Globular cluster in Ophiuchus
M107
Méchain found it in 1782 and it then sat outside the catalogue for a century and a half, until Helen Sawyer Hogg added it in 1947 — the same astronomer whose plates of M14 turned out to have a nova sitting on them. A loose globular, and unusually for its kind it appears to have dust inside it.
The dust is the unusual part. Globulars are meant to have expelled or used up everything they had ten billion years ago, and dark patches inside one are hard to account for — the current suspicion is that the material is not the cluster's own. It is a loose, low-concentration cluster about eighty light-years across.
- Catalogue
- M107
- Type
- Globular cluster
- Constellation
- Ophiuchus
- Distance
- 20,900 light-years
- Apparent magnitude
- 8.1
- Surface brightness
- 21.7 mag/□″
- Apparent size
- 10′
- Right ascension
- 16h 33m
- Declination
- −13.05°
- Found by
- Pierre Méchain, 1782
Small enough that its 8.1 magnitudes arrive concentrated rather than smeared: 21.7 per square arcsecond, which is why it stands out from the sky better than its brightness alone suggests. Why surface brightness is the number that matters.
Could you see it?
Straightforward with 10×50 binoculars from Bortle 5.
| Sky | Eye | 10×50 | 80mm | 130mm | 200mm |
|---|---|---|---|---|---|
| Bortle 1 21.9 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 2 21.7 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 3 21.4 mag/□″ | No | 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 | Challenge | Challenge | Challenge | Challenge |
| Bortle 7 18.6 mag/□″ | No | No | No | No | No |
| Bortle 8 18.1 mag/□″ | No | No | No | No | No |
| Bortle 9 17.8 mag/□″ | No | No | No | No | No |
At the eyepiece
A loose, faint globular that begins to break into stars at around 200mm, with an irregular look that sets it apart from its neighbours in Ophiuchus. The last object added to the catalogue, and a quiet way to finish a list that opens with a supernova.
When, and from where
Highest in the middle of the night in May. Overhead at 13°S and southerly enough to sit low from northern Europe, though never out of reach there — only north of 77°N does it stop rising at all.
| Latitude | Highest it gets | |
|---|---|---|
| 60°N Oslo, Anchorage | 17° | Low — in the murk |
| 51°N London, Calgary | 26° | |
| 40°N New York, Madrid | 37° | |
| 30°N Cairo, Houston | 47° | |
| 0°N the equator | 77° | |
| 33°S Sydney, Cape Town | 70° |
Nearby in the sky
The whole catalogue →Nothing else in the catalogue is especially close; the nearest is 11° apart, which is a separate trip rather than a nudge of the tube. Everything below is measured from M107 itself, not from the middle of Ophiuchus.
- M80 Globular cluster 11° apart Scorpius · magnitude 7.3 · binoculars from Bortle 6 or darker
- M10 Globular cluster 11° apart Ophiuchus · magnitude 6.6 · binoculars from Bortle 5 or darker
- M12 Globular cluster 12° apart Ophiuchus · magnitude 6.7 · binoculars from Bortle 5 or darker
- M9 Globular cluster 12° apart Ophiuchus · magnitude 7.7 · binoculars from Bortle 5 or darker
One of 110. Positions J2000; the sky is the final authority.