Jeudi 8 avril 1999
Molecular clouds are the birthplaces of stars. These gas clouds, which have masses up to several million times that of the Sun, are turbulent, magnetized, and self-gravitating.
Many of the properties of these clouds can be understood in terms of polytropic models in which the pressure varies as a power of the density ; such models have been used previously in astrophysics to model both stars and globular clusters.
Just as nuclear reactions power stars, so energy injection from newly formed stars provides the energy to maintain the turbulence in molecular clouds. Star formation appears to be governed by the rate at which the weakly ionized plasma in molecular clouds can slip through the magnetic field, and is confined to regions where the ionization is lowest..