Origin of chondrules

Chondrites are a type of stony meteorite consisting of an agglomeration of millimeter-sized globules (chondrules) that are thought to be unchanged since the original condensation out of the gaseous nebula from which the sun and solar system formed. Planetesimals are bodies with dimensions of 10^(-3) to 10^(3) meters that are believed to form planets by a process of accretion. The term "accretion" refers to an aggregation, an increase in the mass of a body by the addition of smaller bodies that collide and adhere to it, provided the relative velocities are low enough for coalescence. In principle, one can distinguish "first generation" planetesimals from second (or third, etc.) generation planetesimals formed by the breakup of first generat- ion planetesimals, all of the events determined by granule densities, planetesimal densities, gravitational fields, orbits, orbital velocities, and so on. In addition, in complex gravitat- ional systems consisting of many small orbiting bodies influenced by the gravitational field of a large orbiting body, there are "resonances" that may arise, amplifications of gravitational perturbations due to various periodicity parameters, and these perturbations may play an important role in the gravitational evolution of the entire system. The term "bow shock" refers to the shock wave produced by the interaction of the supersonic solar wind (the continuous flow of hydrogen and helium gas from the sun) with the magnetic field of a planet (in this case, Jupiter). The chondrules are considered an important theoretical link to the origin and early development of our solar system, and various models have been formulated based on their chemistry and physical properties. ... ... Now Weidenschilling et al (3 authors at 3 installations, US IT) present a model for the production of chondrules by heating of debris from disrupted first-generation planetesimals, with Jovian resonances exciting planetesimal orbiting eccentricities enough to cause collisional disruption and melting of dust by bow shocks in the nebular gas. The authors suggest the age of chondrules may indicate the times of Jupiter's formation and dissipation of gas from the asteroidal region, and that their model reconciles the present apparently incompatible temporal and dynamical constraints on theory produced by observations and analysis.