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

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 technique in spectroscopy which uses a combination of several dispersive elements (prisms in series or a grism) before focusing the light on the primary disperser, usually a grating, in order to achieve high spectral resolutions.

→ pre-; → dispersion.

The interval with which a rotating body precesses. The precession period of the Earth is 25,770 years. For a → spinning top it is given by: T_p = (4π²I)/(mgrT_s), where I is the → moment of inertia, m the mass of the top, g gravity, r the distance between the center of mass and the contact point, and T_s is the spinning period of the top.

→ precession; → period.

In cosmological models, the phenomenon that is supposed to seed the → cosmic microwave background anisotropies and the structure formation of the Universe.

→ primordial; → curvature; → perturbation.

A mechanism predicted by theoretical models of → supernova explosion in the case when the → supernova shock breaks through the outer edge of the collapsing → iron core before losing all of its energy (through → photodisintegration of the iron nuclei) and manages to expel the stellar envelope. Compare with → delayed supernova explosion.

→ prompt; → supernova; → explosion. See also → delay.

Belonging or pertaining exclusively or distinctly to a person, thing, or group. → proper mass; → proper motion; → proper time.

M.E., from O.Fr. propre, from L. proprius "one's own."

Saré "pure; principal."

A distance between two nearby events in the frame in which they occur at the same time. It is the distance measured by a ruler at the time of observation. Hence, for a cosmological time t, D_proper = D_C . a(t), where D_C is the → comoving distance, and a(t) is the → scale factor. In the present epoch a = a(t_obs) = 1, and D_proper = D_C.

→ proper; → distance.

Same as → rest mass.

→ proper; → mass.

The apparent motion of a star across the sky (not including a star's parallax), arising from the star's velocity through space with respect to the Sun. Proper motion is usually tabulated in star catalogs as changes in right ascension and declination per year or century. See also: → proper motion distance.

→ proper; → motion.

The distance derived from the → proper motion of an object. If an object has a known → transverse velocity  u, and has an observed angular motion of dθ/dt, then the proper motion distance is defined as: d = u/(dθ/dt).

→ proper; → motion; → distance

Of two sets A and B, the set A if it is contained in B (A ⊂ B) but is not equal to B (A ≠ B).

→ proper; → subset.

In general relativity, the time as measured on a clock that travels with the observer in the same system. An accelerated clock will measure shorter time intervals between events than a non-accelerated clock between the same events. → twin paradox.

→ proper; → time.

1) General: An essential or distinctive attribute or quality of a thing.
2) Physics: A quantity, such as length, mass, pressure, temperature, or volume, that relates to the state of a system and can be expressed in numbers obtained from well-defined measurement operations.

From M.E. propriete "ownership, something owned, one's own nature," from M.Fr. propriété, from L. proprietas "ownership, property, propriety," literally "special character," noun of quality from proprius "one's own, special."

Dârâk "thing owned," from dâr present stem of dâštan "to have, to possess" + -âk (on the model of xorâk, pušâk, kâvâk). The first element dâštan, from Mid.Pers. dâštan, O.Pers./Av. root dar- "to hold, keep back, maintain, keep in mind;" Skt. dhr- "to to hold, keep, preserve," dharma- "law;" Gk. thronos "elevated seat, throne;" L. firmus "firm, stable;" Lith. daryti "to make;" PIE *d^her- "to hold, support."