An Etymological Dictionary of Astronomy and Astrophysics

Symbol, π, for the ratio of the circumference of a circle to its diameter in Euclidean geometry; a fundamental mathematical constant, equal to 3.14159… π is an → irrational number
(Lambert, 1761) and also a → transcendental number (von Lindemann, 1882). The most accurate determination of π prior to the Scientific Revolution belongs to the Iranian mathematician Jamshid Kashani, who gave 16 correct decimal places in A.D. 1424. With the advent of → calculus and more recently the invention of powerful computers, the decimal representation of π has now been computed to more than 10¹² digits.

See also: The π notation, representing the first letter of the Gk. word περιμετρον → perimeter, was first used by the British mathematician William Jones (1675-1749) in 1706. Its use was generalized after its adoption by the Swiss mathematician Leonard Euler (1707-1783) in 1737; → number.

Same as → 61 Cygni and → Bessel’s star.

See also: Giuseppe Piazzi (1746-1826) was the first to notice the large → proper motion of the star, in 1804. His observations over a period of 10 years revealed the largest proper motion ever detected for any star at the time, leading him to baptize it the “Flying Star;” → fly; → star.

A series of → spectral lines of → singly ionized helium, observed in very hot → O-type and → Wolf-Rayet stars associated with transitions between the → energy level with → principal quantum number n = 4 and higher levels:

n = 4-5 (10124 Å), n = 4-7 (5412 Å), n = 4-9 (4541 Å), n = 4-9 (4522 Å), and n = 4-11 (4200 ˚). The 4-6 (6560 Å) and 4-8 (4859 Å) transitions were originally not included in this series because they coincided with the hydrogen → Balmer series of lines and were thus obscured.

See also: In honor of Edward C. Pickering (1846-1919), American astronomer and physicist; → series.

A prefix denoting 10^-12.

See also: From It. piccolo “small.”

The Painter’s Easel. A faint constellation in the southern hemisphere, at 5h 30m right ascension, 50° south declination. Its brightest star is of magnitude 3.2. Its second brightest star, → beta Pictoris, is famous for its → circumstellar disk of gas and dust. Abbreviation: Pic; genitive: Pictoris.

Etymology (EN): Pictor, short for Equuleus Pictoris “painter’s easel,” from L. pictor “painter,” from pingere “to make pictures.”

Etymology (PE): Negârgar “painter,” from negâr present stem of negâštan “to paint,” negâr “picture, figure,” from prefix ne- “down; into”
(O.Pers./Av. ni- “down; into;” cf.
Skt. ni “down,” nitaram “downward;” Gk. neiothen “from below;” E. nether; O.E. niþera, neoþera “down, downward, below, beneath,” from P.Gmc. *nitheraz;
Du. neder; Ger. nieder; PIE *ni- “down, below”) + gâr, from kar-, kardan “to do, to make” (Mid.Pers. kardan; O.Pers./Av. kar- “to do, make, build;” Av. kərənaoiti “he makes;” cf. Skt. kr- “to do, to make,” krnoti “he makes, he does,” karoti “he makes, he does,” karma “act, deed;” PIE base k^wer- “to do, to make”).

Any visible image, however produced. → photograph.

Etymology (EN): From L. pictura “painting,” from pictus, p.p. of pingere “to make pictures, to paint.”

Etymology (PE): Fartur “picture, image; reflexion, inversion” (Dehxodâ, Steingass); maybe from partow, → ray.

1. A portion of an object or of material, produced by cutting, tearing, or breaking the whole.
   

   2. An item forming part of a set.
      

   3. A written, musical, or artistic creation (OxfordDictionaries.com).

Etymology (EN): M.E. pece, peece, from O.Fr. piece, from V.L. *pettia, probably from Gaulish (cf. Welsh peth “thing;” Breton pez “piece”).

Etymology (PE): Teké “piece, patch.”

Denoting a → function that is defined on a sequence of → intervals or pieces. For example: |x| = -x for x < 0, x = 0 for x = 0, and x = x for x > 0.

See also: → piece, + -wise, → clockwise.

A function f(x) in an interval if :1) the interval can be divided into a finite number of pieces in each of which f(x) is continuous, and 2) the limits of f(x) as x approaches the boundary point of each piece are finite. In other words, a piecewise continuous function is one that is made up of a finite number of continuous pieces.

See also: → piecewise; → continuous; → function.

The property exhibited by some crystals (notably quartz) that develop an electric charge or potential difference across them when subjected to mechanical strain; and conversely produce mechanical forces when a voltage is applied to them in a suitable manner.

Etymology (EN): From piezo-, from Gk. piezein “to press tight” + → electric; → effect.

Etymology (PE): oskar, → effect; fešârbarqi pertaining to fešârbarq, from fešâr, → pressure, + barq, → electricity.

An assemblage of things laid or lying one upon the other (Dictionary.com).

Etymology (EN): M.E., from M.Fr. pile and directly from L. pila “pillar, mole of stone.”

Etymology (PE): Tal “heap; hill,” maybe related to Gk. tylos “a hard and thickened area on the skin, callus, lump,” tymbos “burial mound, grave, tomb;” Av. tuma- “fat;” L. tumere “to swell,” tumulus “raised heap of earth,” tumidus “swollen;” tumor “a swelling.”

An elongated structure often found at the interface between an → H II region and its associated → molecular cloud. Also called → elephant trunk. The most famous examples are the “pillars of creation” in the → Eagle Nebula, which are several → light-years in length. There are indications for star formation at the tips of the pillars. In general the pillars point like fingers toward the young → massive stars ionizing the nebula. Most of the mass is concentrated in the head which has a bright rim facing the young stars.

Etymology (EN): M.E. pillare, O.Fr. piler, from M.L. pilare, from L. pila “pillar, stone barrier.”

Etymology (PE): Sotun “pillar,” → column.

The component of a → planispheric astrolabe that is inserted in the back of the → mater. The pin enables the main parts of the instrument (the → alidade, the → rete, and the → rule) to rotate freely around the common center of the mater and the → tympanum (online museo galileo, VirtualMuseum).

Etymology (EN): M.E. pinne, from O.E. pinn “peg, bolt,” from L. pinna “a feather, plume.”

Etymology (PE): &ACIRC;sé, → axis.

The constriction of a current-carrying plasma column caused by its external self-magnetic field.

Etymology (EN): M.E. pinch, from O.Fr. pincier “to pinch,” possibly from V.L. *punctiare “to pierce,” from L. punctum “point,” and *piccare “to pierce.”

Etymology (PE): Penk “pinch, squeezing or compressing between the finger and thumb” (Dehxodâ), cf. (Tabari) pendik, pecelik, (Kermâni) perenju “pinch,” maybe related to panjé “the palm of the hand with five fingers; fist,” from panj “five,” 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.”

An → aberration of a → lens  → system in which → magnification increases with → distance from the → optical axis, whereby → horizontal and → vertical lines bend inward toward the → center of the → field. Opposite of → barrel distortion.

Etymology (EN): Pincushion, from pin, from M.E. pinne, O.E. pinn “peg;” cf. D. pin, Ger. Pinne; perhaps from L. pinna “feather, quill”

• cushion, M.E. cuisshin, O.Fr. coissin (Fr. coussin) a variant of V.L. *coxinum, either from L. coxa “hip, thigh,” or from L. culcita “mattress;” → distortion.

Etymology (PE): Cowlegi, → distortion; bâleštaki, adj. of bâleštak, diminutive of bâlešt, variant bâleš “cushion, pillow,”
Mid.Pers. bâlišn, bâlên “cushion, pillow;”
Av. barəiš- “pillow, cushion;” cf. Skt. barhis- “straw, a bed or layer of kusa grass strewed over the sacrificial ground.”

In a → planispheric astrolabe, a vane on an end of an → alidade with a hole, slot, or other indicator through which one can view a distant object. There may also be a pointer or pointers on the alidade to indicate a position on a scale.

Etymology (EN): Diminutive of L. pinna “feather, wing, fin;” + → -ule.

Etymology (PE): Mori (Biruni).

A child’s toy consisting of a wheel or leaflike curls of paper or plastic loosely attached by a pin to a stick, designed to revolve when blown by or as by the wind (Dictionary.com).

Etymology (EN): → pin; → wheel.

Etymology (PE): Ferferé “pinwheel,” of unknown origin.

An unstable nuclear particle of mass intermediate between that of a proton and an electron; also called π meson.

See also: From pi (meson) + → -on.

1. A long tube of metal, plastic, etc, used to conduct water, oil, gas, etc.
   

2. A device consisting of a tube used for smoking.

Etymology (EN): M.E., O.E. pipe “musical wind instrument; tube,” from V.L. *pipa “a pipe,” from L. pipare “to chirp, to peep,” of imitative origin (cf. It. pipa, Fr. pipe, Ger. Pfeife, Du. pijp).

Etymology (PE): 1) Lulé, → tube.
2) Pip loan from Fr., as above.

An extended complex of → molecular clouds in the constellation → Ophiuchus, apparently shaped like a smoker’s pipe, about 5° in size and located about 5° away from the → Galactic center. It has a mass of 10⁴ solar masses, lies at a distance of about 130 pc, and is among the closest molecular clouds to Earth. The Pipe Nebula includes a number of → dark nebulae, including Barnard 59, 65, 66, 67, 77, 244, and 256. It is of particular interest because of the almost complete lack of
→ star formation within it. This cloud is an extremely rare example of a relatively massive molecular cloud that may be in a state of evolution prior to the onset of significant star-forming activity.

See also: → pipe; → nebula.

1. A long tubular conduit or series of pipes used to transport crude oil, natural gas, water, etc., often underground and over great distances.
   

2. A channel or process along which something passes or is provided at a steady rate.

See also: → pipe; → line.

The Fishes. An extensive but faint constellation of the → Zodiac, representing a pair of fishes, located in the northern hemisphere, at 1h right ascension, 15° north declination. Abbreviation: Psc; genitive: Piscium.

Etymology (EN): L., plural of piscis “fish,” cognate with Goth. fisks, O.E. fisc.

Etymology (PE): Mâhi “fish,” from Mid.Pers. mâhik; Av. masya-; cf. Skt. matsya-, Pali maccha-.

The Southern Fish. A small constellation in the southern hemisphere, at 22h 30m right ascension, 30° south declination. Its brightest star, → Fomalhaut, has apparent visual magnitude 1.3. Abbreviation: PsA; genitive: Piscis Austrini.

Etymology (EN): L. piscis “fish,” cognate with Goth. fisks, O.E. fisc; austrinus “southern.”

Etymology (PE): Mâhi “fish,” → Pisces; daštari “southern,” → south.

A disk or cylindrical part tightly fitting and moving within a cylinder, either to compress or move a fluid collected in the cylinder, as air or water, or to transform energy imparted by a fluid entering or expanding inside the cylinder, as compressed air, explosive gases, or steam, into a rectilinear motion usually transformed into rotary motion by means of a connecting rod (Dictionary.com).

See also: From Fr. piston, from M.Fr. piston “large pestle,” from O.It. pistone “a piston,” from pestare “to pound,” from L.L. pistare, from pistare “to pound.”

The sensation of a sound frequency; the relative highness or lowness that we hear in a sound. A high pitch sound corresponds to a high frequency sound wave and a low pitch sound corresponds to a low frequency sound wave. In music, a sound that has a definite pitch is called a → tone. Sounds may be generally characterized by pitch, → loudness, and → quality.

Etymology (EN): M.E. picchen “to thrust, pierce, set;” maybe akin to pick.

Etymology (PE): Dong “voice, sound,” variants bâng, vâng, vang, zang, Tabari šong “cry;” related to vâž, → word.

A natural ore consisting mainly of → uranium oxide, U₃O₈, with small amounts of → radium, of which is the principal source. It usually contains some → lead and variable amounts of → thorium and → rare-earth elements.

See also: From Ger. Pechblende, from Pech “pitch” (from its black color) + Blende “a mineral.”

A → device used to → measure the → velocity of a flowing → fluid. The Pitot tube is used on → aircrafts to determine their → speed. It is also used to meaure water speed of a boat as well as liquid, air, and gas velocities in industrial applications. It is a small tube that has two holes on it. The front hole is placed in the airstream to measure the → stagnation pressure. The side hole measures the → static pressure. The difference between these pressures gives the → dynamic pressure, which can be used to calculate airspeed. See also the → Bernoulli equation.

See also: Named after the French inventor Henri Pitot (1695-1771), a hyraulic engineer; → tube.

The smallest useful element of image information.

See also: From pix, plural of pic, short for → picture + el, from → element.