AI overview
Messier 22 is a globular cluster—a spherical collection of hundreds of thousands of old stars tightly bound together by gravity—located about 10,500 light-years away in the constellation Sagittarius. It's one of the brightest globular clusters visible from Earth and has been studied extensively by astronomers to understand stellar evolution and the early history of our galaxy.
AI-generated from the Wikipedia summary — may contain errors.
Key facts
- Class
- VII
- Constellation
- Sagittarius
- Right ascension
- 18 36 23.94
- Declination
- –23 ° 54 ′ 17.1 ″
- Distance
- 10.6 ± 1.0 kly (3 ± 0.3 kpc )
- Apparent dimensions v
- 32 arcmins
- Mass
- 2.9 × 10 M ☉
- Radius
- 50 ± 5 ly
- Metallicity
- [ Fe/H ] = –1.49 dex
- Estimated age
- 12 Gyr
- Notable features
- One of four globulars known to contain a planetary nebula.
- Other designations
- NGC 6656, GCl 99
via Wikipedia infobox
Article
Messier 22 or M22, also known as NGC 6656 or the Great Sagittarius Cluster, is an elliptical globular cluster of stars in the constellation Sagittarius, near the Galactic bulge region. It is one of the brightest globulars visible in the night sky. The brightest stars are 11th magnitude, with hundreds of stars bright enough to resolve with an 8" telescope. It is just south of the sun's position in mid-December, and northeast of Lambda Sagittarii (Kaus Borealis), the northernmost star of the "Teapot" asterism.
M22 was one of the first globulars to be discovered, in 1665 by Abraham Ihle and it was included in Charles Messier's catalog of comet-like objects in 1764. It was one of the first globular clusters to be carefully studied – first by Harlow Shapley in 1930. He placed within it roughly 70,000 stars and found it had a dense core. Then Halton Arp and William G. Melbourne continued studies in 1959. Due to the large color spread of its red giant branch (RGB) sequence, akin to that in Omega Centauri, it became the object of intense scrutiny starting in 1977 with James E. Hesser et al.