Clusters of Open Clusters
We examine the grouping of open clusters (OCs) in layer clusters and the ages of open clusters that form clusters of OCs. For this goal we use Lynga  catalog which consists of 370 OCs with known distances and ages. 180 of 370 OCs are used to form 51 clusters of OCs. Here the number of young cluster of OCs (which contain at least 1 OC with age no more than 10^7 yrs) is found 29. 19 of them are coincident with the OB associations. Old OCs which are having the age 10^8 yrs are oviding to attend the young clusters of OCs. This shows that star formation has a duration up to 10^8 yrs in a molecular complex. Old OCs do not form rich clusters. They come together rarely with larger age spans. 22 old clusters of old OCs are found and number of OCs in them does not exceed 4. No coincidence is observed between OB associations and old clusters of OCs. Keywords: Open clusters, OB associations, star formation regions.
AYDIN, Cemal; ALBAYRAK, Berahitdin; GOZEL, İsfendiyar; and GUSEINOV, Oktay H. (1997) "Clusters of Open Clusters," Turkish Journal of Physics: Vol. 21: No. 7, Article 11. Available at: https://journals.tubitak.gov.tr/physics/vol21/iss7/11