An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 46 Search : Ida
Achernar (Alpha Eridani)
  آخر ِ نهر، رودپایان   
Âxer-e nahr (#), Rudpâyân

Fr.: Achernar   

The brightest star in the constellation → Eridanus. A → subgiant of → spectral type B5; apparent visual magnitude 0.5, about 140 → light-years distant (other names: HR 472, HD 10144). Recent interferometric observations show it to have a flattened shape imposed by fast rotation.

Achernar, from Ar. Axir an-Nahr "end of the river," from axir "end" + nahr "river".

Âxer-e nahr, from Axir an-Nahr.
Rudpâyân "river's end," from rud "river," → Eridanus, + pâyân "end".

ezâdé (#)

Fr.: alidade   

1) In a → planispheric astrolabe, the small revolving rod fixed to the center of the goniometric scale plotted on the → front or → back of the instrument. Unlike the → rule, the alidade has little vanes with holes or slots at each end, called → pinnules, which are used as sights, through which the observer can aim at a particular object. An index, often consisting of the edge of the alidade itself, shows on the goniometric scales the angle between the line of sight of the targeted object and a predetermined axis, i.e. the vertical of the observation locality (online museo galileo, VirtualMuseum).
2) A rule having a sight at each end, used in surveying.
3) A topographic surveying and mapping instrument used for determining directions, consisting of a telescope and attached parts.

M.E. allidatha, alhidade, from L. alhidada, from Ar. al-'izâda (العضاده), from al- "the" + 'izâda "an armlet, a bracelet; a sickle-like piece of metal, used by camel drivers, to pull down tree branches to camels."

Ezâdé, from Ar. al-'izâda.


Fr.: absidial   

Relating to an → apsis.

apsis; → -al.

apsidal motion
  جنبش ِ هباکی   
jonbeš-e habâki

Fr.: mouvement apsidial   

Rotation of the → line of apsides in the plane of the orbit in the same direction as the → revolution of the → secondary body. The major axis of the Earth's orbit rotates by 11.6 arcseconds per year.

apsidal; → motion.

apsidal precession
  پیشایانِ هباکی   
pišâyân-e habâki

Fr.: précession absidiale   

advance of perihelion, → relativistic precession.

apsidal; → precession.


Fr.: évitable   

Able to be avoided or prevented.

avoid; → -ance.


Fr.: évitement   

The act of avoiding or keeping away from.

avoid; → -ance.

black hole candidate
  نامزد ِ سیه‌چال   
nâmzad-e siyah câl (#)

Fr.: candidat trou noir   

An object that seems likely to be a → black hole, but waits for more observational confirmations.

black; → hole; → candidate.

nâmzad (#)

Fr.: candidat   

1) An applicant or suitable person for a position.
2) An astronomical entity which is being considered for belonging to a special class of entities; e.g. → black hole candidate, → dark matter candidate, → supernova candidate.

From L. candidatus "clothed in white" (reference to the white togas worn by those seeking office), from candidus "shining white," from candere "to shine," cf. Skt. cand- "to shine," candra "bright; the Moon;" PIE base *kand- "to glow, to shine."

Nâmzad, literally "nominated," from nâm, → name, + zad, p.p. of zadan "to strike" (Mid.Pers. zatan, žatan, O.Pers./Av. jan-, gan- "to strike, hit, smite, kill," Skt. han- "to strike, beat," Gk. theinein "to strike," L. fendere "to strike, push," Gmc *gundjo "war, battle;" PIE *gwhen- "to strike, kill").

dark matter candidate
  نامزد ِ ماده‌ی ِ تاریک   
nâmzad-e mâdde-ye târik (#)

Fr.: candidat matière noire   

A hypothetical physical entity capable of accounting for the corresponding observed phenomena involving → dark matter. → Non-baryonic dark matter candidates include → WIMPs, → neutralinos, → axions, → gravitinos. Among → baryonic dark matter candidates can be noted ordinary and heavy → neutrinos, clouds of → neutral hydrogen gas, and compact objects.

dark; → matter; → candidate.

dwarf spheroidal galaxy (dSph)
  کهکشان ِ کره‌وار ِ کوتوله   
kahkašân-e korevâr-e kutulé (#)

Fr.: galaxie sphéroïdale naine   

A subtype of dwarf ellipticals (→ dwarf elliptical galaxy), which are companion to the → Milky Way and other similar galaxies. The first example of such objects was discovered by Harlow Shapley (1938) in the constellation → Sculptor. 22 such galaxies are known currently to orbit the Milky Way and at least 36 exist in the → Local Group of galaxies. Nearby → galaxy clusters such as the → Virgo, → Fornax, → Centaurus, and → Coma clusters contain hundreds to thousands of individual dSph galaxies. These galaxies have very low → surface brightnesses, as low as only 1% that of the → sky background. They are also among the smallest, least luminous galaxies known. Most of the radiation from dSph galaxies is emitted by stars in the optical portion of the → electromagnetic spectrum. The lack of strong → emission lines, → infrared, or → radio emission suggests that these galaxies are generally devoid of → interstellar medium. The velocities of stars within dSph galaxies are so high that them must be disrupting. However, the bulk of mass in these galaxies might be undetected. Dynamical models that include → dark matter do adequately explain the → velocity dispersion of the stars in all dSph systems. In the most extreme cases, only 1% of the mass of the galaxy is visible. Many of the Local Group dSph galaxies show evidence for → star formation more recent than 10 Gyr.

dwarf; → spheroidal; → galaxy.

Rud (#)

Fr.: Eridan   

The River. An extensive constellation in the southern hemisphere that takes windings between 1h20 and 5h 10m right ascension, 0° to 58° south declination. Despite its size, there are not many bright stars in this constellation. Notable are → Achernar and ε Eri, a dwarf star of magnitude 4.6 and type K2, which is just 10.7 light years away. Abbreviation: Eri; genitive: Eridani.

From Gk. Eridanos, a river god, a son of Oceanus and Tethys, and father of Zeuxippe. A purely mythical river which may have been named Eridanos ("Early Burnt") from the story of Phaethon, the boy who attempted to drive the chariot of the sun, and fell flaming into the waters of this mythical river.

Rud, → river.

  ۱) سپنت‌روز؛ ۲) آسودروز؛ ۳) آسودگان   
1) sepantruz; 2) âsudruz; 3) âsudgân

Fr.: 1); 2) férié; 3) vacances   

1) A day fixed by law or custom on which ordinary business is suspended in commemoration of some event or in honor of some person.
2) Any day of exemption from work.
3) (in plural form) A period of cessation from work or one of recreation; vacation.

O.E. haligdæg, from halig "holy," → heiligenschein, + dæg, → day.

1) Sepantruz, from sepant "holy," → heiligenschein, + ruz, → day.
2) Âsudruz, from âsud, âsudan "to rest, repose," from Mid.Pers. âsutan, Av. ā- + saē- (saii-) "to lie down, go to sleep;" + ruz, → day.
3) Âsudgân, from âsud, as before, + -gân suffix forming plurals.

Moon's apsidal precession
  پیشایان ِ هباکی ِ مانگ   
pišâyân-e habâki-ye mâng

Fr.: précession absidiale de la Lune   

The → rotation of the Moon's → orbit within the → orbital plane, whereby the axes of the ellipse change direction. The Moon's → major axis makes one complete revolution every 8.85 Earth years, or 3,232.6054 days, as it rotates slowly in the same direction as the Moon itself (direct, or → prograde motion). The Moon's apsidal precession is a → relativistic effect, and should not be confused with its → axial procession.

Moon; → apsidal; → precession.

  ا ُکسنده   
oksandé (#)

Fr.: oxydant   

The substance which supplies the → oxygen in an → oxidation → reaction. Same as → oxydizing agent agent and → oxidizer.

Agent noun from → oxidize.

  ا ُکسایش   
oksâyeš (#)

Fr.: oxydation   

The combination of → oxygen with a substance, or the removal of → hydrogen from it.

Verbal noun of → oxidize.

oxidation number
  شمار ِ اکسایش   
šomâr-e oksâyeš

Fr.: nombre d'oxydation   

The total number of electrons that an atom either gains or loses in order to form a chemical bond with another atom. In other words, the charge that atom would have if the compound was composed of ions. The oxidation number of an atom is zero in a neutral substance that contains atoms of only one element. Same as → oxidation state.

oxidation; → number.

oxidation state
  استات ِ اکسایش   
estât-e oksâyeš

Fr.: état d'oxydation   

Same as → oxidation number.

oxidation; → state.

poloidal magnetic field
  میدان ِ مغناتیسی ِ قطبی‌وار   
meydân-e meqnâtisi-ye qotbivâr

Fr.: champ magnétique poloïdal   

1) In → protoplanetary disk models, the magnetic field whose large-scale lines of force depart away from the → accretion disk, in the direction of the rotation axis.
2) In a → tokamak, the magnetic field produced by a current flowing in the → plasma vertically to the toroid plane. → toroidal magnetic field.

pole; → -oid; → magnetic field.

sinusi (#)

Fr.: sinusoïdal   

Having the characteristics of a sine function; same as → sine wave.

From sinus, → sine, + → -al.

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