An Etymological Dictionary of Astronomy and Astrophysics
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A line profile in which the emission is on the blue side of the absorption. It is usually interpreted as the redshift of the absorption component relative to emission lines, which necessitates infall of matter.

→ inverse; → P Cygni; → line; → profile.

A feature in a stellar spectrum showing strong hydrogen and helium emission lines with absorption lines on their blueward wing. This line profile indicates a strong outflow of matter from a star. → inverse P Cygni line profile.

After → P Cygni star.

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.