An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < -ab ab- abo abs abs acc acc aco act ad add adj aeo afo agr Alf alg Alk Aln Alp alt amb ana And ang ani ano ant ant Ap apo app app Ara arc Ari ars asp ast ast ast ath ato att aur aut axi > >>

Number of Results: 935
Ap star
  ستاره‌ی ِ Ap   
setâre-ye Ap

Fr.: étoile Ap   

A star of spectral type A in which lines of ionized metals and → rare-earth elements are abnormally enhanced. Such stars have unusually strong magnetic fields, thousands of times stronger than the Sun's typical surface field. Ap stars are generally slow rotators because of magnetic braking.

A for the spectral type, p for → peculiar; → star.

Ap/Bp star
  ستاره‌ی ِ Ap/Bp   
setâre-ye Ap/Bp

Fr.: étoile Ap/Bp   

A class of → intermediate-mass stars which possess anomalously strong → magnetic fields (about 100-10000 G). Ap/Bp stars typically show → overabundances of → iron peak elements, → rare earths, and → silicon, ranging up to ~2 dex above solar. These magnetic → chemically peculiar stars make up about 5% of the → main sequence A and B population (→ A star, → B star). Ap/Bp stars have predominantly → dipolar magnetic fields. The presence of strong, ordered magnetic fields in some main sequence A and B stars has been known for nearly one-half of a century (Babcock 1947). However the cause of the magnetic field is still a matter of debate. There are two competing theories: the contemporaneous → dynamo effect, and the → fossil magnetic field theory. Contemporaneous dynamo effect suggests that there is a dynamo effect currently working in the → convective core of the star. The fossil field theory assumes that the magnetic field is a remnant, produced by a dynamo effect operating at an earlier evolutionary phase, or swept up from the → interstellar medium during → star formation (Power et al., 2006, astro-ph/0612557).

A and B represent spectral types and p stands for → peculiar.

  اپاستار، اپاستاره   
apâstâr, apâsetâré

Fr.: apoastre   

The point at which a binary star is furthest from its companion.

Apastron, from Gk. ap-, → apo- + astron "star."

Apâstâr, apâsetâré, from apâ-, → apo-, + stâr, setâré, → star.

aperiodic damping
  میرایی ِ نادوره‌ای   
mirâyi-ye nâdowreyi

Fr.: amortissement apériodique   

A system in which the → damping is great enough to prevent oscillation.

Aperiodic, from → a- + periodic; + → damping.

dahâné (#)

Fr.: ouverture   

The diameter of the → primary mirror in a → reflecting telescope, the → objective lens in a → refracting telescope, the → dish of a → radio telescope, or the → entrance pupil of an instrument such as → spectrograph or → photometer.

From L. apertura, from apertus, p.p. of aperire "to open, uncover," from PIE *ap-wer-yo- from *ap- "off, away" + base *wer- "to cover".

Ddahâné "an opening," from dahân, → mouth.

aperture efficiency
  کار‌آیی ِ دهانه   
kârâyi-ye dahâné

Fr.: efficacité d'ouverture   

The ratio of the → effective aperture of a radio telescope to the true aperture.

aperture; → efficiency.

aperture photometry
  شیدسنجی ِ دهانه‌ای   
šidsanji-ye dahânéi

Fr.: photométrie d'ouverture   

Photometry using a diaphragm to isolate a small sky area, either directly with a focal-plane diaphragm, or with an image processing system.

aperture; → photometry.

aperture ratio
  وابر ِ دهانه   
vâbar-e dahâné

Fr.: rapport d'ouverture   

The ratio of the effective diameter of a lens or mirror to its focal length.

aperture; → ratio.

aperture stop
  دریچه‌ی ِ دهانه   
darice-ye dahâné

Fr.: diaphragme d'ouverture   

The diaphragm that limits the diameter of the axial light bundle allowed to pass through a lens.

aperture; → stop.

aperture synthesis
  هندایش ِ دهانه   
handâyeš-e dahâné

Fr.: synthèse d'ouverture   

The method of combining the signals received by several smaller telescopes distributed over a very large area or baseline to provide the high angular resolution of a much large telescope.

aperture; → synthesis.

cakâd (#)

Fr.: apex   

1) General: The highest point or level.
2) Mathematics: The highest point of a geometric figure or solid relative to some line or plane.
3) Astro.: Solar apex. The point on the celestial sphere toward which the Sun and the solar system are moving relative to the stars in our vicinity.

L. apex "summit, peak, tip," probably related to apere "to fasten, fix," hence "the tip of anything".

Cakâd "summit of a mountain; top, crown of the head, top of the forehead," from Mid.Pers. cakât "summit," cf. Skt. kakud-, kakuda- "peak, summit," L. cacumen "top, point," cumulus "heap."


Fr.: aphélie   

The point in the orbit of a planet, or other object in the solar system, which is furthest from the Sun.

Aphelion, from L. aphelium, from Gk. → apo- + helios "sun," cognate with L. sol, Skt. surya, Av. hvar-, Mod.Pers. xor, hur, O.H.G. sunna, Ger. Sonne, E. sun; PIE *sawel- "sun".

Apâhur, from Pers. prefix apâ, → apo-, + hur "sun."

aphelion distance
  اپست ِ اپاهوری   
apest-e apâhuri

Fr.: distance à l'aphélie   

The distance between the → Sun and an → object in orbit around it when they are at their farthest approach.

perihelion; → distance.

aplanatic lens
  عدسی ِ نابیراه   
adasi-ye nâbirah

Fr.: lentille aplanétique   

A lens designed so as to minimize both its → spherical aberration and → coma.

aplanatism; → lens.

aplanatic system
  راژمان ِ نابیراه   
râžmân-e nâbirah

Fr.: système aplanétique   

An → optical system that is able to produce an image essentially free from → spherical aberration and → coma. See also the → Abbe sine condition.

aplanatism; → system.


Fr.: aplanétisme   

Freedom from spherical aberration and coma.

Aplanatism, from aplanatic, from a- "negation prefix" + Gk. plane "wandering," from planasthai "to wander" + -tic adjective-forming suffix.

Nâbirahi, from nâ- "negation prefix" + birah "a devious path; a wanderer, who deviates, errs," + -i noun affix.


Fr.: apo-   

Prefix meaning "away from, off; out of; without," ap- before a vowel or h.

From Gk. apo "away from, from;" cf. Av. apâ "away from, from."

Persian apâ- from Av. and O.Pers. apâ "away from, from". Compare with Skt. apa "away, off," L. ab- "from, away," Hittite appa, Gothic af-, Ger. ab-, E. of, off; PIE *apo- "off, away."


Fr.: apoapse   

The point in an orbit where the moving body lies furthest from the celestial body around which it turns.

Apoapsis, from → apo- + → apsis.

Apâhabâk, from apâ-, → apo-, + habâk, → apsis.


Fr.: apocentre   

The point on an elliptic orbit at the greatest distance from the principal focus or center of attraction.

Apocenter, from → apo- + → center.

Apâmarkaz, apâkayân, from apâ-, → apo-, + markaz or kayân, → center.

  عدسی ِ اپافام   
adasi-ye apâfâm

Fr.: apochromatique   

Same as → apochromatic lens.

<< < -ab ab- abo abs abs acc acc aco act ad add adj aeo afo agr Alf alg Alk Aln Alp alt amb ana And ang ani ano ant ant Ap apo app app Ara arc Ari ars asp ast ast ast ath ato att aur aut axi > >>