An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < bel lon > >>

Number of Results: 35 Search : long
long-period comet
  دمدار ِ درازدوره   
domdâr-e derâz dowré

Fr.: comète à longue période   

A comet with orbital period of more than 200 years. → short-period comet; → periodic comet.

long; → period; → comet.

long-period variable
  ورتنده‌ی ِ درازدوره   
vartande-ye derâz dowré

Fr.: variable à longue période   

A type of → variable star in which variations in brightness occur over long time-scales of months or years. The term generally refers to → Mira variable types.

long; → period; → variable.


Fr.: longitude   

The angular distance on the Earth's surface, measured east or west from the prime meridian at Greenwich to the meridian passing through a position, expressed in degrees (or hours), minutes, and seconds.

L. longitudo "length," from longus "long," cognate with Pers. derâz, as below, Gk. dolikhos "elongated;" O.H.G., Ger. lang, O.N. langr, M.Du. lanc, Goth. laggs "long;" PIE base *dlonghos- "long."

Derežnâ, from derež (Kurdi, Laki), variants darg "length; long, tall" (Zâzâ), darγ (Ossetic), derâz "long" + -nâ noun forming suffix from adjective, as in derâznâ, pah(n)nâ, farâxnâ, tangnâ, tiznâ. The first element from Mid.Pers. drâz "long;" O.Pers. darga- "long;" Av. darəga-, darəγa- "long," drājištəm "longest;" cf. Skt. dirghá- "long (in space and time);" PIE *dlonghos- "long," as above.

longitude of ascending node
  درژنای ِ گره ِ فرازشی   
derežnâ-ye gereh-e farâzeši

Fr.: longitude du nœud ascendant   

One of the → orbital elements used to specify the orbit of an object in space. It is the angle from the reference direction, called the origin of longitude, to the direction of the → ascending node, measured in the reference plane.

longitude; → ascending node.


Fr.: longitudinal   

Of or pertaining to longitude or length. Extending in the direction of the length.

Adj. of → longitude.

longitudinal magnetic field
  میدان ِ مغناطیسی ِ درژنایی   
meydân-e meqnâtisi-ye derežnâyi

Fr.: champ magnétique longitudinal   

1) A → magnetic field whose lines of force (→ line of force) run parallel to the long axis of the → magnet. Longitudinal magnetization of a component can be accomplished using the longitudinal field set up by a → coil or → solenoid. It can also be accomplished using permanent magnets or electromagnets.
2) In → stellar magnetic field observations, the magnetic field along the → line of sight.

longitudinal; → magnetic; → field.

longitudinal mass
  جرم ِ درژنایی   
jerm-e derežnâyi

Fr.: masse longitudinale   

In special relativity theory, the mass of a body when the acceleration is parallel or anti-parallel to velocity: ml = m0 / [1 - (v/c)2]3/2, where m0 is the → rest mass, v is the velocity, and c the → velocity of light. → transverse mass.

longitudinal; → mass.

longitudinal wave
  موج ِ درژنایی   
mowj-e derežnâyi

Fr.: onde longitudinale   

A wave vibrating along the direction of propagation, such as a → sound wave. → transverse wave.

longitudinal; → wave.

longitudinal Zeeman effect
  اُسکر ِ زیمن ِ درژنایی   
oskar-e Zeeman-e derežnâyi

Fr.: effet Zeeman longitudinal   

The → Zeeman effect when the emitting source is viewed in the direction of the magnetic field. In the normal longitudinal effect, each spectral line is split into two components with frequencies ν ± Δν. The line with the frequency ν - Δν shows left-hand → circular polarization and that with frequency ν + Δν shows right-hand circular polarization. → transverse Zeeman effect.

longitudinal; → Zeeman effect.


Fr.: oblong   

Elongated, usually from the square or circular form.

Late M.E. oblonge, from L. oblongus "rather long," from ob- a prefix meaning "toward, to, on, over, against" + longus, → long.

Derâzak, from derâz "long," → length + -ak suffix.

ring longitude
  درژنای ِ حلقه   
derežnâ-ye halqé

Fr.: longitude de l'anneau   

Of → Saturn, the angle measured with respect to the sub-observer point (a line connecting the observer to Saturn) in the direction of the orbital motion.

ring; → longitude.

solar longitude
  درژنای ِ خورشیدی   
derežnâ-ye xoršidi

Fr.: longitude du Soleil   

The ecliptic longitude of the Sun. It varies from 0° (at the vernal equinox) to 360° during the year. By Kepler's Second Law, the rate of change of the solar longitude is such that the Earth sweeps out equal areas on the ecliptic plane in equal times.

solar; → longitude.

supergalactic longitude
  درژنای ِ ابرکهکشانی   
derežnâ-ye abarkahkašâni

Fr.: longitude supergalactique   

supergalactic coordinate system.

supergalactic; → longitude.

very-long-baseline interferometry (VLBI)
  اندرزنش‌سنجی با پایه-خط ِ بسیار بزرگ   
andarzanešsanji bâ pâye-xatt-e besyâr bozorg

Fr.: interférométrie à très longue base   

A technique in radio interferometry in which the individual telescopes are not directly connected together, but instead make their observations separately with very accurate timings. The data are later sent to a central correlator to be combined. With this technique the individual telescopes can be arbitrarily far apart, and so the technique provides the highest resolution images in astronomy, typically down to a few milliarcseconds.

very; → large; → baseline; → interferometry.

western elongation
  درازش ِ باختری   
derâzeš-e bâxtari

Fr.: élongation ouest   

The position of a planet when it is visible in the eastern sky before dawn.

western; → elongation.

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