M71 (Globular Cluster)
A loose, small globular cluster in Sagitta, light for its kind at about 38,000 Suns. Its stars are rich in heavy elements for a globular, and more than half of its red giants are first-generation stars.
Globular cluster in Sagitta. Magnitude 7.2.
Can you see it from Guyana?
From Georgetown (6.8° N) it climbs to 78° above the northern horizon at its highest; from Lethem (3.4° N), to 75° above the northern horizon. It is highest at midnight on the night of 18 Jul, 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° north of Tarazed.
- 10x50 binoculars: A round glow, brighter towards the middle.
- A small telescope (80 to 100 mm): A loose, grainy glow that a small telescope starts to resolve; it looks more like a rich open cluster than a globular.
- 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: 6.9′, 22% of the Moon's width (the Moon is about 31′ wide).
- Brightness: magnitude 7.2. Fainter than the faintest stars in Georgetown (4.3) and Lethem (6.0): binoculars or a telescope.
- Distance: 13,000 light-years. The light reaching your eye left it about 13,000 years ago.
- True size: 26 light-years across its catalogued outline; light crosses it in 26 years.
Apparent size from OpenNGC (Mattia Verga), CC-BY-SA-4.0.
What it is made of
- Type
- Globular cluster
- Mass
- About 38,000 times the Sun's mass
- Notable
- Metal-rich for a globular: [Fe/H] -0.78, richer than 112 of the 152 globulars measured; and its first-generation share, 62%, is higher than in 50 of the 54 clusters Milone et al. measured.
Measured: Which generation its red giants belong to (132 measured near its centre).
- First generation: 62.2%, ± 3.8%
- Second generation: 37.8%, born from gas the first stars enriched
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: 62.2% ± 3.8% first generation among 132 red giants (NGC 6838; 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 6838: 4.0 +/- 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 6838: 37,800 ± 1,380 Suns), retrieved 2026-10-21; Baumgardt & Vasiliev 2021, MNRAS 505, 5957.
More deep-sky objects: M56 (Globular Cluster) · M29 (Open Cluster) · IC 4756 (Open Cluster) · Globular Cluster M15 · NGC 6633 (Open Cluster) · Wild Duck Cluster (M11)