An Etymological Dictionary of Astronomy and Astrophysics
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A small patch of → nebulosity in a → star-forming region, created when fast-moving → jets of material (with speeds up to about 1000 km per sec) from a newborn star collide with the → interstellar medium.

→ Herbig AeBe star; Guillermo Haro (1913-1988), who first in 1940s studied these objects in detail and recognized that they were a by-product of the star formation process; → object.