Hubble Space Telescope image of a bubble-like cavity, called N44F, 35 light-years in diameter, which is being inflated by a stellar wind from a very hot star once buried inside a cold dense cloud. The central star in N44F is ejecting mass at a rate greater than a 100 million times that in the solar wind. The particles in this stellar wind move at 7 million kilometers per hour, compared with about 1.5 million kilometers per hour in the case of the Sun. N44F is located about 160,000 light-years away in the Large Magellanic Cloud. Credit: NASA, ESA, Y. Nazé (University of Liège, Belgium) and Y.-H. Chu (University of Illinois, Urbana).
A stellar wind is the continuous flow of gas from the surface of a star into space. It is
most intense toward the beginning and the end of a star's life, as exemplified
by T Tauri stars, on the one hand, and red
giants and supergiants, on the
Among the most extreme stellar winds, resulting in a loss of 10–6 solar mass or more per year, are those that occur in X-ray binaries, in which in O and B stars are being stripped by a compact companion (either a neutron star or a black hole).
During their time on the main sequence, most stars blow a very modest stellar wind; in the Sun's case this amounts to a mass loss of only about 10–14 solar mass per year (see solar wind). Stellar winds represents an important mechanism by material is returned to the interstellar medium to be recycled as a new generation of stars.