1. Lines of right ascension
R.A. is the celestial equivalent to longitude. Astronomers attached the grid to the sky, so objects’ right ascensions don’t change as Earth rotates. R.A. is measured in hours, minutes, and seconds.
2. Sharpless object (Sh)
American astronomer Stewart Sharpless cataloged 313 HII regions (star-forming areas composed of hydrogen that glow because of irradiation from nearby stars).
3. Barnard object (B)
American astronomer Edward Emerson Barnard (1857–1923) cataloged 349 dark nebulae in A Photographic Atlas of Selected Regions of the Milky Way.
4. Messier object (M)
French comet hunter Charles Messier (1730–1817) created a catalog that contains 109 of the finest deep-sky objects.
5. Bayer (Greek) letter
German mapmaker Johannes Bayer (1572–1625) labeled the brightest stars of each constellation using Greek letters. His system appeared in Uranometria in 1603.
6. Star name
Some 200 bright stars have common names. Most star names come to us from Arab and Greek astronomers and their star charts.
7. New General Catalogue (NGC) object
In 1888, Dreyer listed 7,840 deep-sky objects in a catalog that appeared in Memoirs of the Royal Astronomical Society.