The paper: “Multiple kinematical populations in Vela OB2 from Gaia DR1 data” of F. Damiani recently published on A&A

Many, maybe most, of the stars in our Galaxy born in clusters. However, even if star formation in clusters is one of the main modes of star formation in the Milky Way, we still have not fully understood how stellar clusters form, evolve, and disperse.

 

A detailed study on the evolution of stellar clusters requires the analysis of the spatial distribution of associated stars, together with an accurate determination of their motion (radial velocity and proper motion) and age. It looks easy… but it is actually a hard job…

 

Future observations of Gaia and recent data from the Gaia-ESO Survey will deeply improve our knowledge on the evolution of stellar clusters. A bright example is the study of the Gamma Velorum cluster, where two stellar populations with different dynamical properties have been identified (link).

 

In the paper: “Multiple kinematical populations in Vela OB2 from Gaia DR1 data”, recently published on Astronomy & Astrophysics (link), the astronomer Francesco Damiani of the Astronomical Observatory of Palermo and his collaborators further analyze the dynamical properties of the stellar population of Gamma Velorum, by the study of their proper motion. In the paper convincing evidence is presented supporting the existence of two different stellar populations, belonging to Gamma Velorum cluster and the nearby cluster NGC 2547, respectively. It is also speculated the presence of a group of stars formed during the tidal stripping of Gamma Velorum while passing nearby NGC 2547.  This important result has been possible mainly thanks to the Gaia-ESO Survey.

 

The figure (link) shows the proper motion space of the stars in Gamma Velorum cluster, with the two populations encompassed with the two boxes.