NGC 1851 (Globular Cluster)
A bright, compact globular cluster in Columba, about 39,000 light-years away. Hubble finds three groups of stars in it, not the usual two: a third, iron-enriched group sits beside the first and second generations.
Globular cluster in Columba. Magnitude 7.1.
Can you see it from Guyana?
From Georgetown (6.8° N) it climbs to 43° above the southern horizon at its highest; from Lethem (3.4° N), to 47° above the southern horizon. It is highest at midnight on the night of 7 Dec, 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 7.8° south-west of Phact.
- 10x50 binoculars: A round glow, brighter towards the middle.
- A small telescope (80 to 100 mm): A bright, concentrated glow; at high power its edge turns grainy.
- A camera: Tiny on camera: it needs 2,000 mm or more of focal length on a tracking mount. The photo above is a near-infrared Gemini view of its core.
How big, how bright, how far
- Size on the sky: 9′, 29% 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: 39,000 light-years. The light reaching your eye left it about 39,000 years ago.
- True size: 100 light-years across its catalogued outline; light crosses it in 100 years.
Apparent size from OpenNGC (Mattia Verga), CC-BY-SA-4.0.
What it is made of
- Type
- Globular cluster
- Mass
- About 283,000 times the Sun's mass
- Notable
- Milone et al. class it Type II: besides its first and second generations it holds a third group of stars enriched in iron.
Measured: Which generation its red giants belong to (1,022 measured near its centre).
- Second generation: 73.6%, born from gas the first stars enriched
- First generation: 26.4%, ± 1.5%
Milone et al. class it Type II: it also holds a third, iron-enriched group of stars, so this two-way split is the simplest reading. 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: 26.4% ± 1.5% first generation among 1,022 red giants (NGC 1851; 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 1851: 11.95 +/- 0.13 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 1851: 283,000 ± 3,630 Suns), retrieved 2026-10-21; Baumgardt & Vasiliev 2021, MNRAS 505, 5957.
.jpg){kind=link}
More deep-sky objects: M79 (Globular Cluster) · M41 (Open Cluster) · NGC 2451 (Open Clusters) · NGC 2362 (Open Cluster) · NGC 2477 (Open Cluster) · NGC 2547 (Open Cluster)