An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 73 Search : field
field lens
  عدسی ِ میدان   
adasi-ye meydân

Fr.: lentille de champ   

A lens placed at or near the focal plane of a telescope to create an image of the primary mirror inside the instrument.

field; → lens.

field O star
  ستاره‌ی ِ Oی ِ میدان   
setâre-ye O-ye meydân

Fr.: étoile O de champ   

An → O-type star which is apparently not associated with a → star cluster. A significant fraction of → massive stars in the → Milky Way and other galaxies are located far from star clusters and → star-forming regions. It is known that some of these stars are → runaways, i.e. possess high → space velocities (determined through the → proper motion and/or → radial velocity measurements), and therefore most likely were formed in embedded clusters and then ejected into the field because of dynamical interactions or → binary-→ supernova explosions. However, there exists a group of field O stars whose runaway status is difficult to prove via direct proper motion measurements or whose low space velocities and/or young ages appear to be incompatible with their large separation from known star clusters. The existence of this group led some authors to believe that these stars can form → in situ. The question of whether or not O stars can form in isolation (→ isolated massive star formation) is of crucial importance for → star formation models (Gvaramadze et al., 2012, MNRAS, 424, 3037).

field; → O star.

field object
  بر‌آخت ِ میدان   
barâxt-e meydân

Fr.: objet de champ   

An astronomical object that is seen in the direction of a group but not physically belonging to the group. → field galaxy.

field; → object.

field of force
  میدان ِ نیرو   
meydân-e niru (#)

Fr.: champ de force   

The region of → space surrounding a body, such as a mass of → matter, a → charged particle, or a → magnet, within which it can exert a → force on another similar body not in contact with it.

field; → force.

field of view
  میدان ِ دید   
meydân-e did (#)

Fr.: champ de vue   

The entire angular expanse of the sky viewed by an optical instrument.

field; → view.

field rotation
  چرخش ِ میدان   
carxeš-e meydân

Fr.: rotation de champ   

The effect of the Earth's rotation on the position of the image formed on the → focal plane of a telescope during long exposures. In the case of → equatorial mounting, the image remains fixed, whereas it turns continuously with an → altazimuth mounting. In the latter case the image motion must be compensated by an appropriate mechanism, → field rotator.

field; → rotation.

field rotator
  چرخاننده‌ی ِ میدان   
carxânande-ye meydân

Fr.: rotateur de champ   

A device used on a telescope to correct for the → field rotation while tracking an object.

field; → rotator.

field star
  ستاره‌ی ِ میدان   
setâre-ye meydân

Fr.: étoile de champ   

A star that does not belong to a stellar cluster, but happens to be adjacent to it.

field; → star.

field stop
  دریچه‌ی ِ میدان   
darice-ye meydân

Fr.: diaphragme de champ   

A diaphragm located at an image plane of an optical system that determines the size and shape of the image. → aperture stop.

field; → stop.

field theory
  نگره‌ی ِ میدان   
negare-ye meydân

Fr.: théorie des champs   

1) A theory which uses the concept of → field to describe physical phenomena. It consists of two types: → classical field theory and → quantum field theory.
2) Math.: A branch of mathematics which studies the → fields.

field; → theory.

  میدان ِ تخت   

Fr.: champ plat   

Exposure of a diffuse and uniform source in order to calibrate the non-uniformity of an imaging detector such as a CCD.

flat; → field.

Meydân, → field; taxt, → flat.

force field
  میدان ِ نیرو   
meydân-e niru (#)

Fr.: champ de force   

Same as → field of force.

force; → field.

force-free magnetic field
  میدان ِ مغناتیسی ِ بی‌نیرو   
meydân-meqnâtisi-ye bi-niru

Fr.: champ magnétique sans force   

The condition in a plasma when the → Lorentz force is zero, that is when the electric current flows along the magnetic field. Force-free magnetic fields are encountered in astrophysical plasmas with negligible gas pressure. The solar corona is the best available example of such fields in action in a plasma.

force; → free; → magnetic; → field.

fossil magnetic field
  میدان ِ مغناتیسی ِ سنگواره، ~ ~ سنگواره‌ای   
meydân-e meqnâtisi-ye sangvâré, ~ ~ sangvâre-yi

Fr.: champ magnétique fossile   

In a physical system, the → magnetic field belonging to an earlier magnetic process or event. A fossil magnetic field may be a vanished one or exist in relic forms. As an example, the solar magnetic field, which was present during the formation of the Sun, has disappeared over the last 4.6 billions years.

fossil;→ magnetic; → field;

Frontier Fields
  میدانهای ِ مرزی   
Meydânhâ-ye Marzi

Fr.: Champs frontialers   

An observing project using the → Hubble Space Telescope (HST) and the → Spitzer Space Telescope to obtain deep images for cosmological studies. The Frontier Fields combines the power of HST and Spitzer with the natural gravitational telescopes of massive high-magnification clusters of galaxies to produce the deepest observations of clusters and their lensed galaxies ever obtained. Six clusters (Abell 2744, MACSJ0416.1-2403, MACSJ0717.5+3745, MACSJ1149.5+2223, Abell S1063, and Abell 370) were selected based on their lensing strength, sky darkness, Galactic extinction, parallel field suitability, accessibility to ground-based facilities, HST, Spitzer and JWST observability, and preexisting ancillary data. (Lotz et al., 2016, arxiv/1605.06567 and references therein).

frontier; → field.

frozen magnetic field line
  خط ِ میدان ِ مغناتیسی ِ یخ‌بسته، ~ ~ ~ رچیده   
xatt-e meydân-e meqnâtisi-ye yax basté, ~ ~ ~ rocidé

Fr.: ligne de champ magnétique gelée   

A → magnetic field line in a → fluid when the motion of the fluid carries the magnetic field along with it.

Frozen, p.p. of → freeze; → magnetic; → line.

geomagnetic field
  میدان ِ زمین‌مغناتیسی، ~ زمین‌مغناتی   
meydân-e zamin-meqnâtisi, ~ zamin-meqnâti

Fr.: champ géomagnétique   

The magnetic field that is generated within the Earth and extends out around the Earth. The intensity of the magnetic field at the Earth's surface is about 0.32 → gauss at the equator and 0.62 gauss at the north pole.

geomagnetic; → field.

gravitational field
  میدان ِ گرانشی   
meydân-e gerâneši (#)

Fr.: champ gravitationnel   

The region of space in which → gravitational attraction exists.

gravitational; → field.

gravitational-field theory
  نگره‌ی ِ میدان ِ گرانشی   
negare-ye meydân-e gerâneši (#)

Fr.: théorie de champ gravitationnel   

A theory that treats gravity as a field rather than a force acting at a distance.

gravitational; → field.

Habing field
  میدان ِ هابینگ   
meydân-e Habing

Fr.: champ de Habing   

A unit used to express the strength of average → far ultraviolet (FUV) intensity in the → interstellar radiation field. It is equal to 1.2 × 10-4 erg cm-2 s-1 sr-1 = 1.6 × 10-3 cm-2 s-1 = 108 photons cm-2 s-1.

Named after Harm Habing, a pioneer in this field (Habing, H. J., 1968, Bull. Astr. Netherlands 19, 421).

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