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

A planet formation concept that concerns the → accretion of small objects of negligible gravitational mass (ranging from centimeters up to meters in diameter) onto large, gravitating bodies: → planetesimals, → protoplanets, or → planets. In a more narrow sense, pebble accretion is an accretion process where (gas) drag and gravity play major roles. Simply put, this means that the pebble has to be aerodynamically small and the planet to be gravitationally large (C. W. Ormel, in Formation, Evolution, and Dynamics of Young Solar Systems, p. 197, eds. M. Pessah, O. Gressel, Springer, 2017).

→ pebble; → accretion.

In astronomy, designating an object with special properties that deviates from others of its type.
Linguistically related terms: → particular, → special.

From L. peculiaris "of one's own (property)," from peculium "private property," from pecu "flock, farm animals, cattle," pecunia "money, property;" cf. Av. pasu-, fšu- "sheep;" Mid.Pers. pâh, pasvīk "cattle;" Mid./Mod.Pers. šu/ša in šupân/šabân "cattle keeper, shepherd;" Pers. dialects Laki and Tâti pas "sheep;" Skt. paśu- "cattle;" Goth. faihu "money, fortune;" O.E. feoh "cattle, money;" Ger. Vieh "cattle;" Lith. pekus "cattle;" PIE base *peku- "cattle."

Afd "peculiar; strange" (Dehxodâ), from Mid.Pers. afd, awd "peculiar, strange."

An irregular galaxy that has an abnormal shape (neither elliptical, spiral, nor lenticular) and/or has another unusual characteristic.

→ peculiar; → galaxy.

1) The true motion of a star with respect to the Local Standard of Rest. → proper motion.
2) The motion of a cosmological object other than the apparent recession caused by the expansion of the Universe.

→ peculiar; → motion.

A star with a spectrum that cannot be conveniently fitted into any of the standard → spectral classifications.

→ peculiar; → star.

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.