M10
NGC 6254
Object Data
- Catalog Designation
- M10
- Type
- GlobularCluster
- Constellation
- Ophiuchus
- Magnitude
- 6.6
- Right Ascension
- 16h 57m 08.9s
- Declination
- -04° 05' 58.1"
- Distance
- 14,300 light-years
- Angular Size
- 15.1
Survey Image
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About M10
Description
M10 is a bright globular cluster in Ophiuchus, about 14,300 light-years from Earth. It is relatively loose for a globular cluster, with a concentration class VII. The cluster spans about 83 light-years and contains hundreds of thousands of stars estimated to be around 11.4 billion years old.
Observing Tips
Located about 8 degrees east-southeast of the bright star Rasalhague (Alpha Ophiuchi) and only 3.4 degrees from M12. The pair fits in the same binocular field. A 4-inch telescope shows a bright, round glow that begins to appear granular at 100x. An 8-inch telescope resolves stars well into the core. Compare with nearby M12 — M10 is more compact and concentrated. Best observed from June through August.
History
Discovered by Charles Messier on May 29, 1764. William Herschel resolved it into stars in 1784, estimating it contained 'a beautiful cluster of extremely compressed stars.' It forms a famous visual pair with nearby M12.
Fun Facts
M10 has an unusually high number of blue stragglers — stars that appear younger and bluer than they should be for such an old cluster. These are likely formed from stellar mergers or mass transfer between close binary stars. The cluster orbits the Milky Way, passing through the galactic plane roughly every 53 million years.
Community Photos (1)
Credit: Manfred Höcherl. License: CC BY-SA 4.0. (Wikimedia Commons)
Skybred Feb 28, 2026
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