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

Same as → theoretician.

From theor-, from → theory + -ist a suffix of nouns, often corresponding to verbs ending in -ize or nouns ending in -ism.

→ theoretician.

A distance-like quantity derived from → gravitational lensing time delay. It is given by a combination of three angular diameter distances in a strong lens system: D_Δt = (1 + z_L)[D_A(EL)D_A(ES) / D_A(LS)], where z_L is the → redshift of the → gravitational lens, while D_A(EL), D_A(ES), and D_A(LS) are the angular diameter distances from the Earth to the lens, from the Earth to the source, and from the lens to the source, respectively. As each of the distance is proportional to the inverse of H₀, D_Δt is proportional to 1/H₀.

→ time; → delay; → distance.

An active semiconductor device with a small low-powered solid-state electronic device consisting of a semiconductor and three or more electrodes, used as an amplifier and rectifier and frequently incorporated into integrated circuit chips. Although much smaller in size than a vacuum tube, it performs similar functions without requiring current to heat a cathode.

From trans-, from → transfer + -istor, from → resistor; → resistance.

A Belgian facility devoted to the detection and characterization of → exoplanets and to the study of → comets (→ transiting planet) and other → small solar system bodies. It consists of two 60 cm robotic telescopes located at the → European Southern Observatory, → La Silla, in Chile and at Oukaïmden Observatory in Marroco.

→ transit; → planet; → planetesimal; → small; → telescope.

Describing a system or situation for which the → Lorentz factor, γ, is much larger than 1. See also → subrelativistic.

→ ultra- + → relativistic

A gas composed of ultrarelativistic particles.

→ ultrarelativistic; → gas.

The linear relation wherein all galaxies are moving away from one another, with velocities that are greater with increasing distance of the galaxy. Same as → Hubble's law.

→ velocity; → distance; → relation.

The disruption of the spherical shape of a wavefront due to atmospheric turbulence which makes the adjacent points in the wavefront out of phase.

→ wavefront; → distortion.

A whistling sound of descending pitch picked up by radio telescopes under certain circumstances. Whistlers are caused by radio waves from distant lightening flashes, which follow the lines of force of the Earth's magnetic field and are reflected back to Earth by the → ionosphere.

From M.E. whistler,; O.E. hwistlere, from hwistlian "whistle."

Sutzani "whistling," from "whistle," probably onomatopoeia + zani verbal noun from zadan "to make, to do," originally "to strike, beat; to do; to play an instrument" (Mid.Pers. zatan, žatan; O.Pers./Av. jan-, gan- "to strike, hit, smite, kill" (jantar- "smiter"); cf. Skt. han- "to strike, beat" (hantar- "smiter, killer"); Gk. theinein "to strike;" L. fendere "to strike, push;" Gmc. *gundjo "war, battle;" PIE *g^when- "to strike, kill").

1) The carpus or lower part of the forearm where it joins the hand.
2) The joint or articulation between the forearm and the hand (Dictionary.com).

M.E., O.E.; cognate with Ger. Rist "back of hand," O.Norse rist "instep;" akin to writhe.

Moc "wrist," related to mošt "fist;" Mid.Pers. mušt, must "fist;" Av. mušti- "fist;" cf. Skt. musti-, Pali mutthi-, L. manus (?).

An → X-ray source that does not display emission → outbursts, in contrast to → X-ray transients.

→ X-ray; → persistent.

The angular distance of a celestial body from the zenith. The zenith distance is 90° minus the body's altitude above the horizon (i.e. the complement of the altitude) and hence is also known as coaltitude.

→ zenith; → distance