accretion

interstellar medium

Barnard object

interstellar reddening

bipolar outflow

nebula (plural nebulae)

Bok globule

nebulosity

circumstellar accretion disk

OB association

cluster (of stars)

open cluster

cocoon nebula

protoplanetary disk (proplyd)

dark nebula

protostar

dust grains

recombination

emission nebula

reflection nebula

evolutionary track

stationary absorption lines

*fluorescence

stellar association

giant molecular cloud

stellar evolution

H II region

supernova remnant

Herbig-Haro object

supersonic

interstellar extinction

T Tauri star