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

A collapsing object whose radius is less than its Schwarzschild radius must collapse into a singularity.

→ Penrose process; → theorem.

A diagram involving → formal compactification of → space-time used in → general relativity to describe the causal properties of the space-time. Only two of the space dimensions are shown and horizontal lines represent space, while vertical lines belong to time. The → null geodesicss are at 45°, which facilitates the visualization of → light cones. The major feature of Penrose-Carter diagram is representing the whole space-time on a finite surface, while putting → spacelike and → timelike infinities at finite distance.

Named for Roger Penrose (1931-) and Brandon Carter (1942-) who introduced it independently; → diagram.

Prefix denoting five, fivefold (e.g. pentacyclic, pentahedron, pentahydrate).

From Gk. pent-, penta-, combining forms from pente "five;" cognate with Pers. panj, E. five, as below.

Panj, from Mid.Pers. panj, Av. panca; cf. Skt. pánca; Gk. pente; L. quinque; O.E. fif, from P.Gmc. *fimfe (O.S. fif, O.H.G. funf); from PIE base *penk^we "five."

1) The portion of a shadow in which light from an extended source is partially but not completely cut off by an intervening body; the area of partial shadow surrounding the umbra.
2) The lighter part of a shadow during an eclipse. An observer standing in the penumbra of a Solar eclipse will see a partial eclipse.
3) The lighter zone surrounding the dark area (→ umbra) of a → sunspot. It consists of fine, light filaments which are approximately radial for sunspots with circular outline, but irregular for complex spots.

N.L., from L. pæne "almost" + → umbra "shadow."

Nimsâyé, from nim "mid-, half" (Mid.Pers. nêm, nêmag "half;" Av. naēma- "half;" cf. Skt. néma- "half") + sâyé, → shadow; →umbra.

Of or relating to a → penumbra.

→ penumbra; → -al.

A lunar eclipse that occurs when the Moon passes through the Earth's → penumbra, but misses the darker umbral shadow. Because the Moon is only partially dimmed, a penumbral eclipse is not impressive. Total penumbral eclipses are rare, and when these occur, that portion of the Moon which is closest to the umbra can appear somewhat darker than the rest of the Moon.

→ penumbral; → eclipse.

Any plant of the genus Paeonia, having showy, pink, red, or white, globular flowers. Originally cultivated in the temperate regions of Asia, China, Europe, and the northwest parts of North America.

M.E., from M. Fr. peonie, pioiné, from L.L. peonia, from L. pæonia, from Gk. paionia, perhaps from Paion, physician of the gods. The plant was recognized to possess many remedial properties, and was thus given an association with the gods.

Payoniyâ, loan from Gk, as above.

A peony-shaped nebula around the → Wolf-Rayet star WR 102ka as shown by the → Spitzer Space Telescope image at 24 μm. The formation of this infrared bright nebula is attributed to the recent evolutionary history of WR 102ka during → LBV-type eruptions and/or its strong → stellar wind (see, e.g., A. Barniske et al. 2008, A&A 486, 971).

→ peony; → star.

1) Persons indefinitely or collectively; persons in general.
2) Human beings, as distinguished from animals or other beings (Dictionary.com).

M.E. peple, from O.Fr. peupel "people, population, crowd; mankind," from L. populus "a people, nation; a multitude, crowd," of unknown origin.

Mardom "man, human being, mankind, people;" from Mid.Pers. mardôm "human being, man, mankind, people" (from *mard-tohm "seed of man"), from mard "man, humanity" (cognate with mordan "to die"); O.Pers. martiya-; Av. marəta- "mortal, man," maša- "mortal;" cf. Skt. márta- "mortal, man;" Gk. emorten "died;" L. mortalis "subject to death."

1) A prefix meaning "through, thoroughly, utterly, very."
2) Chemistry: A prefix used in the names of inorganic chemical compounds containing an element in its highest oxidation state or containing a large or the largest possible proportion of an element.

From L. per "through, during, by means of, on account of," cognate with Pers. par-, pirâ-, as below; cf. Gk. → peri- "around, about, beyond;" O.C.S. pre-; Russ. pere- "through;" Lith. per "through;" Goth. fair-; Ger. ver-; O.E. fer-.

Par-, per-, variants of pirâ- "around, about," from Mid.Pers. pêrâ; O.Pers. pariy "around, about;" Av. pairi "around, over," per- "to pass over, beyond;" cf. Skt. pari; Indo-Iranian *pari- "around;" cf. Gk. peri "around, about, beyond;" L. per "through," as above; PIE base *per- "through, across, beyond."

1) To become aware of, know, or identify by means of the senses.
2) To recognize, discern, envision, or understand (Dictionary.com).

M.E. perceiven, from Anglo-Fr. *perceivre, from O.Fr. percoivre "perceive, notice, see; understand," from L. percipere "obtain, seize entirely, take possession of," from L. → per- "thoroughly" + capere "to take," → concept.

Âgertidan, from â- intensive prefix + gertidan "to take, seize," → concept.

The mental product of the act of perceiving, as distinguished from the thing perceived.

→ perception.

The process of recognizing or identifying something. Usually employed of sense perception, when the thing which we recognize or identify is the object affecting a sense organ.

Verbal noun of → perceive.

Any salt of perchloric acid.

→ per-; → chlorate.

A colorless liquid, HClO₄, that reacts explosively with organic matter or other reducible materials.

→ perchlorate; → -ic; → acid.

1a) Corresponding to an ideal standard or abstract concept.
1b) Exactly fitting the need in a certain situation or for a certain purpose.
2) To bring to perfection or completion. See also: → perfect cosmological principle, → perfect cube, → perfect gas, → perfect lens, → perfect number, → perfect power, → perfect set, → perfect square.

From M.E. parfit, from O.Fr. parfit, from L. perfectus "completed," p.p. of perficere "accomplish, finish, complete," from per- "through, thoroughly, utterly, very" + facere "to make, do, perform;" cognate with Pers. dâdan "to give" (O.Pers./Av. dā- "to give, grant, yield," dadāiti "he gives;" Skt. dadáti "he gives;" Gk. tithenai "to place, put, set," didomi "I give;" L. dare "to give, offer;" Rus. delat' "to do;" O.H.G. tuon, Ger. tun, O.E. don "to do;" PIE base *dhe- "to put, to do").

Farsâxt, farsâz, literally "thorougly made," from far- intensive prefix "much, abundant; elegantly" (Mid.Pers. fra- "forward, before; much; around;" O.Pers. fra- "forward, forth;" Av. frā, fərā-, fra- "forward, forth; excessive;" cf. Skt. prá- "before; forward, in fron;" Gk. pro "before, in front of;" L. pro "on behalf of, in place of, before, for;" PIE *pro-) + sâxt, sâz "made," short for sâxté, sâzidé "made; make, construction, structure; style," present stem of sâxtan, sâzidan "to build, make, fashion; to adapt, adjust, be fit" (from Mid.Pers. sâxtan, sâz-, Manichean Parthian s'c'dn "to prepare, to form;" Av. sak- "to understand, to mark," sâcaya- (causative) "to teach").

The → assumption, adopted by the → steady-state theory, that all observers, everywhere at all times, would view the same large-scale distribution of matter in the → Universe in all regions and in every direction. In contrast to the → cosmological principle, the perfect cosmological principle adds the assumption that the Universe does not change with time on the large scale.

→ perfect; → cosmological; → principle.

An → integer of the form n³, where n is a → positive number. In other words, a → perfect power when k = 3.

→ perfect; → cube.

A hypothetical gas with molecules of negligible size that exert no intermolecular forces. Also called → ideal gas.

→ perfect; → gas.

A theoretical, ideal lens capable of producing perfect images. Used as a lens design and analysis tool to image collimated output from an afocal system.

→ perfect; → lens.