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

The process whereby a → galaxy evolves from a disturbed to an ordered system, as it develops into a → rotation dominated → settled disk.

→ disk; → settling.

A process occurring in → protoplanetary disks whereby relatively large → dust grains settle to the disk midplane. These grains, with sizes from → micron to → millimeter, grow from smaller dust grains and will eventually give rise to a planetary system.

→ dust; → settling.

A physical process occurring in → stellar atmospheres whereby in a very stable atmosphere → heavy elements are gravitationally pulled down preferentially. If such an atmosphere is stable for long periods of time, the → absorption lines of heavy elements may therefore become very weak. Observationally, the star seems to contain only → hydrogen and → helium. Gravitational settling takes place in the Sun at the bottom of the outer → convective zone where helium is dragged down, leading to a surface He abundant smaller than the cosmic value. It occurs also in the atmospheres of → brown dwarfs and → planets. See also → radiative levitation, → element diffusion, → thermal diffusion.

→ gravitational; → settling.

The act of a person or thing that settles. → disk settling, → dust settling.

→ settle; → -ing.