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

Color created by mixing light rays of different colors. Combining all the color rays of light results in white light. See also → subtractive color.

→ additive; → color.

1) A visual sensation produced in the brain when the eye views various wavelengths or frequencies of light.
2) Short for → color index.
3) A property of → quarks required to distinguish the three basic quarks of which → baryons are composed. In all → hadrons, the quarks (red, green, blue) are combined in such a way as to yield a colorless overall particle.

From M.E. colour, from O.Fr. colur, from L. color "color, hue," from Old L. colos "a covering," from PIE *kel-os- "that which covers," from *kel- "to cover, conceal."

Rang, from Mid.Pers. rang "color" (abrang "splendor"), related to Mod.Pers. razidan "to color," raxš "a mixture of red and white," also the name of Rostam's horse (loan from Sogd.?), awrang "glory, beauty, throne;" Kurd. raš "black;" cf. Skt. raj- "to color, to become red;" Gk. rezein "to color;" PIE base *(s)reg- "to color, paint" (Cheung 2007).

In the → standard model of particle physics, a property possessed by → quarks and → gluons that determine rules for how these particles may interact in the context of → quantum chromodynamics. Color charge is analogous to electromagnetic charge, but it comes in three types rather than two, which results in a different type of force, the → strong interaction. There are three pairs of colors and anti-colors, named red (anti-red), green (anti-green), and blue (anti-blue). The terminology has nothing to do with visible color. It is only a word that is used to designate three independent types of the strong charge characteristic.

→ color; → charge.

The difference between the observed → color index of a star and the intrinsic color index corresponding to its → spectral type. It indicates the modification brought to a color index by the → interstellar absorption.

→ color; excess, M.E., from O.Fr., from L. excessus "departure, going beyond," p.p. excedere "to depart, go beyond," from → ex- "out" + cedere "to go, yield."

Fozuni, from afzuni "excess," afzuni kardan "to exceed bounds," → add; → color.

The difference between the → apparent magnitude of a star measured at one standard wavelength and the apparent magnitude at another longer, standard wavelength, allowing the quantitative measure of a star's color.

→ color; → index.

The temperature of that black-body which has the same spectral energy distribution in a limited spectral region, as the object under study has.

→ color; → temperature.

Empirical mathematical transformation applied to the observed magnitudes in order to convert them into a standard system, or into a different system.

→ color; → transformation.

A diagram based on two photometric colors usually representing the same class of astronomical objects.

→ color; → diagram.

Fr.: diagramme couleur-couleur

Same as → color-color diagram.

A form of → Hertzsprung-Russell diagram in which the luminosity is the vertical axis and the → color index the horizontal axis.

→ color; → luminosity, → diagram.

A form of → Hertzsprung-Russell diagram in which the visual absolute magnitude M_v is the vertical axis and the → color index the horizontal axis.

→ color; → magnitude, → diagram.

The measurement and definition of unknown colors in terms of standard colors.

→ color; → -metry.

In imaging technique, assigning color to black and white images to differentiate features or convey information. → true color.

→ false; → color.

A photometric system which uses five filters, from ultraviolet to the red part of the visual spectrum: U, B, V, R and I.

→ five; → color; → system.

A → color not affected by → extinction.

→ intrinsic; → color.

The arrangement of the seven colors of the rainbow on a disk. When the disk rotates very fast, the eye cannot distinguish between individual colors and the disk is perceived as white. This apparatus demonstrates the discovery made by Newton (Opticks, 1704) that light is composed of seven colors.

→ Newton; → color; → wheel.

Color produced by mixing pigments rather than light. Mixing all of the subtractive colors together results in the color black. See also → additive color.

→ subtractive; → color.

A graph on which two color indices such as B-V and U-B are plotted, one along each axis, for a sample of stars or other objects, such as stars.

→ two; → color; → diagram.