A stellar-wind bubble is a cavity
light-years across filled with hot gas blown into the
interstellar medium
In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstellar ...
by the high-velocity (several thousand km/s)
stellar wind from a single massive
star
A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth ma ...
of
type O or
B. Weaker stellar winds also blow bubble structures, which are also called astrospheres. The
heliosphere blown by the
solar wind
The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the sol ...
, within which all the major
planets of the
Solar System are embedded, is a small example of a stellar-wind bubble.
Stellar-wind bubbles have a two-shock structure.
The freely-expanding stellar wind hits an inner termination shock, where its kinetic energy is thermalized, producing 10
6 K,
X-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30 ...
-emitting
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
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
*
Wolf–Rayet nebula
References
Stellar astronomy
Galactic astronomy
Interstellar media
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