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

1) Velocity with respect to the Local Standard of Rest.
2) Any velocity a galaxy has with respect to us that is not a Hubble law velocity due to the expansion of space.

→ peculiar; → velocity.

The quality or condition of being peculiar.

Noun form of → peculiar.

The Winged Horse. A large constellation in the northern hemisphere at 22h 50m right ascension, 20° north declination. The stars → Markab, → Scheat, and → Algenib form three corners of the famous Great → Square of Pegasus, which is completed by the star → Alpheratz from neighboring → Andromeda. Abbreviation: Peg; Genitive: Pegasi.

In Gk. mythology, Pegasus is the winged horse that was fathered by Poseidon with Medusa. When the head of Medusa was cut off by Perseus, the horse sprang forth from her pregnant body. Pegasus aided Perseus in his fight against both the Chimera and the Amazons.

Pegâsus, from Gk., as above; asb-e bâldâr "Winged Horse," referring to the Gk. mythology, from asb→ horse; bâl, → wing; dâr "having, possessor" (from dâštan "to have, to possess," Mid.Pers. dâštan, O.Pers./Av. root dar- "to hold, keep back, maintain, keep in mind," Skt. dhr-, dharma- "law," Gk. thronos "elevated seat, throne," L. firmus "firm, stable," Lith. daryti "to make," PIE *dher- "to hold, support").

To make worse; to cause to deteriorate. To endow (a word) with a less favorable meaning.

Back formation from → pejorative.

Pastârdan, literally "to render low, vile, bring down" from past "low, vile, abject," → platykurtic, + ârdan, short for âvardan, "to cause or produce; to bring," → cause.

1) Depreciation; a lessening in worth, quality, etc.
2) Semantic change in a word to a lower, less approved, or less respectable meaning.

Verbal noun of → pejorate.

1) Having negative connotations; tending to disparage or belittle.
2) A pejorative word, expression, etc.

From Fr. péjoratif, from L.L. peiorat-, p.p. stem of peiorare "make worse," from L. peior "worse," related to pessimus "worst," pessum "downward, to the ground," from PIE *ped-yos-, comparative of root *ped- "to walk, stumble, impair," → foot.

Pastârandé agent noun from pastârdan, → pejorate.

An → H II region, also known as IC 5067 and IC 5070, about 2,000 → light-years away in the constellation → Cygnus. It is part of a much larger, complex star-forming region also containing the larger and bright → North America Nebula.

So named because of its resemblance to a pelican on long exposure images. M.E. pellican; O.E. pellicane, from L.L. pelecanus, from Gk. pelekan "pelican:" → nebula.

When an electric current is sent through the junction between two different conductors or semiconductors, a quantity of heat is liberated or absorbed, depending on the direction of the current. The heat is proportional to the total electric charge crossing the junction. This effect is due to the existence of an electromotive force at the junction.

Named after Jean-Charles Peltier (1785-1845), French physicist and watchmaker, who discovered the effect in 1834; → effect.

1a) A slender tube of wood, metal, plastic, etc., containing a core or strip of graphite, a solid coloring material, or the like, used for writing or drawing.
1b) Anything shaped or used like a pencil.
2) A narrow set of lines, light rays, or the like, diverging from or converging to a point (Dictionary.com). → pencil of light.

M.E. pencel, from M.Fr. pincel, from L. penicillus "painter's brush or pencil," diminutive of peniculus "little tail," diminutive of penis "tail;" → light.

Medâd "pencil," of unknown origin.
Kelk "quill, pen," originally "hollow reed."
Bâriké, from bârik, → narrow, + nuance suffix -é; nur, → light.

A beam of radiant energy in the form of a narrow cone or cylinder.

→ pencil; → beam.

A small part of the → Vela supernova remnant with a narrow appearance. The Pencil Nebula measures about 0.75 → light-years across, is about 5 light-years long, and lies about 800 light-years from Earth. It is moving through the → interstellar medium at about 650 000 kilometres per hour.

→ pencil; → nebula.

A small bundle of → rays of light. See also → beam of light.

M.E. pencel, from M.Fr. pincel, from L. penicillus "painter's brush or pencil," diminutive of peniculus "little tail," diminutive of penis "tail;" → light.

Bâriké, from bârik, → narrow, + nuance suffix -é; nur, → light.

In its simple form, a device consisting of a body suspended from a fixed point on the end of a string to move to and fro by the action of gravity and acquired momentum. The period of oscillation for small amplitudes of swing is determined by the formula T = 2π √(l/g).

From Mod.L. pendulum, noun use of neuter of L. pendulus "hanging down," from pendere "to hang."

Âvang, related to âvixtan, âviz- "to hang" (akin to bixtan, biz- "to shake, to sort out, to sift"); Mid.Pers. âwixtan "to hang" (Sogdian wyc "to move, shake;" Chorasmian wc- "to tremble, shake;" Ossetic wigyn "to shake," awynzyn "to hang"), from prefixed (â-) Proto-Iranian base *uij-, *uic- "to shake, swing;" cf. Av. vij- "to shake, swing," vaējant- "swinging;" cf. Skt. vej- "to tremble, wince."

The time required for the plane of a freely suspended → Foucault pendulum to complete an apparent rotation about the local vertical. It is given by T = 23.9344 / sin φ in hours, where φ represents the latitude of the place. For Paris it is 31h 47m 38s; for the poles it 23.9344 h and for the equator it is ∞ since the plane of pendulum does not turn.

→ pendulum; → day.

A hypothetical means of extracting energy from a rotating black hole. If a particle spirals into the ergosphere of a black hole in a direction counter to the rotation of the black hole, and if the particle then breaks up into two fragments inside the ergosphere, one of the fragments can escape with energy greater than the energy of the original particle.

Named after Roger Penrose, English physicist (1931-), who devised the process; → process.

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.