View source for Stellar-wind bubble

{{Short description|Cavity of hot gas blown from a star}}
{{redirect|Astrosphere|the astrosphere of the Sun|Heliosphere}}
[[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]]s across]]

A '''stellar-wind bubble''' is a cavity [[light-year]]s across filled with hot gas blown into the [[interstellar medium]] by the high-velocity (several 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]]s of the [[Solar System]] are embedded, is a small example of a stellar-wind bubble.

Stellar-wind bubbles have a two-shock structure.<ref>{{cite journal| bibcode=1975ApJ...200L.107C |last= Castor|first=J. |last2=McCray|first2=R. |last3=Weaver|first3=R. | title=Interstellar Bubbles| date=1975| journal=Astrophysical Journal Letters| volume=200| pages=L107–L110| doi=10.1086/181908| doi-access=free}}</ref> The freely-expanding stellar wind hits an inner termination 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 qid=Q120634820>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 dense shell around the hot, shocked wind.

==See also==
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* [[Cosmic wind]]
* [[Stellar wind]]
* [[Solar wind]]
* [[Planetary wind]]
* [[Colliding-wind binary]]
* [[Pulsar wind nebula]]
* [[Galactic superwind]]
* [[Superwind]]
{{div col end}}

== References ==
{{reflist}}

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[[Category:Stellar astronomy]]
[[Category:Galactic astronomy]]
[[Category:Interstellar media]]


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