An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 435 Search : ad
reading rate
  نرخ ِ خوانش   
nerx-e xâneš

Fr.: vitesse de lecture   

In computing and data processing, the number of words, characters, fields, etc. sensed by an input sensing device per unit of time.

Reading, verbal noun of read, from M.E. reden, O.E. rædan, redan "to counsel, read;" cf. Du. raden, Ger. raten "to advise, counsel, guess;" akin to Skt. rādh- "to succeed, accomplish;" Gk. arithmos "number amount;" L. ratio; Pers. rây, râ "because of, for the sake of;" → reason; → rate.

Nerx, → rate; xâneš verbal noun of xândan "to read; to sing; to call;" Mid.Pers. xwân- "to resound; to call;" Av. xvan- "to sound," Proto-Iranian *huan- "to call;" cf. Skt. svan-, sváranti "to sound, make a sound, sing;" L. sonus "sound," sonare "to sound;" O.E. swinn "music, song," PIE base *suen- "to sound" (Cheung 2007).

readout noise
  نوفه‌ی ِ خوانش   
nufe-ye xâneš

Fr.: bruit de lecture   

The noise added in the process of reading a detector such as a CCD.

reading rate; → noise.

recombination radiation
  تابش ِ بازمیازش   
tâbeš-e bâzmiyâzeš

Fr.: rayonnement de recombinaison   

Radiation produced when a free electron in a plasma is captured by an ionized atom.

recombination; → radiation.

reductio ad absurdum
  باز‌هازش به یاوه   
bâzhâzeš bé yâvé

Fr.: raisonnement par l'absurde   

Logic, Math.: A method of → reasoning in which one assumes some statement to be → true and from that → assumption proceeds to deduce a logical → absurdity and hence to a conclusion that the original assumption must have been → false.

L. reductio ad absurdum "reduction to absurdity," → reduction; → absurd.

  پسرو، پسرفت   
pasrow (#), pasraft (#)

Fr.: rétrograde   

Moving backward; having a backward motion or direction. → retrograde motion.

M.E., from L. retrogradus "going backward," from retrogradi "move backward," from retro- "backward" + gradi "to go, step."

Pasrow, pasraft, from pas- "back, behind," → back, + row, raft present and past stems of raftan "to go, walk;" (Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack").

retrograde motion
  جنبش ِ پسرو   
jonbeš-e pasrow

Fr.: mouvement rétrograde   

The orbital motion or rotation of a solar system body in a clockwise direction (East to West) when viewed from the north pole of the ecliptic. It is a motion opposed to the → direct motion of the great majority of solar system bodies.

retrograde; → motion.

retrograde object
  بر‌آخت ِ پسرو   
barâxt-e pasrow

Fr.: objet rétrograde   

An object which has a retrograde orbit around its primary.

retrograde; → object.

retrograde orbit
  مدار ِ پسرفت   
madâr-e pasraft

Fr.: orbite rétrograde   

An orbit with an inclination between 90° and 270° such as those of some comets and small asteroids orbiting the Sun.

retrograde; → orbit.

Richardson cascade
  پی‌شار ِ ریچاردسون   
peyšâr-e Richardson

Fr.: cascade de Richarson   

Same as → energy cascade

Named after L. F. Richardson (1922), Weather Prediction by Numerical Process (Cambridge Univ. Press); → cascade.

rotational broadening
  پهنش ِ چرخشی   
pahneš-e carxeši

Fr.: élargissement rotationnel   

The spectral line broadening caused by stellar rotation. Light from two rims of the star will be Doppler shifted in opposite directions, resulting in a line broadening effect. The line broadening depends on the inclination of the star's pole to the line of sight. The derived value is a function of ve. sini, where ve is the rotational velocity at the equator and i is the inclination, which is not always known. The fractional width (Δλ/λ) is of the order of 10-3 for B stars.

rotational; → broadening.

S Doradus star
  ستاره‌ی S ِ زرین ماهی   
setâre-ye S Zarrin-mâhi

Fr.: étoiles S Doradus   

A type of massive, → blue supergiant, → variable star, also known as a → Hubble-Sandage variable or a → Luminous Blue Variable (LBV). S Doradus stars are the most luminous stars in the Galaxy and are easily identified in other nearby galaxies. They are named after the prototype, S Doradus, in the → Large Magellanic Cloud.

Dorado; → star.

Sadalmelik (α Aquarii)
  سعد الملک   
sa'delmalek (#)

Fr.: Sadalmelik   

A supergiant star of type G2 Ib situated in the constellation → Aquarius. At a distance of 750 light-years, it has a luminosity 3000 times that of the Sun, and a diameter about 60 times the solar diameter. Variant designations: Sadalmelek; Sadlamulk; El Melik; Saad el Melik.

From Ar. Sa'd al-Malik (سعد الملک) "the lucky star of the ruler," for unknown reasons.

Sadr (γ Cygni)
Sadr (#)

Fr.: Sadr   

The star that lies at the center of → Cygnus's → Northern Cross. This F8 → supergiant is situated some 1,500 → light-years away and has an → apparent visual magnitude of 2.20.

From Ar. as-sadr (الصدر) "breast" (of the Cygnus).

Schwarzschild radius
  شعاع ِ شو‌آرتسشیلد   
šo'â'-e Schwarzschild

Fr.: rayon de Schwarzschild   

The critical radius at which a massive body becomes a → black hole, i.e., at which light is unable to escape to infinity: Rs = 2GM / c2, where G is the → gravitational constant, M is the mass, and c the → speed of light. The fomula can be approximated to Rs≅ 3 x (M/Msun), in km. Therefore, the Schwarzschild radius for Sun is about 3 km and for Earth about 1 cm.

Schwarzschild black hole; → radius.

self-shadowed disk
  گرده‌ی ِ خود-پرده، دیسک ِ ~   
gerde-ye xod-pardé, disk-e ~

Fr.: disque auto-écranté   

A model of → accretion disk around a → pre-main sequence star or a → protostar in which the outer parts of the disk are geometrically flat, in contrast to a → flared disk. Inward of a certain radius (0.5-1 AU from the star) the dust in the disk evaporates. Because the dust is the main source of opacity and the gas in the disk is usually optically thin, the irradiation burns a hole in the disk. Moreover, the inner rim puffs up, similarly to the case of flared disks. The difference lies in the outer parts. The inner rim casts its shadow over the disk all the way out. Since the disk thickness is almost constant, no photons can reach the surface of the disk and the outer parts of the disk remain shadowed by the inner rim and the midplane temperatures decrease accordingly. This model explains the observed → spectral energy distribution of some pre-main sequence stars, such as HD 101412. It also accounts for the observed weak → far infraredexcess, weak or no → PAH emission, and weak or no [O I] emission.

self-; → shadow; → disk.

Gerdé, → disk; xod-, → self-; pardé, → screen.


Fr.: ombre   

1) The comparative darkness caused by the interception or screening of rays of light from an object, place, or area.
2) A place or an area of comparative darkness, as one sheltered from the sun ( See also → shadow.

M.E. schade; O.E. scead "partial darkness; shelter," → shadow.

Sivân, from Kurd. sayvân "shadow, shade," variants si, sâ, sâyé, → shadow.

sâyé (#)

Fr.: ombre   

A dark patch formed by a body which obstructs rays of light.

M.E. sch(e)adew(e), schadow, shadw(e), O.E. sceadwe, sceaduwe, sceadu "shade, shadow, darkness;" cf. O.S. skado, M.Du. scade, Du. schaduw, O.H.G. scato, Ger. Schatten, Goth. skadus; from PIE base *skot- "dark, shade."

Sâyé "shadow," from Mid.Pers. sâyak "shadow;" Av. a-saya- "throwing no shadow;" Skt. chāya- "shadow;" Gk. skia "shade;" Rus. sijat' "to shine;" M.H.G. schinen, O.H.G. skinan, Ger. Schein "glow, shine;" PIE base *skai- "bright."

shadow bands
  نوارهای ِ سایه، باندهای ِ ~   
navârhâ-ye sâyé, bândhâ-ye ~

Fr.: ombres volantes   

Faint wavy lines of alternating light and dark that sometimes can be seen on flat, light-colored surfaces just before and just after a total solar eclipse. The phenomenon results from sunlight distortion by irregularities in the Earth's atmosphere.

shadow; → band.

shadow cone
  مخروط سایه   
maxrut-e sâyé

Fr.: cône d'ombre   

A cone-shaped shadow cast by Earth or the Moon pointing away from the Sun. The dark inner portion of the shadow cone is called the → umbra. The lighter outer portion of the shadow is called the → penumbra. Its extension is called the → antumbra.

shadow; → cone.

shoulder blade
  شانه، کتف   
šâné (#), ketf (#)

Fr.: omoplate   


shoulder; blade, M.E.; O.E. blæd "blade of grass;" cognate with Du. blad, Ger. Blatt.

Šâné, ketf, → scapula.

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