Open cluster in Auriga
M37
The best of the three Auriga clusters by a clear margin — several hundred stars, dense enough to sparkle, with a distinctly orange one near the middle. If you only look at one of them, look at this.
It is perhaps five hundred million years past forming — old enough to have giants in it at all — and it holds something like five hundred stars against M36's sixty. Messier found it himself in 1764 along with the other two, having been told about none of them — three clusters in one constellation on consecutive sweeps.
- Catalogue
- M37
- Type
- Open cluster
- Constellation
- Auriga
- Distance
- 4,500 light-years
- Apparent magnitude
- 6.2
- Surface brightness
- 21.7 mag/□″
- Apparent size
- 24′
- Right ascension
- 5h 52m
- Declination
- +32.55°
- Found by
- Giovanni Batista Hodierna, before 1654
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
Several hundred stars at 150mm, dense enough to look granular at the edges of vision, with one distinctly orange point near the middle that makes the rest look bluer by contrast. If you have time for one Auriga cluster, this is the one. Moderate power, and take your time over it.
When, and from where
Highest in the middle of the night in December. Passes overhead at 33°N and rises from everywhere except the far south — below 57°S it never clears the horizon.
| Latitude | Highest it gets | |
|---|---|---|
| 60°N Oslo, Anchorage | 63° | Never sets |
| 51°N London, Calgary | 72° | |
| 40°N New York, Madrid | 83° | |
| 30°N Cairo, Houston | 87° | |
| 0°N the equator | 57° | |
| 33°S Sydney, Cape Town | 24° |
Nearby in the sky
The whole catalogue →One more of the catalogue sits within five degrees, close enough to take in on the same night without moving far. Everything below is measured from M37 itself, not from the middle of Auriga.
- M36 Open cluster 3.8° apart Auriga · magnitude 6.3 · binoculars from Bortle 9 or darker
- M38 Open cluster 5.9° apart Auriga · magnitude 7.4 · binoculars from Bortle 9 or darker
- M35 Open cluster 9.0° apart Gemini · magnitude 5.3 · binoculars from Bortle 9 or darker
- M1 Crab Nebula 11° apart Taurus · magnitude 8.4 · binoculars from Bortle 5 or darker
One of 110. Positions J2000; the sky is the final authority.