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

Gradient of apparent magnitude with air mass.

→ extinction; → coefficient.

In → photometric calibration, the correction for energy loss undergone by radiation due to the → atmospheric extinction. Extinction correction is done using → standard stars observed at different → airmasses.

→ extinction; → correction.

A graph representing the variation of the → interstellar extinction against → wavelength. Usually it displays the → normalized values of extinction as a function of (the → inverse) of the wavelength (in → microns). See, e.g., Sandage & Mathis, 1979, Ann. Rev. Astron. Astrophys. 17, 73.

→ extinction; → curve.

Stars specifically observed at selected air masses in view of determining the atmospheric extinction coefficients.

→ extinction; → star.

The geological process leading to the formation of → faults.

Verbal noun, → fault.

The process or instance of adapting a mathematical curve to data points.

Verbal form of → fit.

The discrepancy between the mathematical curve and data points. → fit.

→ fitting; → error.

A type of → equatorial mounting consisting of a two-pronged fork, which forms the → polar axis, with the → telescope pivoted between the prongs of the fork on a → declination axis.

→ fork; → mounting.

The process of preparing a hard disk or other storage medium for use by an operating system. Before a hard disk can be used, it needs to be formatted so that it will be able to store files and applications.

→ format; → -ing.

A population of → substellar objects which are not bound to stars; they are detected in young star clusters. Their masses, estimated from their fluxes, is several Jupiter masses, lower than those of → brown dwarfs. Their formation is not yet explained. Among the envisaged possibilities: 1) These objects form like stars, from protostellar core collapse and subsequent accretion; 2) they form as low-mass members of small groups, and are ejected from the group; 3) they form like planets within circumstellar disks of higher-mass objects, but are ejected either due to internal dynamics or external interactions.

→ free; floating, from M.E. float, from O.E. flotian "to float" (cf. O.N. flota, M.Du. vloten); → object.

Barâxt, → object; šenâvar "that swims, floats," from šenâ "swimming;" Mid.Pers. šnâz "swim," šnâzidan "to swim;" Av. snā- "to wash, swim;" cf. Skt. snā- "to bathe, to wash;" L. nare, natare "to swim" (Fr. nage, nager, natation; Sp.nadar, natacion).

An equatorial mounting in which the declination axis is at the end of the polar axis, which is on top of a pier to raise the telescope to a convenient height.

German, from L. Germanus, maybe of Gaulish (Celtic) origin, perhaps originally meaning "noisy" (cf. O.Ir. garim "to shout") or "neighbor" (cf. O.Ir. gair "neighbor"); → mounting.

Barnešând, → mounting; Âlmâni "German," from Âlmân, from Fr. Allemand "German," from P.Gmc. *Alamanniz, probably meaning "all-man" and denoting a wide alliance of tribes. Alternatively, perhaps meaning "foreign men," cognate with L. alius "the other."

Same as → diffraction grating.

M.E. grating, M.L. grata "a grating," variant of crata, from crat-, stem of cratis "wickerwork."

Turi, from tur "fishing net, net, snare," variants târ "thread, warp, string," tâl "thread" (Borujerdi dialect), cognate with tanidan, tan- "to spin, twist, weave" (Mid.Pers. tanitan; Av. tan- to stretch, extend;" Skt. tan- to stretch, extend;" tanoti "stretches," tantram "loom;" tántra- "warp; essence, main point;" Gk. teinein "to stretch, pull tight;" L. tendere "to stretch;" Lith. tiñklas "net, fishing net, snare," Latv. tikls "net;" PIE base *ten- "to stretch").

The angle between the incident optical beam and the normal to the grating. It is the angle to which the grating must be set to place the desired wavelength at the center of the detector.

→ grating; → angle.

The measure of the light intensity diffracted from a grating.

→ grating; → efficiency.

One of thousands of long, narrow indentations in the surface of a → diffraction grating.

→ grating; → groove.

A hypothetical force-carrying particle predicted by supersymmetry theories. The gravitino's spin would be 1/2; its mass is unknown.

From gravit(on) + (neutr)ino.

An experiment performed in 1971 using four atomic → cesium clocks transported in jet airplanes eastward and westward around the Earth to verify the → time dilation predicted by the theory of → special relativity.

J.C. Hafele and R. E. Keating, 1972, Science 177, 166; → experiment.

1) The process whereby a system's temperature increases. → warming.
2) A device or system for supplying heat, especially central heating, to a building; the heat supplied.

→ heat; → -ing.

The last visible setting of a star below the western horizon just after sunset entering into a conjunction with the Sun.

→ heliacal; → setting.

A → diffraction grating produced from a series of constructive → interference fringes. The fringes, whose intensities vary in a sinusoidal pattern, correspond to the grooves of the grating. They are recorded on a photosensitive substrate and subsequently treated using a chemical procedure. Since the grooves are created by the interference of light, such a grating is free from the random and periodic errors present in → ruled gratings.

→ holographic; → grating.