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

A → negatively charged → ion or → radical. Anions in a liquid subjected to electric potential are attracted toward the → anode. See also → cation.

From Gk. anienai "to go up," from an-, from → ana- "up," + -i-, from ire, eo "to go, walk," cf. Pers. ây-, → assembly, + -on, as in → ion.

In an imaging system, the dependence of its performance on field angle. In other words, the spatial variability of the → point spread function for off-axis sources.

→ an- + → isoplanatism.

The departure from → isoplanicity.

→ an-; → isoplanicity.

Describing a medium in which certain physical properties are different in different directions.

→ anisotropy; → -ic.

A solution to Einstein's theory of → general relativity that is spatially homogeneous but allows for rotation and/or shear. See also → Bianchi cosmological model.

→ anisotropic; → homogeneous; → cosmological; → model.

A variation in a property with direction, e.g. → cosmic microwave background anisotropy, → dipole anisotropy.

From → an-, privative prefix, + → isotropy.

1) (in humans) The joint between the foot and the leg, in which movement occurs in two planes.
2) The corresponding joint in a quadruped or bird; hock (Dictionary.com).

M.E. ankel, enkel, cognate with M.L.G., Du. enkel, O.H.G. anchal, enchil, O.Norse okkul.

Quzak, from quz, variant of kuž "humped," → convex.

The process in which the entire → mass of → two colliding → particles, one of → matter and one of → antimatter, is → converted into → radiant energy in the form of → gamma rays. See also → annihilation operator.

L. annihilatus, p.p. of annihilare "to reduce to nothing," from ad- "to" + nihil "nothing," from ne- "not" + hilum "small thing, trifle"

Nâbudi, from nâ- "not" + bud "to be, exist," from budan "to be, exist" + -i noun forming suffix.

In → quantum field theory, the operator that lowers → eigenstates one → energy level, contrarily to the → creation operator.

→ annihilation; → operator.

To make known publicly or officially; proclaim; give notice of (Dictionary.com).

M.E., from M.Fr. anoncer, O.Fr. anoncier "announce, proclaim," from L. annuntiare, adnuntiare "to announce, relate," literally "to bring news," from → ad- "to" + nuntiare "relate, report," from nuntius "messenger."

žâyidan, from prefix â- + Sogd., Munji žây- "to speak, to say," Yaghnobi žoy- "to read, sing," Yazghulami γay- "to call," Pers. (prefixed) afqân "lamentation, groaning;" Av. gā- "to sing," pairi.gā.vacah- "who sings the words around," bərəzi.gāθra- "singing high," gāθə- "song, gāthā;" cf. Skt. gā- "to sing;" O.Russ. gajati "to croak (ravens)"; Lith. giedoti "to sing" (Cheung 2007).

Covering the period of a year; occurring or happening every year or once a year.

Annual, from M.Fr. annuel, from L.L. annualis, blend of L. annuus "yearly," from annus "year" and L. annalis "yearly," from annus "year," from PIE *atnos, from *at- "to go" (Skt. a'tati "he goes, wanders").

Sâlâné, from sâl, → year, + âné "-ly".

The apparent, small displacement in position of a star during the year due to the → aberration of starlight. It depends on the → celestial latitude, and its maximum value is about 20''.50. See also → constant of aberration; → aberration orbit.

→ annual; → aberration.

→ annual motion.

→ annual; → apparent; → motion.

An irregularity in the Moon's orbit, which can amount to 11 degrees in a period of one year. It results from the Sun's disturbing effect on the motion of the Moon due to varying distance between them.

→ annual; → equation.

The annual apparent motion of the → Sun in the sky with respect to → fixed stars along the path called → ecliptic. The apparent annual motion is due to the → Earth's → revolution about the Sun. In the course of this motion, the Sun appears to shifts about 1° eastward per day.

→ annual; → motion.

The difference in position of a star as seen from the → Earth and → Sun, i.e. the angle subtended at a star by the mean → radius of the Earth's orbit around the Sun. Same as → heliocentric parallax. Because the Earth revolves around the Sun, we observe the sky from a constantly moving position in space. Therefore, we should expect to see an annual effect, in which the positions of nearby objects appear to oscillate back and forth in response to our motion around the Sun. This does in fact happen, but the distances to even the nearest stars are so great that we need to make careful observations with a telescope to detect it. The annual parallax of the nearest star, → Proxima Centauri, is 0.762 arcsec, which is too small for our → acuity of vision.

→ annual; → parallax.

Generally, the variation of a quantity over a year. In particular the yearly change in the right ascension or declination of a star, produced by the combined effects of the precession of the equinoxes and the proper motion of the star.

→ annual; → variation.

(Especially of laws or other established rules, usages, etc.) to make void or null; abolish; cancel; invalidate (Dictionary.com).

M.E., from O.Fr. anuller, from L.L. annullare "to make to nothing," from L. → ad- "to" + nullum, neuter of nullus "nothing," → null.

Ânulidan, from prefix â- + nul, → null, + -idan infinitive suffix.

Having the form of a → ring.

From Fr. annulaire or directly from L. annularis "pertaining to a ring," from annulus, diminutive of anus "ring."

Halge-yi, halqevâr, adj. from halqé, → ring.

A solar eclipse in which the Moon is close the → apogee and is, therefore, too small to cover the whole disk of the Sun, leaving a visible edge or ring of sunlight. An annular eclipse can last for 12m 30s at the most. See also → total eclipse.

→ annular; → eclipse.