Circumstellar envelope is the part of the star,
having roughly spherical shape and not gravitationally bound to the star core.
Usually circumstellar envelopes are formed from the dense stellar wind

Stellar wind

A stellar wind is a flow of neutral or charged 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.Different types of stars have...

 or present
before formation of the star. Circumstellar envelopes of the old stars are eventually evolving
into Protoplanetary nebulae, and circumstellar envelopes of the young stellar object

Young stellar object

Young stellar object denotes a star in its early stage of evolution.This class consists of two groups of objects: protostars and pre–main sequence stars. Sometimes they are divided by mass - massive YSO , intermediate mass YSO and brown dwarfs....

s are evolving into Circumstellar discs.

Types of circumstellar envelopes

• Circumstellar envelopes of AGB stars
• Circumstellar envelopes around young stellar object
  Young stellar object
  Young stellar object denotes a star in its early stage of evolution.This class consists of two groups of objects: protostars and pre–main sequence stars. Sometimes they are divided by mass - massive YSO , intermediate mass YSO and brown dwarfs....
  
  s

See also

• Circumstellar dust
  Circumstellar dust
  Circumstellar Dust is astronomical dust around a star. It can be in the form of a spherical shell or a disk, e.g. an accretion disk. Circumstellar dust can be responsible for significant extinction and is usually the source of an infrared excess for stars that have it.The motion of circumstellar...
  
  
• Common envelope
  Common envelope
  In astronomy, a common envelope refers to a short-lived phase in the evolution of a binary star in which the largest of the two stars has initiated unstable mass transfer to its companion star. Mass transfer is unstable when the radius of the donor star expands more rapidly or shrinks less...
  
  s
• Stellar evolution
  Stellar evolution
  Stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. Depending on the mass of the star, this lifetime ranges from only a few million years to trillions of years .Stellar evolution is not studied by observing the life of a single...
  
  
• CSE