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

A member of a class of → low-mass X-ray binary systems containing low-magnetic field → neutron stars. They have soft spectra and no pulsations. An example is 4U 1705-44. See also → Z source.

→ atoll; the name derives from the fact that on X-ray → color-color diagrams these sources often resemble a band of points at constant hard X-ray color, with "islands" of points appearing on time-scales of weeks and months.

One of two light beams derived from the same source in → interference experiments. It is impossible to obtain interference from two separate sources because their → wavefronts do not have a constant → phase difference. In → Young's experiment, → Fresnel's biprism, → Fresnel's mirrors, and → Lloyd's mirror the two sources always have a point-to-point correspondence of phase, since they are both derived from the same source.

→ coherent; → source.

An object emitting intense energy in radio wavelength from a small, unresolved central region.

→ compact; → radio source.

A localized source on the celestial sphere that can be observationally separated at radio wavelengths from its background emission.

→ discrete; → radio; → source.

A → galaxy that emits radio energy from two regions located on opposite sides of the galaxy.

→ double; → lobe; → radio; → source.

In radio astronomy, a source whose angular extent could be measured, as distinguished from a point source.

→ extended; → source.

1) An astronomical object that emits → gamma rays.
2) A radioactive material that emits gamma rays in a form that can be used in medical imaging.

→ gamma ray; → source.

An electronic device designed to generate known amounts of radio noise in order to test and calibrate the receivers of radio telescopes.

→ noise; → source.

An observation when the telescope is pointed away from the source in order to measure the sky background contribution.

→ off-; → source; → observation.

An astronomical source emitting microwave radiation characteristic of the hydroxyl OH molecule, especially one showing a maser effect. OH sources are found in molecular clouds in interstellar medium and in the cool envelopes of evolved stars.

OH, chemical compound hydroxyl; → source.

In comparison with → off-source observation, an observation which is concerned with the source itself.

→ on-; → dource; → observation.

To obtain under contract with an outside supplier.

→ out; → source.

A source of radiation at a great distance from the observer; an ideal source of infinitesimal size.

→ point; → source.

A quasar with detectable radio emission.

→ quasi-; → stellar; → radio; → source.

A point or small portion of the sky giving stronger radio emission than the sky in its vicinity.

→ radio; → source.

An astronomical source in a field used as a reference for the detection of another object, astrometry, etc.

→ reference; → source.

1) A source of supply, support, or aid, especially one that can be readily drawn upon when needed.
2) (often plural) A source of economic wealth, especially of a country (mineral, land, labour, etc.) or business enterprise (capital, equipment, personnel, etc.) (Dictionary.com).

From Fr. ressourse, from O.Fr. resourdre "to rally, raise again," from L. resurgere "rise again," → re-, + → source.

Bâzxan, from bâz-, → re-, + xan, → source.

General: Any thing or place from which something comes, arises, or is obtained.
Physics: A point, line, or area in space from which the lines of force in a vector field originate.
Electricity: Any active component, battery, or generator that supplies energy.
Thermodynamics: Any body, device, or system that provides energy.

M.E., from O.Fr. sourse "a rising, beginning, fountainhead of a river or stream," from p.p. of sourdre "to rise, spring up," from L. surgere "to rise," → surge.

Xan "source," variant xân (Gilaki xoni, Tabari xoni,Laki kyani, Tâleši xâni, xoni,); Mid.Pers. xân, xânig "source, spring," Av. xâ-, xan- "source, fountain, spring," xayana- "belonging to a spring;" cf. Khotanese khâhâ- "spring, fountain;" Skt. khâ'- "spring, source."

For a radiating material, the ratio of emissivity to opacity.

→ source; → function.

An X-ray source that appears suddenly in the sky, strongly increases its intensity over a few days, and then declines with a lifetime of several months.

→ transient; → X-ray source.