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

1) A variable star in the constellation → Cygnus, and one of the most luminous stars in the Milky Way Galaxy. It is a → Luminous Blue Variable (LBV) star of → spectral type B2 Ia located about 7000 light-years away. It was unknown until the 17th century, when it suddenly brightened to third magnitude. It briefly disappeared and returned, and today has a magnitude of about 4.8.
2) A member of a class of high-luminosity, early-type stars, in which spectral lines have a characteristic → P Cygni profile.

P, letter of alphabet; Cygni, pertaining to → Cygnus; → star.