Definitions

Open cluster family

In astronomy, an open cluster family is a group of approximately coeval (age range $sim$30 Myr) young open star clusters located in a relatively small region of the Galactic disk (radius $sim$250 pc).

Introduction

Open star clusters do not form in isolation but tend to be found in complexes (Efremov 1978), within star forming regions. A significant number of known young open clusters are found in groups when age, spatial distribution, and kinematics are taken into account simultaneously.

Piskunov et al. (2006) found evidence for four open cluster complexes (OCCs) of different ages containing up to a few tens of clusters. There is significant statistical evidence for the presence of at least five dynamical families of young open clusters in the Milky Way disk. In order of increasing distance: Orion, Scutum-Sagittarius, Cygnus, Scorpius, and Cassiopeia-Perseus. These families are associated to the Galactic spiral structure, they are short-lived and the progenitors of classical superclusters, moving groups, and stellar streams (de la Fuente Marcos & de la Fuente Marcos 2008).