NGC 6791
| NGC 6791 | |
|---|---|
Detail from the Kepler image showing NGC 6791. Celestial north is to the left.a | |
| Observation data (J2000 epoch) | |
| Right ascension | 19h 20m 53s |
| Declination | +37° 46.3′ |
| Distance | ~13,300 ly (4078 pc) |
| Apparent magnitude (V) | +9.5 |
| Apparent dimensions (V) | 16' |
| Physical characteristics | |
| One of the oldest known open clusters | |
| Other designations | C 1919+377, Cl Berkeley 46, OCl 142.0, GC 4492 |
| Associations | |
| Constellation | Lyra |
NGC 6791 is an open star cluster in the Lyra constellation. It was discovered by Friedrich August Theodor Winnecke in 1853. At roughly 8 billion years old, and with an iron to hydrogen abundance ratio that is more than twice that of the Sun, it is one of the oldest and most metal-rich clusters in the Milky Way. This is contrary to the typical rule-of-thumb where older means more metal-poor. Compounded with the fact that it has an unusually high population of stars, NGC 6791 is among the most studied clusters in the sky.