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  • Print publication year: 1999
  • Online publication date: June 2012

12 - Winds colliding with the interstellar medium

Summary

Stars interact with the surrounding interstellar medium (ISM), both through their ionizing radiation and through the mass, momentum, and energy that is transferred by way of their winds. The extreme ultraviolet radiation from hot stars leads to ionized nebulae or H II regions around young stars. In the case of low mass stars about to become white dwarfs, the radiation leads to the ionization of planetary nebulae.

The mass loss in stellar winds leads to a recycling of matter back to the interstellar medium, and because of the nuclear processing that occurs in the interiors of stars, the matter which is returned is often chemically enriched. In the cases of late type giants and carbon rich Wolf-Rayet stars, dust grains are produced in the winds, so the outflows may carry grain enriched material into the interstellar medium. These grains could play a role in the next generation of star formation. There are also dynamical effects associated with wind-interstellar medium interactions. The collisions of the winds with their surroundings produce ‘wind bubbles’, and the momentum transfer helps to maintain the random velocities of interstellar clouds that otherwise would be damped out by the dissipative effects of cloud collisions.

The winds of ‘massive stars’ tend to have the greatest effect on the ISM, because their mass loss rates are large, and the massive stars that are hot also have winds that are very fast and carry large momentum fluxes.