Muska the fly header

Muska star map


This small constellation of 138 square degrees, just south of Crux is worth an evening of observing.  There are several double stars, two globular clusters and three challenging planetary nebulae.  Part of the Coalsack Nebula also spills over into Musca.

The constellation was originally named Apis the bee by Bayer in his star atlas in 1603, later changed to Musca Apis by Edmond Halley, then Musca Australis (the Southern Fly) by Lacaille to distinguish it from the Northern Fly on the back of Aries the Ram. Now it is just known as Musca.  A lot of change for such a small constellation.

It is easy to locate due to the distinguishing stars alpha (α) mag. 2.69, beta (β ) mag 3.0, gamma (γ) mag. 3.8, and delta (δ) mag 3.6.

Double Stars:  Beta Muscae is a white binary pair of magnitude 3.9 and 4.2, 520 ly away. The separation is 1.6 arc seconds, therefore a challenge for a telescope under 128mm (5 inch). High magnification in a good dark sky will be required to split it.

h 4498 a pair of deep yellow and white magnitude 7 and 7.8 stars and  h 4432 a white pair also observed by John Herschel in the 1800’s  of mag 5.5 and 7.5 are another two doubles for those keen Double Star observers to track down.

Globular Clusters:  NGC 4833 is a fairly large 7.4 magnitude globular cluster approximately 1 degree northeast of Delta Muscae and 13.5 arc minutes in size. It is 18,000 ly away.  4833 is easily located with binoculars.  Stars are resolved with a 100mm (4 inch telescope).  The resolution is quite clear with my 128 mm refractor, a fairly condensed cluster with scatterNGC6397 Globular clustered outliers.







Compare this with 6th magnitude NGC 6397 (right) in ARA and M4 (below) also 6th magnitude in Scorpius, one of our closest globulars at 7000 ly – both of these constellations are now returning to our night sky.


M4 globular clusterNGC6397 open cluster above

M4 Globular Cluster left





NGC 4372 a 7.8 magnitude globular near Gamma Mus is difficult to observe. The faint stars are spread over a large area of 18.60 arc minutes and there is a lane of dark absorbing matter in the region obscuring the view.

The delightful Dark Doodad Nebula drifts through southern skies, a tantalizing target for binoculars. The dusty cosmic cloud is seen against rich starfields just south of the prominent Coalsack Nebula and the Southern Cross. Stretching for about 3 degrees across this scene the Dark Doodad seems punctuated at its southern tip (lower left) by globular star cluster NGC 4372. The Dark Doodad’s well defined silhouette belongs to the Musca molecular cloud, but its better known alliterative moniker was first coined by astro-imager and writer Dennis di Cicco in 1986 while observing comet Halley from the Australian outback. The Dark Doodad is around 700 light-years distant and over 30 light-years long.

NGC 4372 and the dark doodad

Planetary Nebulae:

NGC 5189 pictured below also known as the Spiral Planetary, described in Hartung’s as “a bluish knot of light east, from which a bright curved bar passes axially west” giving the appearance of a barred spiral galaxy.  At magnitude 10 and 2.60 arc minutes in size it is fairly large, bright and should be visible with a 3 inch (75mm) telescope, including the spiral structure. When a star like our Sun is dying, it will cast off its outer layers, usually into a simple overall shape. Sometimes this shape is a sphere, sometimes a double lobe, and sometimes a ring or a helix. In the case of planetary nebula NGC 5189, however, no such simple structure has emerged.

ngc5189 planetary nebular

IC 4191,  another challenge, this small bright bluish planetary is only 5 arc seconds and magnitude 12. It can be located using the bright 6.4 magnitude orange star HD 113919, 9 arc minutes to the west. It sits at the north-west apex of a narrow triangle with two fainter stars.

It will be only a tiny point with a small 3 to 4 inch scope, the bluish disk should be visible with a 5 inch.

NGC 4071 is a very faint, very small 12.9 mag., 1.30 arc minute planetary found near the line between Epsilon and Mu Muscae. If you have a large aperture telescope you will need it to view and locate this obscure beauty?


Sources: Burnhams Celestial Handbook, Vol II, 1978; Hartung’s, 2nd Ed, Malin & Frew; Collins Stars & Planets 3rd Ed; Skywatching, David Levy 1995. Star Atlas Pro Version 6.1.

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