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Stellar wind

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Flow of gas ejected from the upper atmosphere of a star

This article is about gas ejected from the atmosphere of stars. For other uses, seeStellar wind (disambiguation).

This image shows the wind from the star LL Orionis generating abow shock (the bright arc) as it collides with material in the surroundingOrion Nebula.

Astellar wind is a flow of gas ejected from theupper atmosphere of astar. It is distinguished from thebipolar outflows characteristic of young stars by being lesscollimated, although stellar winds are not generally spherically symmetric.

Differenttypes of stars have different types of stellar winds.

Post-main-sequence stars nearing the ends of their lives often eject large quantities of mass in massive ( $\scriptstyle {\dot {M}}>10^{-3}$ solar masses per year), slow (v = 10 km/s) winds. These includered giants andsupergiants, andasymptotic giant branch stars. These winds are understood to be driven byradiation pressure ondust condensing in the upper atmosphere of the stars.^[1]^[2]^[3]^[4]^[5]^[6]

YoungT Tauri stars often have verypowerful stellar winds.^{[citation needed]}

Massive stars oftypes O andB have stellar winds with lower mass loss rates ( $\scriptstyle {\dot {M}}<10^{-6}$ solar masses per year) but very high velocities (v > 1–2000 km/s). Such winds are driven by radiation pressure on the resonance absorption lines of heavy elements such as carbon and nitrogen.^[7] These high-energy stellar winds blowstellar wind bubbles.

Inplanetary nebula NGC 6565, a cloud of gas was ejected from the star after strong stellar winds.^[8]

G-type stars like theSun have a wind driven by their hot, magnetizedcorona. The Sun's wind is called thesolar wind. These winds consist mostly of high-energyelectrons andprotons (about 1keV) that are able to escape the star'sgravity because of the hightemperature of thecorona.

Stellar winds from main-sequence stars do not strongly influence the evolution of lower-mass stars such as the Sun. However, for more massive stars such as O stars, the mass loss can result in a star shedding as much as 50% of its mass whilst on the main sequence: this clearly has a significant impact on the later stages of evolution. The influence can even be seen for intermediate mass stars, which will becomewhite dwarfs at the ends of their lives rather than exploding assupernovae only because they lost enough mass in their winds.^{[citation needed]}

References

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^Lamers, Henny J. G. L. M. (1999).Introduction to stellar winds. Cassinelli, Joseph P. Cambridge, England: Cambridge University Press.ISBN 0521593980.OCLC 38738913.
^"Dust Envelopes".Stellar Physics. Astrophysical Institute Potsdam. Archived fromthe original on 1 October 2016. Retrieved7 April 2014.
^Mattsson, L.; Wahlin, R.; Höfner, S. (January 2010). "Dust driven mass loss from carbon stars as a function of stellar parameters".Astronomy and Astrophysics.509: A14.arXiv:1107.1771.doi:10.1051/0004-6361/200912084.ISSN 0004-6361.S2CID 17360256.
^Höfner, S.; Gautschy–Loidl, R.; Aringer, B.; Jørgensen, U. G. (February 2003)."Dynamic model atmospheres of AGB stars".Astronomy & Astrophysics.399 (2):589–601.doi:10.1051/0004-6361:20021757.ISSN 0004-6361.
^Sandin, C.; Höfner, S. (June 2003)."Three-component modeling of C-rich AGB star winds".Astronomy & Astrophysics.404 (3):789–807.arXiv:astro-ph/0304278.doi:10.1051/0004-6361:20030515.ISSN 0004-6361.
^Sandin, C.; Höfner, S. (January 2004). "Three-component modeling of C-rich AGB star winds".Astronomy & Astrophysics.413 (3):789–798.arXiv:astro-ph/0309822.doi:10.1051/0004-6361:20031530.ISSN 0004-6361.S2CID 15641925.
^Castor, J.; Abbott, D. C.;Klein, R. I. (1975). "Radiation-driven winds in Of stars".Astrophys. J.195:157–174.Bibcode:1975ApJ...195..157C.doi:10.1086/153315.
^"The long goodbye". Retrieved27 July 2015.

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