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

1) An apparently hollow formation in the structure of an astronomical object, for example a sizable hole on the surface of a → molecular cloud created by → ultraviolet photons of a → massive star.
2) In a semiconductor laser, two reflective parallel edges forming a resonator that amplifies the light through stimulated emission.

From M.Fr. cavité, from L.L. cavitas "hollowness," from L. cavus "hollow."

Kâvâk, related to verb kâvidan (kâftan) "to dig; to examine, investigate," cf. L. cavus "hollow" (E. derivatives: cavity, concave, cave, excavate), Gk. koilos "hollow," Armenian sor, PIE *kowos "hollow."

→ charge-coupled device.

Short for → charge + coupled, from → couple, + → device.

A CCD detector having two dimensions.

→ CCD; → array.

→ charge-coupled device.

→ CCD; → detector.

One of a series of astronomical images obtained using a CCD detector in particular for calibration purposes.

→ CCD; → frame.

In a → CCD detector, the ratio of the initial number of electrons in a → pixel to the final number of → analog-to-digital units (or counts) reported by camera software. For example, a gain of 1.8 e-/count means that the camera produces 1 count for every 1.8 recorded electrons.

→ charge-coupled device (CCD); → gain.

A mechanical device of a CCD camera that controls the duration of a an exposure, as by opening and closing to allow the stellar light to expose the CCD detector.

Shutter, from to shut, from O.E. scyttan from W.Gmc. *skutjanan + → -er.

A → cosmological model that attributes the formation of structures in the → early Universe to an exotic particle (→ cold dark matter) which was → non-relativistic at the time of → decoupling. According to this model, CDM began clumping together soon after the → Big Bang, while the → baryonic matter was still coupled with the → photons, and prevented to condense. Smaller → clumps of dark matter merged to form larger and larger clumps, and when the normal visible matter had decoupled from the photons, at the → recombination era (380,000 years after the Big Bang), it collapsed onto these dark matter clumps. In this way, the dark matter clumps acted as seeds for galaxy formation.

→ cold; → dark; → matter; → theory.

An often temporary cessation of hostilities during wartime for a specific purpose. It may be unilateral or bilateral.

From cease from O.Fr. cesser "to come to an end, stop," from L. cessare "to cease, go slow, be idle," + → fire.

Âtašbas, from âtaš, → fire, + bas, from bas kardan "to stop, end; leave."

Of or relating to the sky or visible heavens.

M.E., from O.Fr., from M.L. celestialis, from L. cælestis "heavenly," from cælum "heaven, sky."

Âsmâni related to âsmân, → sky.

The Earth's axis extended to the → celestial pole.

→ celestial; → axis.

→ astronomical object.

→ celestial; → body.

Any system of coordinates used to define a point on the celestial sphere (zenith distance, altitude, celestial latitude, celestial longitude, etc.).

→ celestial; → coordinates.

An imaginary great circle on the sky half-way between the → celestial poles. It is the projection of the → equator of the Earth on the sky.

→ celestial; → equator.

A small globe representing the celestial sphere, on which the apparent positions of the stars are indicated.

→ celestial; → globe.

A great circle on the → celestial sphere having a plane that passes through the center of the Earth at a right angle to the line formed by an observer's → zenith and → nadir.

→ celestial; → horizon.

Angular distance → north or → south measured from the → ecliptic to a → celestial object.

→ celestial; → latitude.

Angular distance to an object measured eastward along the → ecliptic from the → vernal equinox.

→ celestial; → longitude.

Derežnâ, → longitude; âsmâni→ celestial.

The branch of astronomy that deals with the calculation of motions of celestial bodies under the action of their mutual gravitational attractions.

→ celestial; → mechanics.

Mekânik, → mechanics; âsmâni, → celestial.

The great circle on the → celestial sphere, passing through the two → celestial poles and the observer's → zenith.

→ celestial; → meridian.