An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 584
thick disk
  گرده‌ی ِ ستبر، دیسک ِ ~   
gerde-ye setabr, disk-e ~

Fr.: disque épais   

A disk component of a → spiral galaxy that lies above the → thin disk and mainly consists of stars. The thick disk of our → Galaxy makes up about 10-50% of the stellar mass of the → Milky Way and has a scale height of ~ 1,000-3,000 → light-years. Thick disk stars are, on average, moving faster in a vertical direction with respect to the → galactic plane than thin disk stars. In contrast to thin disk, the stars within the thick disk are almost all older than 10 billion years and typically have a smaller → metallicity than the average values for the thin disk stars. These facts suggest that the formation scenarios for the thin and thick disks were different. In particular, it is thought that the thick disk is much older than the thin disk.

thick; → disk;

thick lens
  عدسی ِ ستبر   
adasi-ye setabr

Fr.: lentille épaisse   

A lens whose thickness is not small compared with its focal length. The thick lens may include several components, which may or may not be in contact. → thin lens.

thick; → lens.

setabrâ (#)

Fr.: épaisseur   

The state or quality of being thick. → optical thickness.

M.E. thiknesse, O.E. thicnes, from → thick + -nes(s) suffix of action, quality or state, cf. M.Du. -nisse, O.H.G. -nissa, Ger. -nis, Goth. -inassus.

Setabrâ, from setabrthick + a suffix forming nouns from adjectives.

rân (#)

Fr.: cuisse   

The part of the human → leg between the → hip and the → knee.

M.E. thi, thigh(e), the(h), O.E. thioh, theoh; cognate with Du. dij, O.H.G. dioh, O.Norse thjo.

Rân, from Mid.Pers. rân "thigh;" Av. rāna- "the outer part of the thigh."

nâzok (#)

Fr.: mince   

Having relatively little extent from one surface or side to the opposite; not thick. → optically thin; → superthin galaxy.

M.E. thyn(ne), O.E. thynne, from P.Gmc. *thunnuz, *thunw- (cf. W.Fris. ten, M.L.G. dunne, Du. dun, O.H.G. dunni, Ger. dünn), from PIE *tnus-, *tnwi-, from base *ten- "stretch;" cf. Pers. tonok "thin, slender," → attenuate.

Nâzok, from Mid.Pers. nâzuk, nâzik "tender, gentle."

thin disk
  گرده‌ی ِ نازک، دیسک ِ ~   
gerder-ye nâzok, disk-e ~

Fr.: disque mince   

A disk component of a → spiral galaxy containing → stars, → gas, and → dust which are confined to the galaxy's → plane of rotation. In contrast to → thick disks, thin disks contain the bulk of the → baryonic matter in spiral galaxies. For example, on the order of 60-90% of the baryonic matter in the → Milky Way is located in the thin disk. The scale height of the thin disk in the Milky Way is about 400 → light-years, whereas its scale length is about 10,000 light-years. Moreover, the outer regions of thin disks appear to be bent by the → warp phenomenon. The thin disks of spiral galaxies are active sites of → star formation, especially in the spiral arms. For this reason, stars in the thin disk tend to be relatively young. Thin disk stars also tend to be → metal-rich compared with thick disk and → halo stars, and typically have a → metallicity similar to that of the Sun.

thin; → disk;

thin lens
  عدسی ِ نازک   
adasi-ye nâzok (#)

Fr.: lentille mince   

A lens whose thickness is considered small in comparison with the distances generally associated with its optical properties. Such distances are, for example, radii of curvature of the two spherical surfaces, primary and secondary focal lengths, and object and image distances. → thick lens.

thin; → lens.

ciz (#)

Fr.: chose   

1) A material object without life or consciousness; an inanimate object.
2) Some entity, object, or creature that is not or cannot be specifically designated or precisely described.
3) Anything that is or may become an object of thought (

M.E. thing; O.E. þing "meeting, assembly, discussion;" cf. O.Norse þing "assembly, meeting, council;" O.Frisian thing "assembly, action, matter, thing;" O.Saxon thing; O.Du. dinc "law suit, matter, thing;" M.Du. ding; Du. ding; O.Ger. ding, dinc "assembly;" M.H.G. dinc "assembly;" Ger. ding "matter, affairs, thing." Hence, the word originally meant "assembly, meeting," then came to mean a specific issue discussed at such an assembly, and finally came to indicate "an object."

Ciz, from Mid.Pers. ciš, tis "thing, affair;" O.Pers. cišciy "anything."


Fr.: penser, réfléchir   

To employ one's mind rationally and objectively in evaluating or dealing with a given situation.

M.E. thinken, variant of thenken, O.E. thencan; P.Gmc. *thankjan (cf. O.Fris. thinka, O.S. thenkian, O.H.G. denchen, Ger. denken, Goth. thagkjan).

Andišidan, infinitive from andiš-; Mid.Pers. handeš-, handešidan "to think, consider, reflect," ultimately from Proto-Iranian *ham-dis-, from *ham- "together, with, same," → syn- + *dis- "form, appearance," cf. Av. daēs- "to show," daēsa- "sign, omen;" Mod.Pers. dis, disé "form, appearance," variants -diz, -diš; Mid.Pers. dêsag "form, appearance," dêsidan "to form, build;" Sogd. andiš "to seem," andêš "to show," andêšik "appearing;" cf. Skt. deś- "to show, point out;" PIE *deik- "to show" (cf. Gk. deiknumi "to show," dike "manner, custom;" L. dicere "to utter, say;" O.H.G. zeigon, Ger. zeigen "to show;" O.E. teon "to accuse," tæcan "to teach").

sevom (#)

Fr.: troisième   

Next after the second; the ordinal number for three. → Newton's third law of motion; → third contact; → third dredge-up; → third law of thermodynamics.

M.E. thirde, O.E. (north) thirda, variant of ridda, from P.Gmc. *thridjas (cf. O.Fris. thredda, O.S. thriddio, M.L.G. drudde, Du. derde, O.H.G. dritto, Ger. dritte, Goth. thridja).

Sevom, ordinal number for , → three.

third contact
  پرماس ِ سوم   
parmâs-e sevom

Fr.: troisième contact   

The end of the total phase of a solar eclipse marked by the trailing edge of the Moon first revealing the Sun.

third; → contact.

third dredge-up
  برونکشید ِ سوم   
borunkešid-e sevom

Fr.: troisième dragage   

A → dredge-up process that occurs in the stellar interior during He shell burning, as in → asymptotic giant branch (AGB) stars. These stars consist of a degenerate carbon-oxygen core, surrounded by a helium-rich region, above which lies a hydrogen-rich convective envelope. Following thermal pulses of the helium-burning shell, the convective envelope moves inward in mass, penetrating the hydrogen-exhausted regions. This is known as third dredge-up. As convection moves inward, nuclear processed materials are carried to the surface.

third; → dredge-up.

third law of thermodynamics
  قانون ِ سوم ِ گرماتوانیک   
qânun-e sevom-e garmâtavânik

Fr.: troisième loi de la thermodynamique   

The → entropy of an idealized state of maximum order is zero at the temperature of → absolute zero. Another version of this law: As a system approaches absolute zero, all processes cease and the entropy of the system approaches a minimum value.

third; → law; → thermodynamics.

third quarter
  چارک ِ سوم   
cârak-e sevom

Fr.: troisième quartier   

The phase of the Moon when half the visible disk of the waning Moon is illuminated. This quarter occurs when the celestial longitude of the Moon is 270° greater than the Sun's.

third; → quarter.

si (#)

Fr.: trente   

A cardinal number, 10 times 3.

M.E. thritty, O.E. thritig, from thri, threo "three" + -tig "group of ten, -ty."

Si, from Mid.Pers. sih; O.Pers. *ciθas nominative singular of *ciθant-; Av. θrisant- "thirty;" cf. Skt. trimśát- "thirty."

Tholen classification
  رده‌بندی ِ تولن   
radebandi-ye Tholen

Fr.: classification de Tholen   

A fundamental system for the classification of → asteroids based on → albedo and → spectral characteristics. The Tholen scheme includes 14 types with the majority of asteroids falling into one of three broad categories, and several smaller types. → C-type asteroid, → M-type asteroid, → S-type asteroid.

David J. Tholen (1984) Ph.D. thesis, University of Arizona; → classification.


Fr.: Thomson   

The British physicist Sir Joseph John Thomson (1856-1940), discoverer of the electron (1897), Nobel Prize in Physics (1906). → Thomson atom, → Thomson cross section, → Thomson effect, → Thomson scattering, → Joule-Thomson effect.

Thomson atom
  اتم ِ تامسون   
atom-e Thomson (#)

Fr.: atome de Thomson   

The earliest theoretical description of the inner structure of atoms whereby an atom consists of a sphere of positive electricity of uniform density, throughout which is distributed an equal and opposite charge in the form of electrons. The diameter of the sphere was supposed to be of the order of 10-8 cm, the magnitude found for the size of the atom. → Rutherford atom.

Thomson; → atom.

Thomson cross section
  سکنج‌گاه ِ تامسون   
sekanjgâh-e Thomson

Fr.: section efficace de Thomson   

The → cross section involved the → Thomson scattering of electromagnetic waves by a free electron. It is defined by: σT = 8πre2/3, where re is the classical → electron radius. Its value is 0.665 245 x 10-28 m2.

Thomson; → cross; → section.

Thomson effect
  اسکر ِ تامسون   
oskar-e Thomson

Fr.: effet de Thomson   

The absorption or emission of heat when current is passed through a single conductor whose ends are kept at different temperatures. If current is passed from hotter end to colder end of a copper wire, then heat is evolved along the length of the wire. When current is passed from colder end to the hotter end, then heat is absorbed.

Thomson; → effect.

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