Musca
What is Musca?
Constellations· Southern autumn · right below the Southern Cross. A small Fly clinging just beneath the Southern Cross. Set in the Milky Way, it is dense with stars, and the edge of the Coalsack dark nebula and the Hourglass Nebula both fall within it.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where Musca is in your sky right now: https://nowsky.org/solar/sky?sel=con:Musca — location and time set automatically, no login.
Stars of the figure
| Star | Magnitude |
|---|---|
| Alpha Muscae | 2.7 |
| Beta Muscae | 3.0 |
The 2 brightest of the 2 stars used in the figure (1 lines). Lower magnitude means brighter.
Constellation basics
| Season | Apr–May evenings; never visible from Korea |
|---|---|
| Brightest star | α Muscae, mag 2.7 |
| How to find | a small knot of stars just south of Crux |
| Area rank | 77th of 88 |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Frequently asked
- When can I see Musca?
- Apr–May evenings; never visible from Korea.
- How do I find Musca?
- a small knot of stars just south of Crux.
- What is the brightest star in Musca?
- Alpha Muscae, magnitude 2.7.
- Where is Musca in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
The nova that appeared in Musca in 1991 was a black hole
In January 1991 a nova was found in Musca brightening in X-rays and visible light at once. Nova Muscae 1991, as it was named, was unlike an ordinary nova in that its X-rays were overwhelmingly strong, and later spectroscopy showed a companion star circling an unseen object every 10.4 hours. Its mass came out at about seven Suns, beyond the limit for a neutron star, and it was judged a black hole.
The system, also called GRS 1124-683, is not a constant source like Cygnus X-1 but a transient that wakes once in decades, showing only the companion's light in quiet times. Its outbursts are the collapse of material accumulated in a disk, the same class as A0620-00 and V404 Cygni. The small constellation attached below the Southern Cross is a place that showed how a black hole first gets identified.
The constellation in depth
Musca is one of the twelve southern constellations drawn from the Dutch navigators' voyages of the 1590s; it began as a Bee and later settled into a Fly. Charts often showed the neighbouring Chamaeleon flicking its tongue at it. Because it clings directly beneath the Southern Cross, it is hard to miss from the southern hemisphere.
Alpha Muscae, the brightest star at magnitude 2.7, is a blue-white member of the Scorpius–Centaurus association that pulsates slightly. The southern part of the Coalsack dark nebula beside Crux spills into the constellation, and the Hubble-imaged Hourglass Nebula (MyCn 18) and the globular clusters NGC 4833 and 4372 also lie here. Both clusters are within reach of a small telescope on a dark night.
At declinations of −64° to −75° it cannot be seen from Korea. In the southern hemisphere, wait for April or May evenings when the Southern Cross rides high and look for the small knot of stars just below it. In the Sky view, set Sydney or Cape Town on an April evening and zoom in beneath Crux.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.