Messier 28
| Messier 28 | |
|---|---|
Globular cluster Messier 28 in Sagittarius | |
| Observation data (J2000 epoch) | |
| Class | IV |
| Constellation | Sagittarius |
| Right ascension | 18h 24m 32.89s |
| Declination | –24° 52′ 11.4″ |
| Distance | 18.26 ± 0.98 kly (5.6 ± 0.3 kpc) |
| Apparent magnitude (V) | 6.8 |
| Apparent dimensions (V) | 11′.2 |
| Physical characteristics | |
| Mass | 5.51×105 M☉ |
| Radius | 30 ly |
| VHB | 15.55 ± 0.10 |
| Metallicity | [Fe/H] = –1.32 dex |
| Estimated age | 12.0 Gyr |
| Notable features | Contains first pulsar discovered in a globular |
| Other designations | GCl 94, M 28, NGC 6626 |
Messier 28 or M28, also known as NGC 6626, is a globular cluster of stars in the center-west of Sagittarius. It was discovered by French astronomer Charles Messier in 1764. He briefly described it as a "nebula containing no star... round, seen with difficulty in 31⁄2-foot telescope; Diam 2′."