Stellar Wind
Fast continuous outflow of material (p+, e–, and atoms of heavier metals) ejected from stars. Stellar winds are characterized by speeds of 20–2,000 km/sec. The causes, ejection rates and speeds of stellar winds vary with the mass of the starSelf-luminous object held together by its own self-gravity. Often refers to those objects which generate energy from nuclear reactions occurring at their cores, but may also be applied to stellar remnants such as neutron stars.. In relatively cool, low-mass stars, such as the SunOur parent star. The structure of Sun's interior is the result of the hydrostatic equilibrium between gravity and the pressure of the gas. The interior consists of three shells: the core, radiative region, and convective region. Image source: http://eclipse99.nasa.gov/pages/SunActiv.html. The core is the hot, dense central region in which the, the wind is caused by the extremely high temperature (106s K) of the coronaExtended outer atmosphere of the Sun. The glow of the corona is a million times less bright than that of the photosphere; it can only be seen when the disk of the Sun is blocked during a total solar eclipse, or by using a coronagraph, which artificially blocks the disk Click on Term to Read More. This high temperature probably results from interactions between magnetic fields at the star’s surface, and gives the coronal gas sufficient energy to escape the gravitational attraction of the star. These stars eject only a tiny fraction of their mass per year as a stellar wind but this still represents losses of millions of tonnes of material each second. Over their entire lifetime, stars like our Sun lose only a tiny fraction of 1% of their mass through stellar winds.
In contrast, hot, massive stars can produce stellar winds ~109 times stronger than those of low-mass stars and over their short lifetimes, they can eject up to 50% of their initial mass as 2,000 km/sec winds. These stellar winds are driven directly by radiation pressureMinute pressure exerted by electromagnetic radiation (such as but not limited to light from the sun) on everything it encounters. This can be thought of as the transfer of momentum from photons as they strike the surface of the object. In the environs of stars such pressure can become important Click on Term to Read More from photons escaping the star. In some cases, high-mass stars can eject virtually all of their outer envelopes in winds. The result is a Wolf-Rayet starMassive stars at an advanced stage of stellar evolution, losing mass at a very high rate (right). They have masses typically >25 Msun and brief lifetimes. About 220 are known in our own Galaxy out of an estimated 1,000-2,000 such objects; most are hidden by dust. Wolf-rayet stars have average Click on Term to Read More. Stellar winds play an important part in the chemical evolution of the UniverseThat which contains and subsumes all the laws of nature, and everything subject to those laws; the sum of all that exists physically, including matter, energy, physical laws, space, and time. Also, a cosmological model of the universe., as they carry dust and metals back into the interstellar mediumMaterial between the stars, consisting of gas, dust and cosmic rays (high energy charged particles moving at nearly the speed of light). It comprises ~10% of visible matter in the disk of our Galaxy (Milky Way). Until recently it was generally assumed that silicates in the ISM were amorphous, but Click on Term to Read More where they will be incorporated into the next generation of stars.
