M12 (Globular Cluster)
A globular cluster in Ophiuchus, 3.3° from M10 and at almost the same distance. It covers more sky than M10, 11 arcminutes against 9, but holds about half the mass.
Globular cluster in Ophiuchus. Magnitude 7.1.
Can you see it from Guyana?
From Georgetown (6.8° N) it climbs to 81° above the southern horizon at its highest; from Lethem (3.4° N), to 85° above the southern horizon. It is highest at midnight on the night of 1 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 8.4° east of Yed Prior.
- 10x50 binoculars: A round glow, brighter towards the middle. M10 is 3.3° to the south-east.
- A small telescope (80 to 100 mm): A large glow with a weaker centre than M10; at 100x its outer stars begin to show.
- 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: 11.1′, 36% of the Moon's width (the Moon is about 31′ wide).
- Brightness: magnitude 7.1. Fainter than the faintest stars in Georgetown (4.3) and Lethem (6.0): binoculars or a telescope.
- Distance: 16,700 light-years. The light reaching your eye left it about 16,700 years ago.
- True size: 54 light-years across its catalogued outline; light crosses it in 54 years.
Apparent size from OpenNGC (Mattia Verga), CC-BY-SA-4.0.
What it is made of
- Type
- Globular cluster
- Mass
- About 106,000 times the Sun's mass
Measured: Which generation its red giants belong to (315 measured near its centre).
- Second generation: 60%, born from gas the first stars enriched
- First generation: 40%, ± 2.9%
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: 40.0% ± 2.9% first generation among 315 red giants (NGC 6218; 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 6218: 5.11 +/- 0.05 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 6218: 106,000 ± 1,890 Suns), retrieved 2026-10-21; Baumgardt & Vasiliev 2021, MNRAS 505, 5957.
More deep-sky objects: M10 (Globular Cluster) · M107 (Globular Cluster) · M14 (Globular Cluster) · IC 4665 (Open Cluster) · M9 (Globular Cluster) · M80 (Globular Cluster)