Globular cluster in Sagittarius
M69
Unusually rich in heavy elements for a globular, which means it formed later than most of its kind — after enough stars had lived and died to salt the gas it condensed from. It sits in a crowded field and takes some finding.
It is a small globular by the standards of this list, perhaps sixty light-years across, and lies about a thousand light-years closer to the galactic centre than we do — which is the likely reason it is enriched. Formed late, formed near the middle, and made from gas several generations of stars had already been through.
- Catalogue
- M69
- Type
- Globular cluster
- Constellation
- Sagittarius
- Distance
- 29,700 light-years
- Apparent magnitude
- 7.6
- Surface brightness
- 20.5 mag/□″
- Apparent size
- 7′
- Right ascension
- 18h 31m
- Declination
- −32.35°
- Found by
- Nicolas-Louis de Lacaille, 1752
Small enough that its 7.6 magnitudes arrive concentrated rather than smeared: 20.5 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 | Challenge | Challenge | Challenge | Challenge |
At the eyepiece
Small, faint and set in a field so crowded with Milky Way stars that the first job is establishing that you have found the cluster rather than a knot of foreground. It does not resolve at ordinary apertures. Best treated as one stop in a Sagittarius sweep rather than a target.
When, and from where
Highest in the middle of the night in June. A southern object: overhead at 32°S, and low and murky from Britain and the northern United States even at its best. North of 58°N it never rises.
| Latitude | Highest it gets | |
|---|---|---|
| 60°N Oslo, Anchorage | — | Never rises |
| 51°N London, Calgary | 7° | Low — in the murk |
| 40°N New York, Madrid | 18° | Low — in the murk |
| 30°N Cairo, Houston | 28° | |
| 0°N the equator | 58° | |
| 33°S Sydney, Cape Town | 89° |
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 M69 itself, not from the middle of Sagittarius.
- M70 Globular cluster 2.5° apart Sagittarius · magnitude 7.9 · binoculars from Bortle 5 or darker
- M54 Globular cluster 5.4° apart Sagittarius · magnitude 7.6 · binoculars from Bortle 5 or darker
- M28 Globular cluster 7.6° apart Sagittarius · magnitude 6.8 · binoculars from Bortle 6 or darker
- M7 Ptolemy's Cluster 8.2° apart Scorpius · magnitude 3.3 · binoculars from Bortle 9 or darker
One of 110. Positions J2000; the sky is the final authority.