An Etymological Dictionary of Astronomy and Astrophysics

A list of 313 individual → H II regions in the → northern → Milky Way (north of declination -27°). It includes several → planetary nebulae, → supernova remnants, and → reflection nebulae. The first edition (Sh-1) was published in 1953 with 142 objects and second and final version (Sh-2) was published in 1959. The catalog categorizes the H II regions in terms of several parameters, such as diameter, form (circular, elliptical, irregular), structure (amorphous/filamentary), brightness, and number of associated stars, which are further discussed in terms of their spectral classes.

See also: Stewart Sharpless (1959) A Catalogue of H II Regions, ApJ Suppl. 4, 257; → catalog.