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

A combining form meaning "lover of, attracted to" that specified by the initial element.

-phile, also -phil, from M.L. -philus, from Gk. -philos, common suffix in personal names (such as Theophilos), from philos "loving, dear," from philein "to love," which is of unknown origin.

-dust, from dust "friend; lover;" Mid.Pers. dôst "friend;" O.Pers. dauštar- "friend;" Av. zaoša- "pleasure," zuš- "to like," zušta- "loved;" cf. Skt. jos- "to like, be pleased, enjoy," jósa- "satisfaction," jóstar- "loving;" Gk. geuomai "to taste;" L. gustare "to taste."

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.

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.

P, referring to pressure; → mode.

Same as → parity symmetry.

→ parity; → symmetry.

→ compressional wave.

P, referring to → pressure; → wave.

A prefix meaning thick.

From Fr. pachy-, from L., from Gk. pachys "thick," akin to Av. bazah "high, deep," Baloci baz "thick, dense," ON bingar "heap," Latvian biezs "dense, thick."

Bazâ-, from Av. bazah, Baloci baz, as above; cf. Waxi bâj "thickness," variant dabz, → concentrated.

The difference between the isotopic mass of a nuclide and its mass number divided by its mass number. The packing fraction is a measure of the stability of the nucleus.

Packing, from the verb pack "to put together in a pack," from the noun pack, from M.E. pak, packe, from M.D. pac or perhaps M.L.G. pak; → fraction.

Barxé, → fraction; anbâštegi quality noun of anbâštan, anbârdan "to fill, to replete;" Mid.Pers. hambāridan "to fill;" from Proto-Iranian *ham-par-, from prefix ham- + par- "to fill;" cf. Av. par- "to fill," parav-, pauru-, pouru- "full, much, many;" O.Pers. paru- "much, many;" Mid.Pers. purr "full;" Mod.Pers. por "full, much, very;" PIE base *pelu- "full," from *pel- "to be full;" cf. Skt. puru- "much, abundant;" Gk. polus "many," plethos "great number, multitude;" O.E. full.

1) Something consisting of or regarded as having two parts or pieces joined together. → pair annihilation; → pair production.
2) Two identical, similar, or corresponding things.

M.E., from O.Fr. paire, from L. paria "equals," neuter plural of par (genitive paris) "a pair, counterpart, equal."

1) Joft "pair, couple," Lori, Laki jeft, Qâyeni jof, Tabari jeft, Mid.Pers. yuxt "pair, couple," Av. yuxta- "a team of horses," from yaog- "to yoke, harness, put to; to join, unite," infinitive yuxta, Mid.Pers. jug, ayoxtan "to join, yoke," Mod.Pers. yuq "yoke;" cf. Skt. yuga- "yoke," Gk. zygon "yoke," zeugnyanai "to join, unite," L. jugare "to join," from jugum "yoke," P.Gmc. *yukam, E. yoke; PIE *yeug- "to join."
Hamâl, from ham- "together, with; same, equally, even" (Mid.Pers. ham-, like L. com- and Gk. syn- with neither of which it is cognate. O.Pers./Av. ham-, Skt. sam-; also O.Pers./Av. hama- "one and the same;" Skt. sama-; Gk. homos-; originally identical with PIE numeral *sam- "one," from *som-. The Av. ham- appears in various forms: han- (before gutturals, palatals, dentals) and also hem-, hen-) + suffix -âl, → -al.

Mutual destruction of a particle and its antiparticle, such as an electron-positron pair, when they collide. The total energy of the two particles is converted into energy as gamma rays. It is the inverse process to → pair production.

→ pair; → annihilation

An instability arising from the → pair production inside a → massive star leading to energetic → supernova explosions. The pair instability occurs when, late in the star's life, the core reaches a sufficiently high temperature after → carbon burning, a condition in which the pair production can take place. The pairs of electron and positron annihilate to form a neutrino and an anti-neutrino. Consequently, the pressure drops and the outer layers fall in onto the core. The temperature and pressure increase rapidly and eventually titanic nuclear burning causes an extraordinary explosion with energies higher than 10⁵¹ erg. See also → pair-instability supernova and → pulsational pair-instability supernova.

→ pair; → instability.

The creation of an → elementary particle and its → antiparticle from a → boson. For example, the formation of an → electron and a → positron in the interaction of high-energy → gamma ray photons, having at least 1.02 Mev, with an → atomic nucleus (γ → e^- + e⁺). The → rest masses of the electron and positron being 0.51 MeV each, the excess energy will be carried away by these two particles. Pair production is the inverse process to → pair annihilation.

→ pair; → production

→ pair instability

→ pair; → instability.

A special type of → supernova that would result from the → pair instability in → supermassive stars with a mass range between 140 and 260 Msun in a low → metallicity environment. Such objects descended from the → Population III stars in the early history of the Universe. Such supernovae are the most powerful thermonuclear explosions in the Universe. Pair-instability supernovae may have played an important role in the synthesis of → heavy elements. Moreover, the energetic feedback of the processed elements to their surroundings could have affected the structure and evolution of the early Universe (See, e.g., Fryer et al. 2001, ApJ 550, 372; Heger & Woosley 2002, ApJ 567, 532). See also → pulsational pair-instability supernova.

→ pair; → instability; → supernova.

In nuclear physics, the extra binding energy associated with pairs of nucleons of the same kind. This quantity expresses the fact that nuclei with odd numbers of neutrons and protons have less energy and are less stable than those with even numbers of neutrons and protons.

Pairing, verbal noun of → pair; → energy.

The roof of the → mouth, separating the oral and nasal cavities. → hard palate; → soft palate.

M.E., from O.Fr. palat and directly from L. palatum "roof of the mouth."

Kâm "roof of the mouth," of unknown origin.

Lacking in color, not bright, weak in color or shade.

M.E., from O.Fr. paile "pale, light-colored," from L. pallidus "pale, pallid, colorless," from pallere "be pale, grow pale."

Pâl, from p(ox) + âl, a combination of (Delijân) pox "pale" + (Kurd) âl "pale."

A prefix meaning "old, ancient" especially in reference to former geologic time periods, e.g. → paleoclimatology, → paleolithic, and → paleomagnetism.

From Gk. palaio-, combining form of palaios "old, ancient," from palai "long ago, far back," from PIE root *kwel- "to turn, move about," also "far"

Pârin, pâriné "ancient," also "last year" (contraction of pâr sâl), related to pir "old;" Mid.Pers. pir "old, aged, ancient;" Av. parô (adv.) "before, before (of time), in front (of space);" cf. Skt. puáh, combining form of puras "before (of time and place), in front, in advance."
Dirin, diriné "old, ancient, of times past," from dir "old, antique; a long while" + suffix -in. The first component from Mid.Pers. dêr, variants dagr, drâz "long" (Mod.Pers. derâz "long," variant Laki, Kurdi derež); O.Pers. darga- "long;" Av. darəga-, darəγa- "long," drājištəm "longest;" cf. Skt. dirghá- "long (in space and time);" L. longus "long;" Gk. dolikhos "elongated;" O.H.G., Ger. lang; Goth. laggs "long;" PIE base *dlonghos- "long." The second component -in adj. suffix, from Mid.Pers. -ên (as in âhênên, zarrên), from Av. -aēna- (ayanhaēna- "made of iron," zaranaēna- "golden"); cf. Skt. -ēna-.

The climate during a past geologic time or before historical records.

→ paleo-; → climate.

The study of past → climates throughout → geologic and → historic time (paleoclimates), and the causes of their variations.

→ paleo-; → climatology.