Berlin 2005 – scientific programme

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EP: Extraterrestrische Physik

EP 20: Poster-Session III: Astrophysik

EP 20.2: Poster

Tuesday, March 8, 2005, 09:00–19:00, Poster TU BH

The Bonn program for photometric and kinematic studies of open clusters — •Michael Geffert and Jörg Sanner — Sternwarte der Universität Bonn

Open clusters are gravitational bound systems of stars with common origin and common motion. They are objects suited to trace the structure of the Milky Way and stellar evolution. About 1600 open clusters were found so far in our Galaxy. However, only 38% of all open clusters have been confirmes by photometric observations (colour magnitude diagrams). In addition, kinematic data of stars in the region of the cluster are available only for 10% of these objects.

In the Bonn program photometric and kinematic (proper motion) observations of stars in the region of open clusters have been performed. They are used to separate real clusters from spurious concentrations of stars and - for confirmed star clusters - members from field stars. The determination of the true stellar content of the clusters may help to find a possible universal initial mass function (IMF) of star formation. Moreover, distances and mean motions of clusters lead to basic parameters of the structure of the Milky Way. In rare cases even the internal motions of stars in the cluster may be determined.