Evolved stars

Large surveys of emission from the carbon monoxide (CO) molecule and other molecules show that evolved stars are losing mass in the form of stellar winds at relatively low outflow speeds. The current observations suggest that, roughly speaking, the winds are isotropic (equal in all directions) and that the mass loss rates and outflow velocities are constant with time. Observations of very large numbers of stars will be required, perhaps of thousands, in order to achieve a model that will allow to draw conclusions of the evolution in question, through physical and chemical parameters.

Winds from cool evolved stars are probably the dominant source of refractory dust grains in the interstellar medium. They are the star-stuff from which we and our planet were formed. The grains manifest themselves through thermal emission extending from the far infrared through millimeter -wavelengths.  ALMA is able to analyze the chemical composition of these stars and of the ejected material.