M69 (Globular Cluster)
A globular cluster in Sagittarius, 2.5° from Kaus Australis and the same from M70. It is one of the most metal-rich globulars on record.
Globular cluster in Sagittarius. Magnitude 7.6.
Can you see it from Guyana?
From Georgetown (6.8° N) it climbs to 51° above the southern horizon at its highest; from Lethem (3.4° N), to 54° above the southern horizon. It is highest at midnight on the night of 27 Jun, in the middle of its season. The page works out tonight's rise, highest point and set for both towns in Guyana time (UTC-4), and where the Moon is.
What you'll see
- Your eyes: Not visible to the eye. It lies 2.5° north-east of Kaus Australis.
- 10x50 binoculars: A round glow, brighter towards the middle.
- A small telescope (80 to 100 mm): A small, bright, concentrated glow; M70 is 2.5° to the east at the same power.
- A camera: Tiny on camera: it needs 2,000 mm or more of focal length on a tracking mount.
How big, how bright, how far
- Size on the sky: 5.7′, 18% of the Moon's width (the Moon is about 31′ wide).
- Brightness: magnitude 7.6. Fainter than the faintest stars in Georgetown (4.3) and Lethem (6.0): binoculars or a telescope.
- Distance: 29,000 light-years. The light reaching your eye left it about 29,000 years ago.
- True size: 48 light-years across its catalogued outline; light crosses it in 48 years.
Apparent size from OpenNGC (Mattia Verga), CC-BY-SA-4.0.
What it is made of
- Type
- Globular cluster
- Mass
- About 138,000 times the Sun's mass
- Notable
- Metal-rich for a globular: [Fe/H] -0.64, richer than 124 of the 152 measured.
Measured: Which generation its red giants belong to (862 measured near its centre).
- Second generation: 57.5%, born from gas the first stars enriched
- First generation: 42.5%, ± 1.7%
Gas: searches of globular clusters mostly find only upper limits (Pancino et al. 2024, arXiv:2404.05548). Hubble ultraviolet colours split its red giants into a first generation and later, chemically enriched ones: 42.5% ± 1.7% first generation among 862 red giants (NGC 6637; Milone et al. 2017, MNRAS 464, 3636, Table 2).
Also in it, not measured:
- Stellar remnants: white dwarfs and neutron stars
- Almost no gas or dust: not in this tally
How we know: Distance from Gaia, Hubble and earlier distances to its stars, combined: Baumgardt & Vasiliev 2021, MNRAS 505, 5957; Baumgardt globular cluster database, combined_table.txt, retrieved 2026-10-21 (NGC 6637: 8.9 +/- 0.1 kpc). True size: the apparent size times the distance (apparent size: OpenNGC (Mattia Verga, CC BY-SA 4.0), commit 4e2398a2). Mass: Baumgardt globular cluster database, combined_table.txt (NGC 6637: 138,000 ± 2,470 Suns), retrieved 2026-10-21; Baumgardt & Vasiliev 2021, MNRAS 505, 5957.
More deep-sky objects: M70 (Globular Cluster) · M54 (Globular Cluster) · M28 (Globular Cluster) · Ptolemy Cluster (M7) · Globular Cluster M22 · Butterfly Cluster (M6)