Open cluster in Puppis
M93
A compact wedge of about eighty stars, with a pair of orange giants near the middle giving it some colour. The last object Messier discovered himself; everything after this came from Méchain. Messier logged it in March 1781 and then handed the search over, and everything from M104 onward came from Méchain's sweeps.
About eighty members, some eighty million years old, and the wedge shape is real rather than an accident of the brighter stars — a genuinely compact cluster in a part of Puppis with little else in it.
- Catalogue
- M93
- Type
- Open cluster
- Constellation
- Puppis
- Distance
- 3,600 light-years
- Apparent magnitude
- 6.2
- Surface brightness
- 21.5 mag/□″
- Apparent size
- 22′
- Right ascension
- 7h 45m
- Declination
- −23.87°
- Found by
- Charles Messier, 1781
Magnitude 6.2 for the cluster as a whole, though that is a sum rather than a thing you see: what reaches you is a scatter of separate stars, and whether you catch it depends on how bright the brightest of them are. Why surface brightness is the number that matters.
Could you see it?
Straightforward with the naked eye from Bortle 3 or darker; with 10×50 binoculars from Bortle 9.
| Sky | Eye | 10×50 | 80mm | 130mm | 200mm |
|---|---|---|---|---|---|
| Bortle 1 21.9 mag/□″ | Easy | Easy | Easy | Easy | Easy |
| Bortle 2 21.7 mag/□″ | Easy | Easy | Easy | Easy | Easy |
| Bortle 3 21.4 mag/□″ | Easy | Easy | Easy | Easy | Easy |
| Bortle 4 20.9 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 5 20.3 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 6 19.3 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 7 18.6 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 8 18.1 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 9 17.8 mag/□″ | No | Easy | Easy | Easy | Easy |
At the eyepiece
A compact wedge, brighter and more concentrated than most open clusters of its size, and it holds together well under moderate power. Two of its members glow distinctly warm against the rest. Among the better winter clusters, and far less visited than it deserves.
When, and from where
Highest in the middle of the night in January. Overhead at 24°S and southerly enough to sit low from northern Europe, though never out of reach there — only north of 66°N does it stop rising at all.
| Latitude | Highest it gets | |
|---|---|---|
| 60°N Oslo, Anchorage | 6° | Low — in the murk |
| 51°N London, Calgary | 15° | Low — in the murk |
| 40°N New York, Madrid | 26° | |
| 30°N Cairo, Houston | 36° | |
| 0°N the equator | 66° | |
| 33°S Sydney, Cape Town | 81° |
Nearby in the sky
The whole catalogue →Nothing else in the catalogue is especially close; the nearest is 9.1° apart, which is a separate trip rather than a nudge of the tube. Everything below is measured from M93 itself, not from the middle of Puppis.
- M46 Open cluster 9.1° apart Puppis · magnitude 6.1 · binoculars from Bortle 9 or darker
- M47 Open cluster 9.6° apart Puppis · magnitude 4.4 · binoculars from Bortle 9 or darker
- M41 Open cluster 14° apart Canis Major · magnitude 4.5 · binoculars from Bortle 9 or darker
- M50 Open cluster 18° apart Monoceros · magnitude 5.9 · binoculars from Bortle 9 or darker
One of 110. Positions J2000; the sky is the final authority.