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

Of or pertaining to a particular person; individual; private. → personal equation.

→ person; → -al.

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) 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.

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 hypothetical → planet which once was postulated to have existed between the orbits of → Mars and → Jupiter and its destruction supposedly led to the formation of the → asteroid belt. The idea of such a hypothetical planet was first put forward by the German astronomer Heinrich Wilhelm Olbers (1758-1840).

In Greek mythology Phaeton was the sun god Helios. Phaeton tried to drive his father's solar chariot but crashed after almost setting fire to the whole earth.

The variation in brightness of a target as the phase angle (the angle between Sun and observer as seen from the target) varies between 0° and 180°. The directional distribution of reflected (or scattered) radiation. The phase angle is the supplement of the scattering angle (the angle between the incident ray and the emerging ray); in other words, the sum of the phase angle and the scattering angle is always 180° (Ellis et al., 2007, Planetary Ring Systems, Springer).

→ phase; → function.

Modulation in which the phase angle of a sine-wave carrier is caused to depart from the carrier angle by an amount proportional to the instantaneous magnitude of the modulating wave.

→ phase; → modulation.

A measure of the relative phase in the image as function of frequency. It is the phase component of the → optical transfer function. A relative phase change of 180°, for example, results in an image with the black and white areas reversed.

→ phase; → transfer; → function.

The changing of a substance from one phase to another, by → freezing, → melting, → boiling, → condensation, or → sublimation. Also known as phase transformation. A well known phase transition is the transition from → water to → ice. Phase transitions are often associated with → symmetry breaking. In water there is a complete symmetry under rotations with no preferred direction. Ice has a crystal structure, in which certain orientations in space are preferred. Therefore, in transition from water to ice the continuous rotational symmetry is lost.

→ phase; → transition.

→ Lunar phase.

→ phase; → Moon.

1) An occurrence, circumstance, or fact, in matter or spirit, which can be perceived by human senses. → physical phenomenon.
2) Philosophy: For Kant, a thing as it is apprehended by the human senses as distinguished from a noumenon, or thing-in-itself.

From L.L. phænomenon, from Gk. phainomenon "that which appears or is seen," from phainesthai "to appear," passive of phainein "to bring to light; to show," from PIE base *bhhā- "to shine;" cf. Skt. bhāati "shines, glitters;" Av. bā- "to shine, appear, seem," bāmya- "light, luminous, bright," bānu- "light, ray;" Mid.Pers. bâm "beam of light, splendor," bâmik "brilliant," bâmdâd "morning, dawn."

Padidé, noun from padid "manifest, evident, conspicuous, in sight," variant padidâr, from Mid.Pers. pad didâr "visible," from pad "to, at, for, in," evolved to bé "to; for; in; on; with; by" in Mod.Pers. (O.Pers. paity; Av. paiti "to, toward, in, at;" cf. Skt. práti, Gk. poti) + did past stem of didan "to see, regard, catch sight of, contemplate, experience" (O.Pers. dī- "to see;" Av. dā(y)- "to see," didāti "sees;" cf. Skt. dhī- "to perceive, think, ponder; thought, reflection, meditation," dādhye; Gk. dedorka "have seen").

A correlation between the peak brightness of → Type Ia supernovae and the decline rate of their → light curve (15 days after the maximum). The decline rate is also correlated to the width of the peak brightness of the supernova. The brightest events are the broadest in time and brighter SNe Ia decline more slowly than dimmer ones. Applying the Phillips relation reduces the dispersion in the light curves of Type Ia SNe thus making them precise distance indicators which can be observed over large distances.

Named after Mark M. Phillips (1951-), American astronomer (Phillips et al. 1993, ApJ 413, L105); → relation.

A hypothetical substance that, prior to the discovery of → oxygen, was thought to be released during → combustion. → phlogiston theory.

From New Latin, from Gk. phlogiston, neuter of phlogistos "inflammable, burnt up," from phlogizein "to set on fire, burn," from phlox "flame, blaze;" from PIE root *bhel- "to shine, burn."

Fložiston, loan from Fr, as above.