View source for Stellar-wind bubble

A '''stellar-wind bubble''' is a cavity [[Light-year|light-years]] across filled with hot gas blown into the [[interstellar medium]] by the high-velocity (many thousand km/s) [[stellar wind]] from a single massive [[star]] of [[Stellar classification|type]] [[O-type star|O]] or [[B-type main-sequence star|B]]. Weaker stellar winds also blow bubble structures, which are also called '''astrospheres'''. The [[heliosphere]] blown by the [[solar wind]], within which all the major [[Planet|planets]] of the [[Solar System]] are embedded, is a small example of a stellar-wind bubble.

[[File:Hubble_Sees_a_Star_‘Inflating’_a_Giant_Bubble_(26534662246).jpg|right|thumb|The [[Bubble Nebula]] (NGC 7635), imaged by the [[Hubble Space Telescope]], is seven [[Light year|light years]] across]]

Stellar-wind bubbles have a two-shock structure.<ref>{{cite journal|last1=Castor|first1=J.|last2=McCray|first2=R.|last3=Weaver|first3=R.|date=1975|title=Interstellar Bubbles|journal=Astrophysical Journal Letters|volume=200|pages=L107–L110|bibcode=1975ApJ...200L.107C|doi=10.1086/181908}}</ref> The freely-expanding stellar wind hits an inner firing shock, where its [[kinetic energy]] is thermalized, producing 10<sup>6</sup>&nbsp;[[Kelvin|K]], [[X-ray]]-emitting [[Plasma (physics)|plasma]].  The hot, high-pressure, shocked wind expands, driving a shock into the surrounding interstellar gas. If the surrounding gas is dense enough (number densities <math>n > 0.1 \mbox{ cm}^{-3}</math> or so), the swept-up gas radiatively cools far faster than the hot interior, forming a thin, relatively [[Density|dense]] shell around the hot, shocked wind.

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[[Category:Astronomy]]