An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A very extensive envelope of cold gaseous materials surrounding evolved cool stars, notably → red giants, → red supergiants (→ Mira variables), or → asymptotic giant branch stars. The typical size of such envelopes is several thousands times that of the stellar radius and their temperature ranges from 1000 to10 K. Circumstellar envelopes result from mass loss from the central star (10^-7 to 10^-4→ solar masses per year) and expand with moderate velocities (10 to 15 km sec^-1). The low temperature of the envelope is at the origin of the formation of molecules, which in certain conditions provide → maser emission (H₂O, OH, SiO). Similarly, dust grains form in the envelope produce an → infrared excess emission.

→ circumstellar; → envelope.

1) A → convective zone situated beneath the surface of solar type stars.
2) Stellar models show that → massive stars also possess an outer convective envelope encompassing several percent of the stellar radius. Fast rotation amplifies the size of the convective envelope in → OB stars and developes anisotropic convective envelops (Maeder et al. 2008, A&A 479, L37).

→ convective; → envelope

A shell of dust or gas expanding out from an astronomical object such as a star or a comet's nucleus.

From Fr. enveloppe, from O.Fr. envoloper "to envelop," from en- "in" + voloper "wrap up," of obscure origin, perhaps related to M.L. aluppa "a very thin piece or slice of wood" and influenced by L. volvere "to roll."

Pušé, noun from pušidan "to cover; to put on;" Mid.Pers. pôšidan, pôš- "to cover; to wear;" cf. Mid.Pers. pôst; Mod.Pers. pust "skin, hide;" O.Pers. pavastā- "thin clay envelope used to protect unbaked clay tablets;" Skt. pavásta- "cover," Proto-Indo-Iranian *pauastā- "cloth."

A → radiative zone occupying the outer parts of a star.

→ radiative; → envelope.