="_blank">978-0-939923-78-6</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Sugawara, Y.; Tsuboi, Y.; Maeda, Y. (2008). "Redshifted emission lines and radiative recombination continuum from the Wolf–Rayet binary θ Muscae: evidence for a triplet system?". Astronomy & Astrophysics. 490 (1): 259–64. arXiv:0810.1208. Bibcode:2008A&A...490..259S. doi:10.1051/0004-6361:20079302. S2CID 118447784. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Hill, G. M.; Moffat, A. F. J.; St-Louis, N. (2002). "Modelling the colliding-winds spectra of the 19-d WR + OB binary in the massive triple system Theta Muscae". Monthly Notices of the Royal Astronomical Society. 335 (4): 1069–78. Bibcode:2002MNRAS.335.1069H. doi:10.1046/j.1365-8711.2002.05694.x. <a href="https://doi.org/10.1046%2Fj.1365-8711.2002.05694.x" target="_blank">https://doi.org/10.1046%2Fj.1365-8711.2002.05694.x</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Stupar, M.; Parker, Q.A.; Filipovic, M.D. (2010). "The optical emission nebulae in the vicinity of WR 48 (Θ Mus); True Wolf–Rayet ejecta or unconnected supernova remnant?". Monthly Notices of the Royal Astronomical Society. 401 (3): 1760–69. arXiv:0910.1546. Bibcode:2010MNRAS.401.1760S. doi:10.1111/j.1365-2966.2009.15814.x. S2CID 119192064. <a href="https://doi.org/10.1111%2Fj.1365-2966.2009.15814.x" target="_blank">https://doi.org/10.1111%2Fj.1365-2966.2009.15814.x</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Stupar, M.; Parker, Q.A.; Filipovic, M.D. (2010). "The optical emission nebulae in the vicinity of WR 48 (Θ Mus); True Wolf–Rayet ejecta or unconnected supernova remnant?". Monthly Notices of the Royal Astronomical Society. 401 (3): 1760–69. arXiv:0910.1546. Bibcode:2010MNRAS.401.1760S. doi:10.1111/j.1365-2966.2009.15814.x. S2CID 119192064. <a href="https://doi.org/10.1111%2Fj.1365-2966.2009.15814.x" target="_blank">https://doi.org/10.1111%2Fj.1365-2966.2009.15814.x</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> </ol>