IAU Constellation (Mus) · Genitive: Muscae · Southern Sky

Musca (The Fly) Constellation Sky Guide

Musca IAU constellation (138 sq deg, rank 77): compact May southern Milky Way figure directly south of Crux, led by +2.69 Alpha Muscae and Dark Doodad.

Solid-Angle Area138 sq deg (Rank #77 of 88)
Best Evening MonthMay
Visibility Latitudes+15° to −90°
Brightest StarAlpha Muscae (+2.69)

Sky Navigation & Astrophysical Context

Positioned immediately south of Acrux at the foot of the Southern Cross and beneath the dark silhouette of the Coalsack Nebula, Musca spans 138 square degrees of the rich southern Milky Way (ranking 77th in area). First charted by Pieter Dirkszoon Keyser and Frederick de Houtman in 1595–1597 as 'De Vlieghe' and included in Bayer's 1603 Uranometria as Apis (the Bee) before Nicolas-Louis de Lacaille renamed it Musca Australis to avoid confusion with Apus, it is the only official constellation depicting an insect.

Because its five brightest stars—Alpha (+2.69), Beta (+3.05), Delta (+3.61), Lambda (+3.64), and Gamma Muscae (+3.87)—lie within a compact 6° × 4° skew-quadrilateral and tail belong largely to the Lower Centaurus–Crux OB subgroup, Musca stands out prominently to the unaided eye just below Crux. Beta Muscae is a famous tight binary of two nearly equal B2 V main-sequence stars (+3.5 and +4.0) orbiting every 194 years.

Musca contains a remarkable variety of southern deep-sky objects: directly west of Alpha and Gamma Muscae snakes the 3°-long 'Dark Doodad' Nebula (Sandqvist 149), one of the sharpest filamentary molecular dust lanes in the sky, terminated at its southern end by the bright globular cluster NGC 4372 (Caldwell 108); eastern Musca also hosts globular cluster NGC 4833 (Caldwell 105), the Spiral Planetary Nebula (NGC 5189), and the Engraved Hourglass Planetary Nebula (MyCn 18).

Bordering IAU Constellations: Crux, Centaurus, Carina, Chamaeleon, Apus, Circinus.

Equatorial Center Position & Transit Altitude

Musca is centered near Right Ascension 12h 33m 36s, Declination −70° 09′ 36″ (The Fly).

J2000 Equatorial Sky Position (Musca) +90° 0° −90° 24h 12h RA 0h Peak Meridian Altitude 0° 40°N Lat 50° 30°S Lat RA: 12h 33m 36s Dec: −70° 09′ 36″ Epoch: J2000.0 · 138 sq deg (Rank #77) First-party vector diagram derived from IAU / CDS SIMBAD / Gaia DR3 astrometry.

Practical Star-Hopping & Observing Tips

  • Look 4° directly south of Acrux (Alpha Crucis) across the southern edge of the Coalsack to spot +2.69 Alpha Muscae and +3.05 Beta Muscae.
  • Sweep 10×50 binoculars or a wide-field telescope just west of Gamma Muscae to trace the 3° black ribbon of the Dark Doodad Nebula ending at globular cluster NGC 4372.
  • In a 100 mm+ telescope, split Theta Muscae (a Wolf-Rayet triple system with a +7.5 companion 5.3 arcseconds away) and S-shaped planetary nebula NGC 5189.

Notable Celestial Objects in & Near Musca

Cataloged Stars and Deep-Sky Objects Associated with Musca
ObjectFamilyClassificationRA (J2000)Dec (J2000)Min. Instrument
Omega Centauri (NGC 5139 Cluster)globular-clustersGlobular cluster / stripped dwarf galaxy nucleus13h 26m 47.24s-47° 28′ 46.1″Naked eye (south of 35°N)
Carina Nebula (NGC 3372 Star-Forming Cloud)nebulaeGiant H II region and massive OB star-forming complex10h 45m 07.00s-59° 52′ 00.0″Naked eye and binoculars (south of 30°N)

Scientific Sources Cited