Messier 4
| Messier 4 | |
|---|---|
Globular star cluster Messier 4 | |
| Observation data (J2000 epoch) | |
| Class | IX |
| Constellation | Scorpius |
| Right ascension | 16h 23m 35.22s |
| Declination | −26° 31′ 32.7″ |
| Distance | 6.033 kly (1.850 kpc) |
| Apparent magnitude (V) | 5.6 |
| Apparent dimensions (V) | 26′.0 |
| Physical characteristics | |
| Mass | 8.4×104 M☉ |
| Radius | 35 light-years |
| Metallicity | = −1.07 dex |
| Estimated age | (12.2 ± 0.2) Gyr |
| Notable features | Closest globular cluster |
| Other designations | NGC 6121 |
![{\displaystyle {\begin{smallmatrix}\left[{\ce {Fe}}/{\ce {H}}\right]\end{smallmatrix}}}](./4c0821bd80891e071c08e7c7ee8e022baedf522c.svg)
Messier 4 or M4 (also known as NGC 6121 or the Spider Globular Cluster) is a globular cluster in the constellation of Scorpius. It was discovered by Philippe Loys de Chéseaux in 1745 and catalogued by Charles Messier in 1764. It was the first globular cluster in which individual stars were resolved.