An Etymological Dictionary of Astronomy and Astrophysics

5 terms — P › P

P PA PE PF PG PH PI PL PO PR PS PT PU PY

P Cygni profile   فراپال ِ P Cygni   farâpâl-e P Cygni Fr.: profil P Cygni 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. See also: After → P Cygni star.

P Cygni star   ستاره‌ی ِ P Cygni   setâre-ye P Cygni Fr.: étoile P Cygni 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. A member of a class of high-luminosity, early-type stars, in which spectral lines have a characteristic → P Cygni profile. See also: P, letter of alphabet; Cygni, pertaining to → Cygnus; → star.

p mode   ترز ِ p، مُد ِ ~   tarz-e p, mod-e ~ Fr.: mode p Acoustic waves trapped inside stars, which act as a resonating cavity, exhibiting millions of oscillation modes or standing waves. Same as → pressure mode. P-mode oscillations in the Sun have frequencies in the 0.2-5.5 mHz range. They are particularly intense in the 2-4 mHz range, where they are often referred to as solar “5-minute oscillations.” See also → pulsation mode. See also: P, referring to pressure; → mode.

P-symmetry   همامونی ِ همالی   hamâmuni-ye hamâli Fr.: symétrie de parité Same as → parity symmetry. See also: → parity; → symmetry.

P-wave   موج ِ P   mowj-e P Fr.: onde P → compressional wave. See also: P, referring to → pressure; → wave.