A circumstellar envelope (CSE) is a part of a
star
A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
that has a roughly spherical shape and is not gravitationally bound to the star core. Usually circumstellar envelopes are formed from the dense
stellar wind
A stellar wind is a flow of gas ejected from the upper atmosphere of a star. It is distinguished from the bipolar outflows characteristic of young stars by being less collimated, although stellar winds are not generally spherically symmetric.
D ...
, or they are present before the formation of the star. Circumstellar envelopes of old stars (
Mira variable
Mira variables (named for the prototype star Mira) are a class of pulsating stars characterized by very red colours, pulsation periods longer than 100 days, and amplitudes greater than one magnitude in infrared and 2.5 magnitude at visual wavelen ...
s and
OH/IR star
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An OH/IR star is an asymptotic giant branch (AGB) or a red supergiant or hypergiant (RSG or RHG) star that shows strong OH maser emission and is unusually bright at near-infrared wavelengths.
In the very late stages of AGB evolution, ...
s) eventually evolve into
protoplanetary nebulae, and circumstellar envelopes of
young stellar object
Young stellar object (YSO) denotes a star in its early stage of evolution. This class consists of two groups of objects: protostars and pre-main-sequence stars.
Classification by spectral energy distribution
A star forms by accumulation of mate ...
s evolve into
circumstellar disc
A circumstellar disc (or circumstellar disk) is a torus, pancake or ring-shaped accretion disk of matter composed of gas, dust, planetesimals, asteroids, or collision fragments in orbit around a star. Around the youngest stars, they are the re ...
s.
Types of circumstellar envelopes
*
Circumstellar envelopes of AGB stars
* Circumstellar envelopes around
young stellar object
Young stellar object (YSO) denotes a star in its early stage of evolution. This class consists of two groups of objects: protostars and pre-main-sequence stars.
Classification by spectral energy distribution
A star forms by accumulation of mate ...
s
See also
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Circumstellar dust Circumstellar dust is cosmic dust around a star. It can be in the form of a spherical shell or a disc, e.g. an accretion disk. Circumstellar dust can be responsible for significant extinction and is usually the source of an infrared excess for sta ...
*
Common envelope
In astronomy, a common envelope (CE) is gas that contains a binary star system. The gas does not rotate at the same rate as the embedded binary system. A system with such a configuration is said to be in a common envelope phase or undergoing comm ...
s
*
Stellar evolution
Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is cons ...
References
External links
The Structure and Evolution of Envelopes and Disks in Young Stellar Systems
{{Molecules detected in outer space
Stellar evolution