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

A group of persons acting or working together.

M.E. crewe "augmentation, reinforcement, body of soldiers," from M.Fr. crue, from O.Fr. creue "an increase, recruit, military reinforcement," from p.p. of creistre "grow," from L. crescere "grow, arise," → crescent.

Koran, variants korand, korang "a troop, a circle of people" (Dehxodâ).

In radio astronomy, the process performed by a → cross correlator or the result of the process.

→ cross; → correlation.

In radio interferometry, a device that multiplies together the signals received by each pair of antennas in an array and performs several operations on the signal (filtering out the noise added to the signal by the receiver electronics, correcting for the Doppler shift and geometric delay due to the position and motion of the antennas). The correlated signal, corresponding to the spatial frequency given by the distance between the two antennas, is then combined with the other spatial frequency to reconstruct the map of the source.

→ cross; → correlator.

Reference from one part or element of a book or data catalog to something in another for further information.

→ cross; → reference.

The geometric framework to which a crystal may be referred and the arrangement of atoms or electron density distribution relative to that framework, usually determined by X-ray diffraction measurements.

→ crystal; → structure.

An arrangement and interrelationship of parts that is of → crystalline nature.

→ crystalline; → structure.

1a) Enlightenment and sophistication acquired by a person or society through education, arts, letters, manners, and scholarly pursuits.
1b) The beliefs, customs, practices, and social behavior of a certain nation, people, or period.
2a) The growing of biological material (such as plants, microorganisms, animal tissue) for scientific study, medicinal use, etc.
2b) The product or growth resulting from such cultivation.

M.E., from M.Fr. culture from L. cultura "cultivation, agriculture; care; honoring," from p.p. stem of colere "to till, cultivate; inhabit; maintain; cherish, honor;" PIE *k^wel- "to move around;" cf. Av. car- "to move, go, walk," carāni "I would go," carāt "he would go;" Mid.Pers. car- "to pasture, graze," carag "pasture, grazing; flock;" Mod.Pers. caridan "to graze;" Skt. car- "to move, go, walk;" Gk. pelomai "to move."

1) Farhang "culture, education; dictionary," related to farhixtan "to educate," âhanjidan "to draw up;" Mid.Pers. frahang "education, instruction; knowledge," frahixtan, frahanjidan "to educate;" Av. fraθang- "to drive forward, to drive to," from frā-, fra- "forward, forth," → pro-, + θang-, θanj- "to draw, to pull."
2) Kešt past stem of keštan, variants kâštan, kâridan "to cultivate, to plant;" Mid.Pers. kištan, kâridan "to sow, plant; to make furrows;" Av. kar- "to strew seed, cultivate," kāraiieiti "cultivates;" cf. Skt. kar- "to scatter, strew, pour out."

The highest temperature for a given → ferromagnetic substance above which the → magnetization is lost and the substance becomes merely → paramagnetic. The Curie temperature of iron is about 1043 K and that of nickel 631 K.

Named after the French physicist Pierre Curie (1859-1906), a pioneer in magnetism, crystallography, and radioactivity. In 1903 he received the Nobel Prize in Physics with his wife Marie Curie (1867-1934, née Maria Skłodowska), and Henri Becquerel (1852-1908); → temperature.

Any steady movement of material in space. In particular, any movement of electric charge. → stream; → flow; → flux.

From O.Fr. corant "running," pr.p. of courre "to run," from L. currere "to run," from PIE *kers- "to run" (cf. Gk. -khouros "running," Lith. karsiu "go quickly," O.N. horskr "swift," Welsh carrog "torrent").

Jarayân from Ar.

The → Universe at the → redshift z = 0.

→ current; → cosmological; → epoch.

The electric current per unit of cross-sectional area perpendicular to the direction of current flow. It is a vector quantity and represented by symbol J. Electric current density is usually expressed in amperes per square meter.

→ current; → density

A measure of the amount by which a curve, a surface, or any other manifold deviates from a straight line, a plane, or a hyperplane. In particular, The reciprocal of the radius of the circle which most nearly approximates a curve at a given point.
See also:
→ curvature constant, → curvature of space-time, → field curvature, → primordial curvature perturbation.

From L. curvatura, from curvatus, p.p. of curvare "to bend," from curvus "curved," → curve.

Xamidegi, from xamidé "curved," from xamidag "curved" + noun suffix -i.

A parameter occurring in the → Friedmann equations of → general relativity describing the geometry of → space-time. A spatially → open Universe is defined by k = -1, a → closed Universe by k = + 1 and a → flat Universe by k = 0. See also the → Robertson-Walker metric. See also → curvature of space-time.

→ curvature; → parameter.

According to → general relativity, → space-time is curved by the presence of → matter. The curvature is described in terms of → Riemann's geometry. In → cosmological models three types of curvature are considered: positive (spherical, → closed Universe), zero (Euclidean, → flat Universe), and negative (hyperbolic, → open Universe). See also → curvature constant.

→ curvature; → space-time.

The frequency with which a → non-relativistic particle of charge q and mass m turns in a cyclotron with → uniform magnetic field B. The equality of the → centripetal force to the → Lorentz force leads to the expression: by: f_cycl = qB/2πm. For → relativistic case, the frequency is smaller and is called → synchrotron frequency.

→ cyclotron; → frequency.

Referring to the planet Venus.

From Cythera, in Gk. mythology another name of Aphrodite (Roman equivalent Venus), goddess of love and beauty, since she was believed to emerge from the Mediterranean island Cythera.

Nâhidi referring to Nâhid, planet Venus, Mid.Pers. Anahid "immaculate, unstained," goddess of pure waters and fertility, from Av. arədvi-sûra-anâhita, from arədvi- "increasing, rising," + sûra- "strong, powerful" (Skt. śūra- "valient, courageous") + anâhita "unstained," from an- negation prefix + âhita "spotted."

1) To be courageous enough to try to do something.
2) A challenge, especially to prove courage.

M.E. durren, from O.E. durran "be bold enough, have courage" (to do something); cf. O.Norse dearr, O.H.G. giturran, Gothic gadaursan, from PIE root *dhers- "bold" source also of O.Pers. darš-, as below.

Daršidan, from O.Pers. darš- "to dare," Av. darš- (prefixed *upa- in upadarəš- "to dare"); cf. Khotanese darv- "to dare;" Baluci durrit/durr- "to take courage;" Skt. dhars "to venture;" Gk. thrasus "bold;" Goth. ga-daursan "to venture;" E. "to dare;" PIE *d^hers- "to attack, venture, dare" (Cheung 2007).

Current generated in an electronic detector by thermal effects, even in the absence of input signal. In a → CCD detector, the current rises from thermal energy within the silicon lattice comprising the CCD. These electrons are captured by the CCD's potential wells and counted as signal. → dark current noise.

→ dark; → current.

In a → CCD detector, statistical fluctuation of the → dark current, equal to the square root of the dark current. CCDs can be cooled either with thermoelectric coolers or liquid nitrogen to reduce this effect. Ideally, the dark current noise should be reduced to a point where its contribution is negligible over a typical exposure time.

→ dark; → current; → noise.

A → CCD frame obtained with closed → shutters in the absence of any light source, in order to estimate the → dark current of the → detector.

→ dark; → exposure.