Open star clusters are widely distributed in our galaxy and represent a loose collection of stars which number from a
few dozen to a few hundred stars and are weakly-held gravitationally. Perhaps the three most famous such open clusters
are the Pleiades (M45) in Taurus, the Beehive (M44) in Cancer and the double cluster in Perseus. They are all
characterized with a handful of hot and white prominent stars and nebular material surrounding these stars.
Note: The list below represents an on-going project to image the
oldest known open clusters in our galaxy. The rankings and age estimates below are based on
"The age of the oldest Open Clusters" by Salaris et al (Astronomy & Astrophysics, 414: 163–174 (2004), see
here) and
"Diameters of Open Star Clusters" by van den Bergh (Astronomical Journal, 131: 1559-1564 (2006), see
here). Additional resources include
Astronomy Magazine (Mar/2004) as well as the online article here.
| Oldest Open Star Clusters (Reference: Salaris, 2004) |
|||||
|---|---|---|---|---|---|
 NGC 6791 in Lyr (10.20 billion yrs) |
 Berkeley 17 in Aur (10.06 billion yrs) |
 Berkeley 54 in Cyg (7.27 billion yrs) |
Arp-Madore 2 in Pup (7.24 billion yrs) |
 NGC 188 in Cep (6.30 billion yrs) |
|
Berkeley 32 in Mon (5.91 billion yrs) |
Berkeley 18 in Aur (5.69 billion yrs) |
Berkeley 56 in Cyg (5.67 billion yrs) |
Trumpler 5 in Mon (5.67 billion yrs) |
Melotte 66 in Pup (5.33 billion yrs) |
|
Berkeley 31 in Mon (5.32 billion yrs) |
King 2 in Cas (5.03 billion yrs) |
NGC 2243 in CMa (4.66 billion yrs) |
Berkeley 29 in Gem (4.34 billion yrs) |
 M67 in Cnc (4.30 billion yrs) |
|
Berkeley 22 in Ori (4.26 billion yrs) |
 NGC 1193 in Per (4.23 billion yrs) |
Berkeley 20 in Ori (4.05 billion yrs) |
|||
| Oldest Open Star Clusters (Reference: van den Bergh, 2006) |
|||||
|---|---|---|---|---|---|
Berkeley 17 in Aur (10.06 billion yrs) |
Berkeley 39 in Mon (7.94 billion yrs) |
NGC 1193 in Per (7.94 billion yrs) |
Saurer 1 in CMi (7.08 billion yrs) |
Berkeley 20 in Ori (6.03 billion yrs) |
|
King 2 in Cas (6.03 billion yrs) |
Berkeley 66 in Cas (5.01 billion yrs) |
Berkeley 12 in Per (4.68 billion yrs) |
Berkeley 70 in Aur (4.68 billion yrs) |
NGC 6791 in Lyr (4.37 billion yrs) |
|
Berkeley 18 in Aur (4.27 billion yrs) |
NGC 188 in Cep (4.27 billion yrs) |
Trumpler 5 in Mon (4.07 billion yrs) |
Berkeley 54 in Cyg (3.98 billion yrs) |
||