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

The latest Epoch of the Tertiary Period, beginning about 5.3 million years ago and ending 1.6 million years ago.

From plio-, varaint of pleo-, from Gk. pleon "more," cognate with Pers. por, → full, + -cene from Gk. kainos "new, recent."

The British name of a group of seven stars (→ asterism) lying inside the Northern constellation → Ursa Major. Same as → Big Dipper.

M. E. plough, plouw, from O.E. ploh, plog "plow, plowland."

Haft barâdarân "the seven brothers," from haft "seven" (Mid.Pers. haft, Av. hapta, cf. Skt. sapta, Gk. hepta, L. septem, P.Gmc. *sebun, Du. zeven, O.H.G. sibun, Ger. sieben, E. seven; PIE *septm) + barâdarân, plural of barâdar "brother" (Mid.Pers. brad, bardar, O.Pers./Av. brātar-, cf. Skt. bhrátar-, Gk. phrater, L. frater, P.Gmc. *brothar; PIE base *bhrater- "brother").
Haftowrang, Mid.Pers. haptôiring, from Av. haptôiringa- "with seven marks," from hapto- "seven,"as above, + iringa- "mark," cf. Skt. linga- "mark, token, sign."

A small mass of lead or other heavy material, as that suspended by a line and used to measure the depth of water or to ascertain a vertical line (Dictionary.com). → plumb line.

M.E. plumbe, from O.Fr. *plombe, plomee "sounding lead," from L. plumbum "lead (the metal), lead ball," of unknown origin, related to Gk. molybdos "lead."

Gulé "ball, sphere," a variant of golulé, → bullet.

A cord with a weight attached to one end, used to verify a true vertical alignment or to find the depth of water.

→ plumb; → line.

Šâqul, variants šâhul, sâhul, probably from sahi + suffix -ul, variant -âl. The first element sahi "upright, right," variants (Tabari, Torbat-Heydariyeyi: šax) "right, upright, straight, level," colloquial Pers. šaq (o raq = râst) "upright, erect." For the second element → -âl.

A structure or form that is like a long feather. → polar plume.

From M.E., from O.Fr. plume, from L. pluma "feather, down," from PIE base *pleus- "feather, fleece."

Parr "feather," variant bâl "wing," Mid.Pers. parr "feather, wing," bâl; Av. parəna- "feather," Skt. parnam, cf. O.H.G. farn "fern," PIE pornom "feather."

1a) Act of plunging.
1b) The act of descending or dipping suddenly; (steep) fall, slide from vertical.
2) Geology: The vertical angle between the fold axis or any inclined line in a geologic structure and the horizontal plane.
3) To cast oneself, or fall as if cast, into water, a hole, etc.

M.E., from M.Fr. plung(i)er, from O.Fr. plongier "plunge, sink into; plunge into, dive in," from V.L. *plumbicare "to heave the lead," from L. plumbum "lead," → plumb.

1, 3) Širjé, probably deformation of sarjé, literally "head jump" (nose dive), from sar, → head, + jé, from jahidan, → jump.
2) Laxšé, noun from laxšidan "to slide," variant laqzidan.

1) Consisting of, containing, or pertaining to more than one thing.
2) Grammar: A form of nouns, pronouns, and verbs that refers to more than one thing or (in languages that recognize the dual form) more than two.

M.E., from O.Fr. plurel "more than one," from L. pluralis "of or belonging to more than one," from plus (genitive pluris) "more," → plus.

Bišâl, from biš "much, more; great," → plus, + -âl, → -al.

1) A state of society in which various religious, ethnic, racial, and political groups are allowed to thrive in a single society.
2) Philo.: A belief that there are more than two kinds of principles, as contrasted to the → dualism and → monism.

→ plural; → -ism.

The state or fact of being plural or numerous.

→ plural + → -ity.

1) (prep.) With the addition of.
2) (adj.) Additional; → positive.
3) (n.) An addition; a positive quantity; the → plus sign.

L. plus "more," cognate with Gk. polys "much," Pers. por, → full.

Bišan, from biš "much, more; great" + suffix -an, → minus. The first component from Mid.Pers. veš "more, longer; more frequently," related to vas "many, much" (Mod.Pers. bas); O.Pers. vasiy "at will, greatly, utterly;" Av. varəmi "I wish," vasô, vasə "at one's pleasure or will," from vas- "to will, desire, wish."

The symbol + indicating summation or a positive quantity. The sign is believed to be a shortened form of the L. word et denoting "and" which was the term for addition. The signs + and - first appeared in an arithmetic book by Johannes Widmann entitled Behennde und hübsche Rechnung, published in Leipzig in 1489.

→ plus; → sign.

A → dwarf planet in the → solar system which until 2006 was known as the 9th major planet. Pluto revolves around the → Sun in a highly elliptical orbit at a mean distance of 39.5 → astronomical units once every about 248 years. The orbit → eccentricity is 0.25 (compare with the Earth's 0.02) yielding a → perihelion distance of 29.66 → astronomical units and an → aphelion distance of 48.87 AU. Its → orbital inclination is 17 degrees, which is much higher than those of the other planets. Pluto's mass is 1.308 × 10²² kg, that is 0.00218 Earth mass (0.177 Moon mass), its equatorial radius ib 0.19 Earth radius, and its → rotation period is equal to 6.39 Earth days. It has five known → satellites, in order of distance from Pluto: → Charon, → Styx, → Nix, → Kerberos, and → Hydra. Pluto's radius is estimated to be about 1150 km (0.18 Earths). Pluto is smaller than seven of the solar system's satellites (the → Moon, → Io (Jupiter I) , → Europa, → Ganymede, → Callisto, → Titan, and → Triton). Pluto's surface has an estimated temperature of 37.5 K and is composed of more than 98% → nitrogen  → ice, with traces of → methane and → carbon monoxide.

In Roman mythology, Pluto is the god of the underworld and Judge of the dead, from L. Pluto, Pluton, from Gk. Plouton "god of wealth," literally "wealth, riches." Pluto was the son of Saturn. The alternative Gk. name is Hades.

A → radioactive → chemical element, symbol Pu. → Atomic number 94; → mass number of most stable isotope 244; → melting point 640 °C; → boiling point 3,235 °C. It was first synthesized in 1940 by American chemists Glenn T. Seaborg, Edwin M. McMillan, Joseph W. Kennedy and Arthur C. Wahl in the → nuclear reaction: ₉₂U²³⁸ + ₀n¹→ ₉₃Np²³⁹ + β^- (23.5 minutes) → ₉₄Pu²³⁹ + β^- (2.36 days). The → half-life of ₉₄Pu²³⁹ is 2.44 × 10⁴ yr. Plutonium-239 is a → fissile isotope.

The name derives from the planet → Pluto. It was selected because it is the next planet in the solar system beyond the planet → Neptune and the element plutonium is the next element in the → periodic table beyond → neptunium.

To trespass, especially on another's game preserve, in order to steal animals or to → hunt; to take game or fish illegally (Dictionary.com).

M.E., from M.Fr. pocher "to thrust, poke," from O.Fr. pochier "poke out, gouge, prod," related to poke (v.), from a Germanic source (compare M.H.G. puchen "to pound, beat, knock," Ger. pochen, Middle Dutch boken "to beat") related to poke (v.).

Beškaridan, from beškar(d), bišgar(d) "hunter, fowler; chase; game; place for hunting," variant of šekâr, → hunt.

A person who trespasses on private property, especially to catch fish or game illegally (Dictionary.com). See also → hunter.

→ poach; → -er.

The illegal taking of wildlife, in violation of local, state, federal or international law.

→ poach; → -ing.

The constant 2.512, which is the 5th → root of 100 (2.512⁵ = 100); the ratio between two successive stellar → magnitudes.

→ Pogson's relation; → ratio.

The equation that expresses the → magnitude  → difference between two objects in terms of the → logarithm of the → flux  → ratio:
I₁/I₂ = 2.5^{(m₂ - m₁)}, or
m₂ - m₁ = 2.5 log(I₁/I₂),
where m is → apparent magnitude, I flux, and log the logarithm to base 10.

Named after Norman Robert Pogson (1829-1891), the English astronomer, who introduced the magnitude scale in 1856; → relation.

In an → isolated system, any initial state will occur again in the course of the → evolution of the system over a sufficiently long but finite → time.

→ Poincaré sphere; → recurrence; → theorem.

A representation that permits an easy visualisation of all different states of → polarization of a vector wave. The equator represents → linear polarization; the north pole corresponds to right-circular and the south pole to left- → circular polarization.

Named after Henri Poincaré (1854-1912), French mathematician and theoretical physicist, and a philosopher of science; → sphere.