Globular cluster in Scorpius
M80
In May 1860 a star inside this cluster flared up and briefly outshone the whole of it — T Scorpii, the first nova ever seen in a star cluster of any kind. It is still the only classical nova anyone is certain has gone off inside a globular.
T Scorpii reached about magnitude 7 and faded within weeks, and no photograph exists — everything known about it comes from eyes at eyepieces in 1860. The cluster is one of the denser ones in the catalogue and holds an unusual number of blue stragglers, which is what that density does to the stars caught in it.
- Catalogue
- M80
- Type
- Globular cluster
- Constellation
- Scorpius
- Distance
- 32,600 light-years
- Apparent magnitude
- 7.3
- Surface brightness
- 20.7 mag/□″
- Apparent size
- 9′
- Right ascension
- 16h 17m
- Declination
- −22.98°
- Found by
- Charles Messier, 1781
Small enough that its 7.3 magnitudes arrive concentrated rather than smeared: 20.7 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 the naked eye from Bortle 1 or darker; with 10×50 binoculars from Bortle 6.
| Sky | Eye | 10×50 | 80mm | 130mm | 200mm |
|---|---|---|---|---|---|
| Bortle 1 21.9 mag/□″ | Easy | 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 | Easy | Easy | Easy | Easy |
| Bortle 7 18.6 mag/□″ | No | Challenge | Challenge | Challenge | Challenge |
| Bortle 8 18.1 mag/□″ | No | Challenge | Challenge | Challenge | Challenge |
| Bortle 9 17.8 mag/□″ | No | No | No | No | No |
At the eyepiece
Very compact and very bright in the middle — a hard little knot that will not resolve at ordinary apertures. Sits between Antares and Beta Scorpii, so it is easy to find, and it makes an instructive contrast with M4 nearby, which is everything this one is not.
When, and from where
Highest in the middle of the night in May. Overhead at 23°S and southerly enough to sit low from northern Europe, though never out of reach there — only north of 67°N does it stop rising at all.
| Latitude | Highest it gets | |
|---|---|---|
| 60°N Oslo, Anchorage | 7° | Low — in the murk |
| 51°N London, Calgary | 16° | Low — in the murk |
| 40°N New York, Madrid | 27° | |
| 30°N Cairo, Houston | 37° | |
| 0°N the equator | 67° | |
| 33°S Sydney, Cape Town | 80° |
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 M80 itself, not from the middle of Scorpius.
- M4 Globular cluster 3.9° apart Scorpius · magnitude 5.6 · binoculars from Bortle 5 or darker
- M107 Globular cluster 11° apart Ophiuchus · magnitude 8.1 · binoculars from Bortle 5 or darker
- M19 Globular cluster 11° apart Ophiuchus · magnitude 6.8 · binoculars from Bortle 5 or darker
- M62 Globular cluster 12° apart Ophiuchus · magnitude 6.5 · binoculars from Bortle 6 or darker
One of 110. Positions J2000; the sky is the final authority.