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V.V. Makarov (MSC, JPL)
In the Solar neighborhood, devoid of giant molecular clouds and star-forming regions, stars younger than the Pleiades are found in considerable numbers, including several T Tauri stars. Some of the nearby young stars seem to be isolated field objects, others are members of loose swarms (mini-associations) of about 20 stars each, e.g., the TWA, Tucana and Horologium swarms. By tracking positions and motions of some 30 nearby young stars and 40 OB associations, clusters and kinematic groups backward in time, we find that most of the former were not dislodged from open clusters, associations or active SFR. The two best studied swarms, the \beta Pic and TWA are rapidly expanding. However, even in the most compact form, their size was quite large (~ 20 pc), and the initial relative velocities too fast to interpret them as disintegrating non-hierarchical multiple systems. Both swarms had a fairly close passage of the Lower Centaurus Crux OB association 10-12 Myr ago, but were not parts of the Sco-Cen complex. The origin of several young stars appear to be associated with the giant complex of clouds and SFR in the Ophiuchus.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.