Editing Musca (section)

== Features ==

===Stars===
{{see also|List of stars in Musca}}
[[Image:Constellation Musca.jpg|thumb|left|upright|Musca as seen by the naked eye]]
Lacaille charted and designated 10 stars with the [[Bayer designation]]s Alpha to Kappa in 1756. He catalogued stars that became [[Lambda Muscae|Lambda]] and [[Mu Muscae|Mu]], but did not designate them as he considered them ''informes'' as they lay outside the asterism proper. [[Francis Baily]] considered them part of Musca, and Gould gave them their Bayer designations. Baily also dropped Kappa, which he felt was too faint to warrant a name, and designated two adjacent stars as [[Zeta1 Muscae|Zeta<sup>1</sup>]] and [[Zeta2 Muscae|Zeta<sup>2</sup>]]. These last two stars are 1° apart, quite far to be sharing a Bayer designation. Lacaille had originally labelled the fainter one as Zeta, while Baily presupposed he had meant to label the brighter one. Reluctant to remove Lacaille's designation, he gave them both the Zeta designation.<ref name=wagman>{{cite book  | last = Wagman  | first = Morton  | date = 2003  | title = Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others  | publisher = The McDonald & Woodward Publishing Company  | location = Blacksburg, Virginia  | isbn = 978-0-939923-78-6 |pages=213–14}}</ref><!-- cites seven previous sentences --> Altogether there are 62 stars brighter than magnitude 6.5 in the constellation.<ref name=tirionconst/>

The pattern of the brightest stars resembles that of [[Ursa Minor]], in that the stars form a pattern reminiscent of a bowl with a handle.<ref name=bagnall/> Lying south-southeast of [[Acrux]] in neighbouring Crux is [[Alpha Muscae]].<ref name="motz">{{cite book|last=Motz|first=Lloyd|author2=Nathanson, Carol|title=The Constellations: An Enthusiast's Guide to the Night Sky|publisher=Aurum Press|location=London, United Kingdom|date=1991|pages=385–86|isbn=978-1-85410-088-7}}</ref> It is the brightest star in the constellation with an [[apparent magnitude]] of 2.7. Lying around 310 [[light-year]]s away, it is a blue-white star of [[Stellar classification#Spectral types|spectral type]] B2IV-V that is around 4520 times as [[luminosity|luminous]] and 8 times as massive as the [[Sun]]. The star is a [[Beta Cephei variable]] with about 4.7 times the Sun's diameter, and pulsates every 2.2&nbsp;hours, varying by 1% in brightness. A nearby star of magnitude&nbsp;13 may or may not be a companion star.<ref name="kaleralpha">{{cite web|url=http://stars.astro.illinois.edu/sow/alphamus.html |title=Alpha Muscae |last=Kaler|first=Jim|author-link= James B. Kaler |work=Stars|publisher=University of Illinois|access-date=21 December 2013}}</ref><!-- cites four previous sentences --> Marking the fly's tail is Gamma Muscae,<ref name="motz"/> a blue-white star of spectral type B5V that varies between magnitudes 3.84 and 3.86 over a period of 2.7&nbsp;days. It is a variable of a different type, classed as a [[slowly pulsating B star]], a type of variable.<ref name=AAVSOgam>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=19956 |title=Gamma Muscae |author=Otero, Sebastian Alberto |date=5 March 2012|work=AAVSO Website|publisher=American Association of Variable Star Observers|access-date=21 December 2013}}</ref> <!-- cites previous 1.5 sentences --> It is around five times as massive as the Sun.<ref>{{cite journal|author =Molenda-Zakowicz, J. |author2 =Połubek, G.|date=2004|title=Empirical Absolute Magnitudes, Luminosities and Effective Temperatures of SPB Variables and the Problem of Variability Classification of Monoperiodic Stars|journal=Acta Astronomica|volume=54|pages=281–97 [283]|url=http://acta.astrouw.edu.pl/Vol54/n3/pap_54_3_4.pdf|bibcode = 2004AcA....54..281M }}</ref>

Beta Muscae is a [[binary star]] system around&nbsp;341 light-years distant that is composed of two [[B-type main-sequence star|blue-white main-sequence stars]] of spectral types B2V and B3V that orbit each other every 194&nbsp;years. They are eight and six times as massive as the Sun, respectively, and have about 3.5&nbsp;times its diameter.<ref name="kalerbeta">{{cite web|url=http://stars.astro.illinois.edu/sow/betamus.html |title=Beta Muscae |last=Kaler|first=Jim|author-link= James B. Kaler |work=Stars|publisher=University of Illinois|date=22 June 2010| access-date=23 December 2013}}</ref> Zeta<sup>2</sup> Muscae is a [[A-type main-sequence star|white main sequence star]] of spectral type A5V around 330&nbsp;light-years distant from Earth.<ref>{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=zeta2+mus&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = HR 4703 – Star in Double System |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 25 December 2013}}</ref> It is part of a triple star system with faint companions at 0.5 and 32.4&nbsp;arc seconds distance.<ref name="chen12">{{cite journal|author=Chen, Christine H. |display-authors=4  |author2=Pecaut, Mark |author3=Mamajek, Eric E. |author4=Su, Kate Y. L. |author5=Bitner, Martin |date=2012|title=A Spitzer MIPS Study of {{Solar mass|2.5–2.0}} Stars in Scorpius-Centaurus|journal=The Astrophysical Journal|volume=756|issue=2|pages=133–57|arxiv=1207.3415|doi=10.1088/0004-637x/756/2/133|bibcode = 2012ApJ...756..133C |s2cid=119278056 }}</ref> [[Eta Muscae]] is a multiple star system, the two main components forming an eclipsing binary that has a combined spectral type of B8V and magnitude of 4.77 that dips by 0.05&nbsp;magnitude every 2.39&nbsp;days.<ref name="Zasche09">{{cite journal|author=Zasche, P. |display-authors=4  |author2=Wolf, M. |author3=Hartkopf, W. I. |author4=Svoboda, P. |author5=Uhlař, R. |author6=Liakos, A. |author7=Gazeas, K.|date=2009|title=A Catalog of Visual Double and Multiple Stars with Eclipsing Components|journal=The Astronomical Journal|volume=138|issue=2|pages=664–79|doi=10.1088/0004-6256/138/2/664|arxiv = 0907.5172 |bibcode = 2009AJ....138..664Z |s2cid=17089387 }}</ref> Alpha, Beta, Gamma, [[HD 103079]], Zeta<sup>2</sup> and (likely) Eta are all members of the Lower Centaurus Crux subgroup of the [[Scorpius–Centaurus association]], a group of predominantly hot blue-white stars that share a common origin and [[proper motion]] across the galaxy.<ref name=dezeeuw99>{{cite journal|title=A Hipparcos Census of Nearby OB Associations|author=de Zeeuw, P.T. |display-authors=4  |author2=Hoogerwerf, R. |author3=de Bruijne, J.H.J. |author4=Brown, A.G.A. |author5=Blaauw, A.|date=1999|journal=Astronomical Journal|volume=117|issue=1|pages=354–99|bibcode=1999AJ....117..354D|doi=10.1086/300682|arxiv = astro-ph/9809227 |s2cid=16098861 }}</ref><ref name=aaa216_1_44>{{citation | last1=de Geus | first1=E. J. | last2=de Zeeuw | first2=P. T. | last3=Lub | first3=J. | title=Physical Parameters of Stars in the Scorpio-Centaurus OB Association | journal=Astronomy and Astrophysics | volume=216 | issue=1–2 | pages=44–61 |date=June 1989 | bibcode=1989A&A...216...44D }}</ref>

Delta and Epsilon mark the fly's left wing and right wing, respectively.<ref name="motz"/> With an apparent magnitude of 3.62, Delta is an orange giant of spectral type K2III located around 91&nbsp;light-years away.<ref>{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=del+Mus |title = Delta Muscae |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 25 December 2013}}</ref> [[Epsilon Muscae]] is a [[red giant]] of spectral type M5III and semiregular variable that ranges between magnitudes 3.99 and 4.31 over approximately 40&nbsp;days.<ref name=AAVSOeps>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=19957 |title=Epsilon Muscae |author=Watson, Christopher |date=25 August 2009|work=AAVSO Website|publisher=American Association of Variable Star Observers|access-date=21 December 2013}}</ref> It has expanded to 130 times the Sun's diameter and 1800 to 2300 its luminosity. It was a star originally 1.5 to 2&nbsp;times as massive as the Sun. Although of a similar distance—around 302 light-years—to the stars of the Lower Centaurus Crux subgroup, it is moving much faster at around 100&nbsp;km/s and does not share a common origin.<ref name="kalereps">{{cite web|url=http://stars.astro.illinois.edu/sow/epsmus.html |title=Epsilon Muscae |last=Kaler|first=Jim|author-link= James B. Kaler |work=Stars|publisher=University of Illinois|access-date=21 December 2013}}</ref><!-- cites previous three sentences --> To the northwest lies Mu Muscae, an orange giant of spectral type K4III that varies between apparent magnitude 4.71 and 4.76, and has been classified as a slow, irregular variable.<ref name=AAVSOmu>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=19960 |title=Mu Muscae |author=Otero, Sebastian Alberto |date=31 October 2011|work=AAVSO Website|publisher=American Association of Variable Star Observers|access-date=21 January 2014}}</ref> Near Mu is Lambda Muscae, the third-brightest star in the constellation and a white main-sequence star of spectral type A7V around 128&nbsp;light-years distant from Earth.<ref>{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?submit=display&bibdisplay=refsum&bibyear1=2009&bibyear2=2014&Ident=%403269938&Name=*+lam+Mus#lab_bib |title = Lambda Muscae – Star in Double System |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 25 December 2013}}</ref>

Located near Alpha is [[R Muscae]],<ref name="motz"/> a [[classical Cepheid variable]] ranging from apparent magnitude 5.93 to 6.73 over 7.5&nbsp;days. It is a yellow-white supergiant ranging between spectral types F7Ib and G2Ib,<ref name=AAVSOR>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=19677 |title=R Muscae |author=Watson, Christopher |date=4 January 2010|work=AAVSO Website|publisher=American Association of Variable Star Observers|access-date=21 December 2013}}</ref> located around 2037&nbsp;light-years away.<ref>{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=R+Muscae&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = R Muscae – Classical Cepheid (delta Cephei type) |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 21 December 2013}}</ref> [[S Muscae]] is likewise a classical Cepheid, a yellow-white supergiant ranging between spectral types F6Ib and G0Ib and magnitudes 5.89 to 6.49 over a period of 9.66&nbsp;days.<ref name=AAVSOS>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=19678 |title=S Muscae | author=Watson, Christopher |date=4 January 2010|work=AAVSO Website|publisher=American Association of Variable Star Observers|access-date=21 December 2013}}</ref> A luminous star around 5.9&nbsp;times as massive as the Sun, it is a binary star with a blue-white main-sequence star companion likely to be of spectral type B3V to B5V with a mass of just over 5&nbsp;solar masses,<ref name="bohm97">{{cite journal|author=Böhm-Vitense, Erika |display-authors=4  |author2=Evans, Nancy Remage |author3=Carpenter, Kenneth |author4=Beck-Winchatz, Bernhard |author5=Robinson, Richard|date=1997|title=The Mass of the Classical Cepheid S Muscae|journal=The Astrophysical Journal|volume=477|issue=2 |pages=916–25|bibcode = 1997ApJ...477..916B|doi=10.1086/303725|doi-access=free}}</ref> one of the hottest and brightest companions of a cepheid known. The two stars orbit each other every 505&nbsp;days.<ref>{{cite journal|last=Evans|first=Nancy Remage|date=1990|title=The orbit and colors of the Cepheid S Muscae|journal= Publications of the Astronomical Society of the Pacific |volume=102|pages= 551–57|bibcode=1990PASP..102..551E|doi=10.1086/132668|doi-access=free}}</ref><!-- cites previous 1.5 sentences -->

[[Theta Muscae]] is a triple star system thought to be around 7,500&nbsp;light-years distant.<ref name="kalertheta">{{cite web|url=http://stars.astro.illinois.edu/sow/thetamus.html |title=Theta Muscae |last=Kaler|first=Jim|author-link= James B. Kaler |work=Stars|publisher=University of Illinois|access-date=21 November 2013}}</ref> It consists of a [[spectroscopic binary]] system composed of the [[Wolf–Rayet star]] (spectral type: WC5 or 6) and an [[O-type main-sequence star]] (spectral type: O6 or O7) that orbit each other every 19 days and a [[blue supergiant]] (spectral type: O9.5/B0Iab) set about 46&nbsp;[[Minute of arc|milliarcseconds]] apart from them. If the system's estimated distance from Earth is accurate, the binary stars are about 0.5&nbsp;[[astronomical unit]]s (AU) apart and the supergiant about 100&nbsp;AU apart from them.<ref name=sugawara08>{{cite journal|author=Sugawara, Y. |author2=Tsuboi, Y. |author3=Maeda, Y.|date=2008|title=Redshifted Emission Lines and Radiative Recombination Continuum from the Wolf–Rayet Binary θ Muscae: Evidence for a Triplet System?|journal=[[Astronomy & Astrophysics]]|volume=490|issue=1 |pages=259–64|url=http://www.aanda.org/articles/aa/pdf/2008/40/aa9302-07.pdf|doi=10.1051/0004-6361:20079302|arxiv = 0810.1208 |bibcode = 2008A&A...490..259S |s2cid=118447784 }}</ref> All three are highly luminous; combined, they are likely to be over a million times as luminous as the Sun.<ref name="kalertheta"/> [[TU Muscae]] is a binary star system located around 15,500&nbsp;light-years away made up of two hot, luminous, blue main-sequence stars of spectral types O7.5V and O9.5V,<ref name="terrell03"/><ref name=sbtu>{{cite web |url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=TU+Muscae&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title=TU Muscae – Eclipsing Binary of Beta Lyrae type (semi-detached) |work=[[SIMBAD|SIMBAD Astronomical Database]] |publisher=Centre de Données astronomiques de Strasbourg |access-date=28 December 2013}}</ref> with masses 23 and 15&nbsp;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">{{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|journal=The Astronomical Journal|volume=126|issue=6|pages=2988–96|arxiv=astro-ph/0309366|bibcode = 2003AJ....126.2988T |doi = 10.1086/379678 |s2cid=6445980}}</ref> The system ranges from apparent magnitude 8.17 to 8.75 over around 1.4&nbsp;days.<ref name=AAVSOTU>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=19704 |title=TU Muscae |author=Watson, Christopher |date=4 January 2010|work=AAVSO Website|publisher=American Association of Variable Star Observers|access-date=28 December 2013}}</ref>

Also known as Nova Muscae 1983, [[GQ Muscae]] is a binary system consisting of a white dwarf and small star that is about 10% as massive as the Sun. The two orbit each other every 1.4&nbsp;hours. The white dwarf accumulates material from its companion star via its [[accretion disc]]. After a certain amount has accumulated, the star erupts, as it did in 1983, reaching a magnitude of 7.2.<ref>{{cite journal|author=Hachisu, Izumi |author2=Kato, Mariko |author3=Cassatella, Angelo  |date=2008|title=A Universal Decline Law of Classical Novae. III. GQ Muscae 1983|journal=The Astrophysical Journal|volume=687|issue=2 |pages=1236–52|bibcode=2008ApJ...687.1236H|doi=10.1086/591415|arxiv = 0806.4253 |s2cid=50476380 }}</ref> Discovered with a magnitude of 7.1 on 18 January 1983,<ref name=liller90>{{cite book|last=Liller|first=William|title=Cambridge Astronomy Guide|publisher=CUP Archive|location=Cambridge, United Kingdom|date=1990|page=105|isbn=0-521-39915-7|url=https://books.google.com/books?id=yl04AAAAIAAJ&pg=PA105}}</ref> it was the first nova from which X-rays were detected.<ref name="duerbeck">{{cite journal|last=Duerbeck|first=H.W.|date=2009|title=New Stars and Telescopes: Nova Research in the Last Four Centuries|journal=Astronomische Nachrichten|volume=330|issue=6|pages=568–73|url=http://www.physics.usyd.edu.au/~laszlo/kepek/400ev_novai.pdf|doi=10.1002/asna.200911218|bibcode=2009AN....330..568D|url-status=dead|archive-url=https://web.archive.org/web/20150924073139/http://www.physics.usyd.edu.au/~laszlo/kepek/400ev_novai.pdf|archive-date=2015-09-24}}</ref> The [[soft X-ray transient]] [[GRS 1124-683]] (also known as Nova Muscae 1991) is a binary object consisting of an orange main-sequence star (GU Muscae) of spectral type K3V–K4V and a [[black hole]] of around six solar masses.<ref name="kreidberg12">{{cite journal|last=Kreidberg|first=Laura|author2=Bailyn, Charles D. |author3=Farr, Will M. |author4= Kalogera, Vicky  |date=2012|title=Mass Measurements of Black Holes in X-ray Transients: is There a Mass Gap? |journal=The Astrophysical Journal|volume=757|issue=36|pages=17|bibcode=2012ApJ...757...36K|doi=10.1088/0004-637x/757/1/36|arxiv = 1205.1805 |s2cid=118452794}}</ref> During the 1991 outburst which led to its discovery, [[radiation]] was produced through a process of [[positron]] [[annihilation]].<ref name=Sunyaev>{{cite journal |date=1992 |author=Sunyaev, R. |display-authors=4 |author2=Churazov, E. |author3=Gilfanov, M. |author4=Dyachkov, A. |author5=Khavenson, N. |author6=Grebenev, S. |author7=Kremnev, R. |author8=Sukhanov, K. |author9=Goldwurm, A. |author10=Ballet, J. |author11=Cordier, B. |author12=Paul, J. |author13=Denis, M. |author14=Vedrenne, G. |author15=Niel, M. |author16=Jourdain, E. |title=X-ray Nova in Musca (GRS 1124+68): Hard X-ray Source with Narrow Annihilation Line |journal=Astrophysical Journal Letters |volume=389 |issue=2 |pages=L75-78 |bibcode=1992ApJ...389L..75S |doi=10.1086/186352 |doi-access=free }}</ref> [[GR Muscae]] is an X-ray source composed of a [[neutron star]] of between 1.2 and 1.8 times the mass of the Sun and a low-mass star likely to be around the mass of the Sun in close orbit.<ref name="Cornelisse2013">{{cite journal|author=Cornelisse, R. |display-authors=4  |author2=Kotze, M.M. |author3=Casares, J. |author4=Charles, P.A. |author5=Hakala, P.J.|date=2013|title=The Origin of the Tilted Disc in the Low-mass X-ray Binary GR Mus (XB 1254-690)|journal=Monthly Notices of the Royal Astronomical Society|volume=436|issue=1|pages=910–20|arxiv=1309.4972|doi=10.1093/mnras/stt1654|doi-access=free |bibcode = 2013MNRAS.436..910C |s2cid=119242800 }}</ref> Finally, [[SY Muscae]] is a [[symbiotic nova|symbiotic]] star system composed of a red giant and white dwarf, where although the larger star is transferring mass to the smaller,  no periodic eruption occurs nor does an accretion disc form.<ref name="schmutz94">{{cite journal |title = High resolution spectroscopy of symbiotic stars I. SY Muscae: orbital elements, M giant radius, distance |author = Schmutz, W. |author2 =Schild, H. |author3 =Muerset, U. |author4 =Schmid, H.M. |journal = Astronomy and Astrophysics |volume=288 |pages = 819–28 |date=1994 |bibcode = 1994A&A...288..819S }}</ref> The star system varies in magnitude from 10.2 to 12.7 over a period of 624.5 days.<ref name=AAVSOSY>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=19701 |title=SY Muscae |author=Otero, Sebastian Alberto|date=13 March 2013|work=AAVSO Website|publisher=American Association of Variable Star Observers|access-date=11 March 2014}}</ref> V415 Muscae is a nova that had an outburst in 8 June 2022 with an apparent magnitude of +8.7.<ref>{{Cite web |title=ATel #15435: Spectroscopic monitoring of bright Galactic nova ASASSN-22hw |url=https://www.astronomerstelegram.org/?read=15435 |access-date=2022-06-30 |website=ATel}}</ref>

[[File:Coalsack and Dark Doodad Dark Nebulae.jpg|thumb|right|upright|The [[Coalsack Nebula]] can be seen as the large, dark region near the top of the photo. It extends into the northeast of Musca. The vertical dark column in the lower right of the image is the [[Dark Doodad Nebula]].]]

Three star systems have been discovered to have [[exoplanets]]. [[HD 111232]] is a yellow main-sequence star around 78% as massive as the Sun around 95&nbsp;light-years distant. It has a planet ([[HD 111232 b]]) around 6.8&nbsp;times the mass of [[Jupiter]] that has an orbital period around 1143 days.<ref name="Mayor2004">{{cite journal | title=The CORALIE Survey for Southern Extra-solar Planets XII. Orbital Solutions for 16 Extra-solar Planets Discovered with CORALIE  | display-authors=4  | last1=Mayor | first1=M. | last2=Udry | first2=S. | last3=Naef | first3=D. | last4=Pepe | first4=F. | last5=Queloz | first5=D. | last6=Santos | first6=N. C. | last7=Burnet | first7=M. | journal=Astronomy & Astrophysics | volume=415 | issue=1 | pages=391–402 | date=2004 | arxiv=astro-ph/0310316 | bibcode=2004A&A...415..391M | doi=10.1051/0004-6361:20034250 | s2cid=5233877 }}</ref> [[HD 112410]] is a yellow giant of spectral type G8III located around 439&nbsp;light-years distant.<ref>{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+112410&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = HD 112410 – Red Giant Branch star |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 26 December 2013}}</ref> With around 1.54&nbsp;times the mass of the Sun, it is cooling and expanding along the [[Stellar evolution#Red-giant-branch phase|red-giant branch]], having left the [[main sequence]] after exhausting its core supply of hydrogen fuel. It has a substellar companion calculated to have a mass 9.2&nbsp;times that of Jupiter and an orbital period of 124.6&nbsp;days at a distance around 0.57 AU.<ref name="jones13">{{cite journal|author=Jones, M.I. |display-authors=4  |author2=Jenkins, J.S. |author3=Rojo, P. |author4=Melo, C. H. F. |author5=Bluhm, Paz |date=2013|title=Study of the Impact of the Post-MS evolution of the Host Star on the Orbits of Close-in Planets. II. A Giant Planet in a Close-in Orbit around the RGB Star HIP 63242|journal=Astronomy & Astrophysics|volume=556|issue=A78|pages=5|doi=10.1051/0004-6361/201321660|arxiv = 1306.3939 |bibcode = 2013A&A...556A..78J |s2cid=118618692 }}</ref> Yet another member of the Lower Centaurus Crux subgroup,<ref name=dezeeuw99/> [[HD 100546]] is a young, blue-white [[Herbig Ae/Be star]] of spectral type B9V that has yet to settle on the main sequence—the closest of these stars to Earth around 320&nbsp;light-years distant.<ref name="quanz13"/><ref name="Grady2001">{{Cite journal | title=The Disk and Environment of the Herbig Be Star HD 100546 | display-authors=4 | last1=Grady | first1=C. A.| last2=Polomski | first2=E. F. | last3=Henning | first3=Th. | last4=Stecklum | first4=B. | last5=Woodgate | first5=B. E. | last6=Telesco | first6=C. M. | last7=Piña | first7=R. K. | last8=Gull | first8=T. R. | last9=Boggess | first9=A. | last10=Bowers | first10=C. W. | last11=Bruhweiler | first11=F. C. | last12=Clampin | first12=M. | last13=Danks | first13=A. C. | last14=Green | first14=R. F. | last15=Heap | first15=S. R. | last16=Hutchings | first16=J. B. | last17=Jenkins | first17=E. B. | last18=Joseph | first18=C. | last19=Kaiser | first19=M. E. | last20=Kimble | first20=R. A. | last21=Kraemer | first21=S. | last22=Lindler | first22=D. | last23=Linsky | first23=J. L. | last24=Maran | first24=S. P. | last25=Moos | first25=H. W. | last26=Plait | first26=P. | last27=Roesler | first27=F. | last28=Timothy | first28=J. G. | last29=Weistrop | first29=D.|date=2001 | journal=The Astronomical Journal | volume=122 | issue=6 | pages=3396–3406 | bibcode=2001AJ....122.3396G | doi=10.1086/324447 | doi-access=free }}</ref><!-- cites closest --> It is surrounded by a circumstellar debris disk from a distance of 0.2 to 4&nbsp;AU, and again from 13&nbsp;AU out to a few hundred AU, with evidence for a protoplanet forming at a distance around 47&nbsp;AU.<ref name="quanz13">{{cite journal|author=Quanz, Sasch P. |display-authors=4  |author2=Amara, Adam |author3=Meyer, Michael P. |author4=Kenworthy, Matthew P. |author5=Kasper, Markus |author6=Girard, Julien H.|date=2013|title=A Young Protoplanet Candidate Embedded in the Circumstellar Disk of HD 100546|journal= Astrophysical Journal|volume=766|issue=1 |pages=L1–L6|doi=10.1088/2041-8205/766/1/l1|arxiv = 1302.7122 |bibcode = 2013ApJ...766L...1Q |s2cid=56140977 }}</ref> A gap exists between 4 and 13&nbsp;AU, which appears to contain a large planet around 20&nbsp;times the mass of Jupiter,<ref name=planet-1>{{Cite journal | title = Resolving the Disk Rotation of HD 97048 and HD 100546 in the <nowiki>[O I]</nowiki> 6300A Line: Evidence for a Giant Planet Orbiting HD 100546 | last1 = Acke | first1 = B. | last2 = van der Ancker | first2 = M. | journal = Astronomy & Astrophysics | date = 2005 | volume = 449 | issue = 267 | arxiv = astro-ph/0512562|doi = 10.1051/0004-6361:20054330 | bibcode=2006A&A...449..267A | pages = 267| s2cid = 10148216 }}</ref> although further examination of the disk profile indicates it might be a more massive object such as a [[brown dwarf]] or more than one planet.<ref>{{cite journal|author=Mulders, Gijs D. |display-authors=4  |author2=Paardekooper, Sijme-Jan |author3=Pani'c, Olja |author4=Dominik, Carsten |author5=van Boekel, Roy |author6=Ratzka, Thorsten|date=2013|title=Planet or Brown Dwarf? Inferring the Companion Mass in HD 100546 from the Wall Shape using Mid-Infrared Interferometry|journal=Astronomy & Astrophysics|volume=557A|bibcode=2013A&A...557A..68M|arxiv=1306.4264|pages=10|issue=A68|doi = 10.1051/0004-6361/201220930 |s2cid=9014058 }}</ref> [[LP 145-141]] is a white dwarf located 15&nbsp;light-years distant—the fourth-closest to the [[Solar System]].<ref>{{cite journal|title= The White Dwarfs Within 20 Parsecs of the Sun: Kinematics and Statistics | author=Sion, Edward M. |display-authors=4  | author2=Holberg, Jay B. | author3=Oswalt, T.D. | author4=McCook, G.P. | author5=Wasatonic, R.| journal= The Astronomical Journal | volume=138 |issue=6 |date=2009| pages=1681–89 [Table 1] | doi=10.1088/0004-6256/138/6/1681| bibcode=2009AJ....138.1681S |arxiv = 0910.1288 | s2cid=119284418 }}</ref> It is considered a good candidate to look for Jupiter-like planets, on account if its proximity and mass.<ref name="burleigh02">{{cite journal|author=Burleigh, Matthew R. |author2=Clarke, F.J. |author3=Hodgkin, S.T.  |date=2002|title=Imaging Planets around Nearby White Dwarfs|journal=Monthly Notices of the Royal Astronomical Society|volume=331|issue=4|pages=L41–L45|bibcode=2002MNRAS.331L..41B|doi=10.1046/j.1365-8711.2002.05417.x|doi-access=free |arxiv = astro-ph/0202194 |s2cid=18383063 }}</ref>

===Deep-sky objects===
Located on the border with Circinus is the unusual [[planetary nebula]] [[NGC 5189]],<ref name="streicher"/> estimated to be around 1750&nbsp;light-years away from Earth.<ref name=sbngc5189>{{cite web |url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=NGC+5189&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title=NGC 5189 – Planetary Nebula |work=[[SIMBAD|SIMBAD Astronomical Database]] |publisher=Centre de Données astronomiques de Strasbourg |access-date=29 December 2013}}</ref> Its complex structure is due to multiple ejections of material from the ageing central star, which are distorted by the presence of a likely binary companion.<ref>{{cite web|url=http://www.nasa.gov/mission_pages/hubble/science/ngc5189.html|title=A Cosmic Holiday Ornament, Hubble-Style|last=Villard|first=Ray |date=18 December 2012|work=Hubble Space Telescope|publisher=NASA|access-date=31 December 2013}}</ref> Located 2.4° east of Eta Muscae is the magnitude-12.9 [[Engraved Hourglass Nebula]] (MyCn&nbsp;18),<ref>{{cite book |title=1001 Celestial Wonders to See Before You Die: The Best Sky Objects for Star Gazers |first=Michael E. |last=Bakich |publisher=Springer |location=New York, New York |date=2010 |isbn=978-1-4419-1777-5 |page=159 |url=https://books.google.com/books?id=qEhpS7d5ZdAC&pg=PA159}}</ref> which lies about 8000 light-years distant from Earth.<ref name="sahai99">{{cite journal|author=Sahai, Raghvendra |display-authors=4  |author2=Dayal, Aditya |author3=Watson, Alan M. |author4=Trauger, John T. |author5=Stapelfeldt, Karl R. |author6=Burrows, Christopher J. |author7=Gallagher, John S. III |author8=Scowen, Paul A. |author9=Hester, J. Jeff |author10=Evans, Robin W. |author11=Ballester, Gilda E. |author12=Clarke, John T. |author13=Crisp, David |author14=Griffiths, Richard E. |author15=Hoessel, John G. |author16=Holtzman, Jon A. |author17=Krist, John |author18=Mould, Jeremy R.|date=1999|title=The Etched Hourglass Nebula MYCN 18. I. ''Hubble Space Telescope'' Observations |bibcode-access=free |journal=The Astronomical Journal|volume=118|issue=1 |pages=468–76|doi=10.1086/300939|bibcode = 1999AJ....118..468S |doi-access=free }}</ref> To Eta's west lies [[IC 4191]], a compact bluish planetary nebula of magnitude 10.6,<ref name="Griffiths">{{cite book|last=Griffiths|first=Martin|date=2012|title=Planetary Nebulae and How to Observe Them |pages=198–200| isbn=978-1-4614-1782-8 |publisher=Springer |location=New York, New York |url=https://books.google.com/books?id=gsI1S_KVDxoC&q=musca+nebula&pg=PA198}}</ref> thought to lie around 10,750 light-years away from Earth.<ref name=zhang93>{{cite journal|last=Zhang|first=C.Y.|date=1993|title=On the Distance to Galactic Planetary Nebulae|journal=Astrophysical Journal, Part 1|volume=410|issue=1|pages=239–50|bibcode=1993ApJ...410..239Z|doi=10.1086/172740}}</ref> West of Epsilon Muscae is [[NGC 4071]], a large, diffuse planetary nebula of magnitude 12.7 with a magnitude 12 central star,<ref name="Griffiths"/> thought to lie around 4000 light-years away from Earth.<ref name=zhang93/> The [[Coalsack Nebula]] is a [[dark nebula]] located mainly in neighbouring Crux that intrudes into Musca.<ref>{{cite book|last=Darling|first=David J. |title=The Universal Book of Astronomy: from the Andromeda Galaxy to the Zone of Avoidance|publisher=Wiley|location=Hoboken, New Jersey|date=2004|page=351|isbn=0-471-26569-1}}</ref> [[NGC 4463]] is an [[open cluster]] located on its southwestern border.<ref name="inglis">{{cite book|last=Inglis|first=Mike|title=Astronomy of the Milky Way: Observer's Guide to the Southern Sky|publisher=Springer |location=New York, New York|date=2004|page=83|isbn=1-85233-742-7|url=https://books.google.com/books?id=1r0qvMjSCGAC&pg=SA3-PA12}}</ref> Around five light-years across, it is located around 3400 light-years away.<ref name=bagnall/>

The comparatively old [[globular cluster]] [[NGC 4833]] near Delta Muscae was catalogued by Lacaille in 1755.<ref name="streicher"/> It is 21,200&nbsp;light-years distant and somewhat obscured by dust clouds near the [[galactic plane]]. The globular cluster [[NGC 4372]] near Gamma Muscae is fainter and likewise partially obscured by dust, but spans more [[arc minute]]s.<ref name="turnleft">{{cite book|last=Consolmagno|first=Guy |title=Turn Left at Orion: Hundreds of Night Sky Objects to See in a Home Telescope – and How to Find Them|publisher=Cambridge University Press|location=Cambridge, United Kingdom|date=2011|page=235 |isbn=978-1-139-50373-0|url=https://books.google.com/books?id=h3712RgWkOYC&pg=PA235}}</ref><!-- cites previous two sentences --> It is 18,900&nbsp;light-years away from Earth and 23,000&nbsp;light-years distant from the centre of the Milky Way. Its extremely low [[metallicity]] indicates it is very old—one of the oldest clusters in the Milky Way.<ref name="o'meara">{{cite book |title=Deep-Sky Companions: Southern Gems |first=Stephen James |last=O'Meara |publisher=Cambridge University Press|location=Cambridge, United Kingdom |date=2013 |pages=218–21 |isbn=978-1-107-01501-2|url=https://books.google.com/books?id=S5QIEKns33sC&pg=PA220}}</ref><!-- cites previous two sentences --> Extending south from it is the [[Dark Doodad Nebula]], resembling a dark L-shaped river through a bright field of stars.<ref name="Coe2007">{{cite book |url=https://books.google.com/books?id=roXyxpcc9MsC&pg=PA95 |title=Nebulae and How to Observe Them |publisher=Springer |location=New York, New York |first=Steven R. |last=Coe |page=95 |date=2007 |isbn=978-1-84628-482-3}}</ref> Another [[dark nebula]] in the constellation is [[BHR 71]].