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

A systematic observational error due to the characteristics of the observer.

Personal, adj. of → person; → equation.

The sum total of the physical, mental, emotional, and social characteristics of an individual (Dictionary.com).

→ personal; → -ity.

1) To make → personal or → individual; specifically, to mark as the property of a particular → person.
2) Same as → personify.

→ personal; → -ize.

Tanumidan, from tanum, → person, + -idan, → -ize; tanumârdan, → personify.

1) The attribution of human nature or character to animals, inanimate objects, or abstract notions, especially as a rhetorical figure.
2) The representation of a thing or abstraction in the form of a person, as in art.
3) The person or thing embodying a quality or the like; an embodiment or incarnation (Dictionary.com).

Verbal noun of → personify.

1) To conceive of or represent as a person or as having human qualities or powers.
2) To be the embodiment or personification of (Merriam-Webster.com).

→ person + -ify, → -fy.

A body of persons employed in an organization or place of work (Dictionary.com).

From Fr. personnel (as contrasted with matériel), from O.Fr. personel, → personal.

Tanumgân, from tanum, → personal, + -gân multiplicity suffix.

1) The technique or art of drawing three-dimensional objects on a flat surface so that to give the right impression of their relative sizes and distances. A drawing so made.
2) Of, or pertaining to the art of perspective.

From M.Fr. perspective, from M.L. (ars) perspectiva "science of optics," from feminine of perspectivus "of sight, optical" from L. perspectus, p.p. of perspicere "to inspect, look through," from → per- "through" + specere "to look at," → prospect.

Pargâsmandi, from pargâsmand, from pargâs, from par-, → per-, + gâs, "to look at," → prospect, + -mand possession suffix, from Mid.Pers. -omand; O.Pers./Av. -mant; cf. Skt. -mant or -ik, → -ic.

To cause a small → deviation in the → behavior of a → physical system, e.g. in the → orbit of a planet.

O.Fr. perturber, from L. perturbare "to confuse, disorder, disturb," from per- "through" + turbare "disturb, confuse," from turba "turmoil, crowd," turbidus "muddy, full of confusion."

Parturidan, from par-, related to pirâ- (cf. Av. per- "to pass across, through") + turidan "to run away, be very much ashamed," tur "withdrawal, flight;" Lori, Laki tur "restive, disobedient," Laki turyâyen "to get angry, lose one's temper," probably cognate with L. turba, as above.

1) Any departure introduced into a steady state of a system. The magnitude is often assumed to be small so that the resulting terms in the dependent variables may be neglected. The term "perturbation" is therefore sometimes used as synonymous with "small perturbation."
2) Gravitational effect of a third body that causes an alteration in the orbit of a body going around its primary.
See also: → linear perturbation theory, → method of small perturbationsn → perturbation equation, → perturbation method, → primordial curvature perturbation, → scalar perturbation, → secular perturbation, → tensor perturbation, → vector perturbation.

Verbal noun of → perturb.

Any equation governing the behavior of a → perturbation.

→ perturbation; → equation.

Approximate method of solving a difficult problem if the equations to be solved depart only slightly from those of a problem already solved.

→ perturbation; → method.

A celestial body that causes a perturbation in the orbit of another body.

Agent noun of → perturb; → body.

A prefix denoting 10¹⁵.

Of unknown origin.

A combining form meaning "rock," "stone." Also, petri-, and petr- when before a vowel.

From Gk. petro-, combining form of petra "rock."

Sang "rock," → stone.

Natural mixture of liquid hydrocarbons and other organic compounds that include crude oil, refined products obtained from the processing of crude oil, and natural gas liquids.

M.L. petroleum literally "rock oil," from L. petra "rock," from Gk. → petro-, + oleum "oil."

Naft, from Mid.Pers. npt "moist, damp; naphtha," nmb "moisture," from which derives Mod.Pers. nam "humidity, moisture;" Av. napta- "moist," nabah- "cloud; sky;" cf. Skt. nábhas- "moisture, cloud, mist;" PIE base *nebh- "cloud, vapor, fog, moist, sky" (Gk. nephos "cloud, mass of clouds," nephele "cloud;" L. nebula "mist," nimbus "rainstorm, rain cloud;" O.H.G. nebul; Ger. Nebel "fog;" O.E. nifol "dark"). The link between "water, moisture" and "naphta" is suggested to be the natural gas or oil seepages surfacing through water. In fact many of the Zoroastrian fire-temples were located in areas which contained large petroleum leakages, such as those in Khuzestân and at Surakhany near Baku.

The branch of → geology that deals with → rocks: their classification, composition, structure, occurrence, and conditions of origin.

→ petro-; → -logy

An astrophysical source which accelerates → cosmic rays up to energies of several petaelectronvolts. For example, in the → Galactic center, cosmic ray → protons reach such energies. The source of such particles is a matter of research (→ HESS collaboration, 2016, Nature 531, 476).

PeVatron, from PeV (→ peta- + → electronvolt); + euphonic affix -a-; + → -tron.

A series of lines in the infrared spectrum of atomic hydrogen whose representing transitions between the fifth energy level and higher levels.

After August Herman Pfund (1879-1949), an American physicist and spectroscopist; → series.

A member of the class of stars in transition between → post-AGB and → white dwarf stars, with temperatures as high as 200,000 K, mean mass about 0.6 M_sun, and log g = 5.5-8. PG 1159 stars have no hydrogen or He I lines in their spectra, but do show weak He II lines and stronger lines of ionized carbon and oxygen. These stars are thought to be the exposed inner core of a star that has exploded as a → planetary nebula and is on its way to become a white dwarf. Also called → pre-degenerate star

Named after their prototype PG 1159-035, from the Palomar-Green Catalog of Ultraviolet Excess Stellar Objects (Green et al. 1986, ApJS 61, 305); → star.

A → logarithmic measure of → hydrogen ion concentration, originally defined pH = log₁₀ (1/[H⁺]), where [H⁺] is the concentration of hydrogen ions in → moles per liter of solution. The hydrogen ion concentration in pure water around room temperature is about 1.0 × 10^-7 moles. Therefore, a pH of 7 is considered "neutral," because the concentration of hydrogen ions is exactly equal to the concentration of → hydroxide (OH^-) ions produced by → dissociation of the → water. Increasing the concentration of hydrogen ions above 1.0 × 10^-7 moles produces a solution with a pH of less than 7, and the solution is considered → acidic. Decreasing the concentration below 1.0 × 10^-7 moles produces a solution with a pH above 7, and the solution is considered → alkaline or → basic. The neutral pH is different for each → solvent. For example, the concentration of hydrogen ions in pure ethanol is about 1.58 × 10^-10 moles, so ethanol is neutral at pH 9.8. A solution with a pH of 8 would be considered acidic in ethanol, but basic in water.

From Ger. PH, introduced by Danish biochemist S.P.L. Sørensen (1868-1939) in 1909, from P, for Ger. Potenz "power, potency," and H, symbol of → hydrogen.