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

1) A small piece of material used to mend a tear or break, to cover a hole, or to strengthen a weak place.
2) A piece of material used to cover or protect a wound, an injured part, etc.
3) A small piece, scrap, or area of anything (Dictionary.com). → bald patch; → patchy turbulence.

M.E. pacche; of uncertain origin.

Pac, from Bašgaridi (Giroft) pac "patch; fragment," probably from *parka-, from *par- "piece" + diminutive/relation suffix -ka; cf. pâré "piece, part, portion;" parré "portion, segment (of an orange);" pargâlé "piece, portion; patch;" Kermâni pariké "portion, half;" Tabari perik "minute quantity, particle;" Lârestâni pakva "patch;" Borujerdi parru "patch;" (Fin Bandar Abbâs) park "patch;" (Tâti) pajina "patch, darn;" → part.

A → turbulence that is not continuous in space, but is separated by regions of stability and → laminar flow.

Patchy adj. of → patch; → turbulence.

A shallow dish-like crater with irregular, sometimes scalloped rims, on the surface of a planet.

From L. patera "abroad, shallow dish" (used for drinking, primarily in a ritual context).

1) A route, course, or track along which something moves.
2) A course of action, conduct, or procedure.
3) Math.: A continuous curve that connects two or more points.
4) In → graph theory, a → graph whose → vertices can be arranged in a sequence.

O.E. paþ, pæþ; cf. O.Fris. path; M.Du. pat; Du. pad; O.H.G. pfad; Ger. Pfad "path."

Pah "path, way," from O.Pers. paθi- "path, way;" Av. paθ-, variants paθi-, paθā-, pantay- (with conversion of -θ- to -h-, as in ciθra-/cehr, xšaθra-/šahr/šâh, vərəθraγna-/bahrâm, → Mars); Mid/Mod.Pers. pand "path, advice, counsel;" Khotanese pande "road, path;" Ossetic fœndœg "path, road;" cf. Skt. pánthā- "road, path, course;" Gk. patos "path, way," pontos "sea;" L. pons "bridge, path;" P.Gmc. *finthanan "to find;" E. find; PIE base *pent- "to go, to tread."
Râh, → way.

The path followed by an individual particle of fluid over an interval of time. It contrasts with the → streamline that represents an instantaneous picture of the motion of particles.

→ path; → line.

The path (up to 320 km wide) that the Moon's shadow traces on the Earth during a total solar eclipse.

→ path; → totality.

1) A person who makes or finds a way, especially through unexplored areas or fields of knowledge.
2) An airplane, or a person dropped from a plane, sent into a target area to illuminate the area for succeeding aircraft (Dictionary.com).
3) → LISA pathfinder.

→ path; → finder.

1) A regular or repetitive form, order, or arrangement; a distinctive form. → diffraction pattern; → interference pattern.
2) In the → density wave model, a region of enhanced stellar density (arm or bar) in the → Galactic disk. → pattern speed.

M.E. patron, from O.Fr. patron, from M.L. patronus "patron saint, lord, master, model, pattern," from pater "father."

Olgu "pattern," from Turkish ülgü "form, mold, model."

In models of → galactic structure, the → angular velocity of a → spiral arm or a → bar, assumed to be a pattern rotating as a solid body in the galaxy. Pattern speed, Ω_P , is one of the most important parameters of the → density wave theory responsible for the spiral arms. Pattern speed determines the location of the → corotation resonance.

→ pattern; → speed.

A quantum mechanical principle according to which no two identical → fermions can share the same → quantum state. Also known as → exclusion principle.

In honor of Wolfgang Pauli (1900-1958), Austrian theoretical physicist, who formulated the principle in 1925; → exclusion; → principle.

The Peacock. A → constellation in the → southern hemisphere, at about 19h 30m → right ascension, 65° south → declination. Abbreviation: Pav; genitive: Pavonis.

From L. pavo "peacock;" paupulo "peacock's sound;" Gk. taos "peacock;"

Tâvus, from Ar., ultimately from Gk. taos "peacock."

The round edible seed of a widely cultivated plant, Pisum sativum, of the legume family.

False singular from M.E. pease (plural pesen), from O.E. pise (West Saxon), piose (Mercian) "pea," from L.L. pisa, variant of L. pisum "pea," from Gk. pison "the pea."

Noxod "pea," from Mid.Pers. naxôd, naxvat "pea."

1) The normal, non warring condition of a nation, group of nations, or the world.
2) (often initial capital letter) An agreement or treaty between warring or antagonistic nations, groups, etc., to end hostilities and abstain from further fighting or antagonism.
3) A state of mutual harmony between people or groups, especially in personal relations.

From M.E. pes, pais, pees, from Anglo-Norman peis, pes, from O.Fr. pais "peace, reconciliation, silence," from L. pacem (nominative pax) "compact, agreement, treaty of peace, tranquility," ultimately from PIE root *pag- "to fasten."

Râman, related to râmeš "tranquility, rest," ârâm "quiet, peaceful," ârâmidan "to become calm, calmed, rest," Mid.Pers. râm "peace," râmenidan "to give peace, pleasure," râmišn "peace, pleasure;" Av. ram- "to stay, rest;" cf. Skt. ram- "to stop, stand still, rest, become appeased;" Gk. erema "quietly, gently;" Goth. rimis "rest;" Lith. rāmas "rest." + suufix -an.

The pointed top of a mountain or ridge. The pointed top of anything. → Gamow peak; → peak wavelength.

Perhaps from M.L.G. pék "pick, pike."

Setiq "summit, top," from *us-tig, from us-, → ex-, + tig "pointed," related to tiq "blade," tiz "sharp," tež, tej, tij; Mid.Pers. tigr, têz, têž "sharp," O.Pers. tigra- "pointed," tigra.xauda- "pointed helmet (epithet of Scythians)," Av. tiγra- "pointed," tiγray- "arrow," tiži.arštay- "with the pointed spear," cf. Skt. tikta- "sharp, pungent, bitter," tejas- "sharpness, edge, point or top of a flame;" PIE base *st(e)ig- "to stick; pointed." Cognates in other IE languages: Gk. stizein "to prick, puncture," stigma "mark made by a pointed instrument," L. in-stigare "to goad," O.H.G. stehhan, Ger. stechen "to stab, prick," Du. stecken, O.E. sticca "rod, twig, spoon," E. stick.

The → bolometric luminosity of a → supernova corresponding to the highest brightness in its → light curve. The peak luminosity occurs after the → supernova explosion; it is directly linked to the amount of radioactive ⁵⁶Ni produced in the explosion and can be used to test various explosion models. Following → Arnett's rule, one can derive the ⁵⁶Ni mass from the peak luminosity of a → Type Ia supernova.

→ peak; → luminosity.

The wavelength at which the radiant intensity of a source is maximum.

→ peak; → wavelength.

The pod or the enclosed edible seed of the plant, Arachis hypogaea, of the legume family: the pod is forced underground in growing, where it ripens (Dictionary.com). → box-peanut bulge.

From pea, → green pea galaxy + nut O.E. hnutu, akin to L. nux, → nucleus.

A secretion consisting mainly of calcium carbonate, CaCO₃, produced by various mollusks.

M.E. perle, from O.Fr. perle, M.L. perla of unknown origin.

Morvârid "pearl;" Mid.Pers. murwârid, murgârid; cf. Sogd. marγārit, marrγārt; Khotanese mrāhe. Gk. margarites "pearl" may be a loanword from Iranian.

A partially carbonized vegetable matter, usually mosses, found in bogs and used as fertilizer and fuel.

M.E. pete, of unknown origin.

Turb, from Fr. tourbe, from Germanic turba; cf. O.Fris. turf, O.H.G. zurba, Ger. Torf, O.E. turf, tyrf "slab of soil and grass," E. turf.

Geology: A → sedimentary particle that is between 4 and 64 mm in size. Pebbles are larger than → granules but smaller than → cobbles. Pebbles have typically been rounded by → abrasion during sedimentary transport (geology.com/dictionary).

From M.E. pibel, from O.E. *papol, *pyppel, *pæbbel, of unknown origin.

Rig, from Mid.Pers. rik "pebble, sand."