An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 611

Fr.: isoplanatique   

The quality of an imaging system which is characterized by → isoplanatism.

From → iso- "equal, uniform" + Gk. plane "wandering," from planasthai "to wander" + -tic adjective-forming suffix, → -ic.

Izobirâh, from izo-, → iso-, + birâh "a devious path; a wanderer, who deviates, errs."

isoplanatic angle
  زاویه‌ی ِ ایزوبیراه   
zâviye-ye izobirâh

Fr.: angle isoplanatique   

The angle in which the → point spread function of the atmosphere/telescope system is space invariant. Because of the presence of → turbulence in high layers of the atmosphere, this angle is extremely small, often only a few seconds of arc at visible wavelengths. See also → aplanatism.

isoplanatic; → angle.

isoplanatic patch
  پچ ِ ایزوبیراه، تکه‌ی ِ ~   
pac-e izobirâh, teke-ye ~

Fr.: tache isoplanatique   

The spatial region where the variation of the → point spread function of an imaging system is considered negligible.

isoplanatic; → patch.

  ایزوبیراهی، ایزوبیراهمندی   
izobirâhi, izobirâhmandi

Fr.: isoplanatisme   

In an imaging system, the unvarying of the → point spread function over an extended field of view.

From isoplanat(ic), → isoplanatic, + → -ism.


Fr.: isoplanicité   

The condition in which the wavefronts arriving from different parts of a region of sky undergo almost identical phase perturbations. See also → isoplanatic patch.

isoplanatic; → patch.

  ایزوچند، هم‌چند   
izocand, hamcand

Fr.: isoplèthe   

A line on a map connecting points of equal value. For example the contour lines joining points of equal altitude on a topographic map. Some other examples of isopleths are: → isobar, → isoneph, and → isohel.

From Gk. isoplethes, from → iso- + pleth(os) "great number, multitude;" cognate with Pers. por, → full, + -es adj. suffix.

Izocand, from izo-, → iso-, + cand replacing candi (after prefix) "quantity," from Mid.Pers. candih "amount, quantity," from cand "how many, how much; so many, much;" O.Pers. yāvā "as long as;" Av. yauuant- [adj.] "how great?, how much?, how many?," yauuat [adv.] "as much as, as far as;" cf. Skt. yāvant- "how big, how much;" Gk. heos "as long as, until."

isosceles triangle
  سه‌بر ِ دو-پهلو-برابر   
sebar-e do-pahlu-barâbar (#)

Fr.: triangle équilatéral   

A triangle having two sides equal.

From L.L. isosceles, from Gk. isoskeles "with equal legs; that can be divided into two equal parts," from isos "equal, identical," → iso-, + skelos "leg."

Sebar, → triangle, do-pahlu-baraabar, from do, → two, pahlu, → side, barâbar, → equal.

izospin (#)

Fr.: isospin   

A quantum number based on the assumption that the nucleon (proton and neutron) is a single entity having two states, like → spin. It is conserved by the strong interaction. Same as isotopic spin, isobaric spin.

From → iso- + → spin


Fr.: isotherme   

Meteo.: A line on a map or graph joining points of equal temperature.

Isotherm, back formation from → isothermal.

Izodamâ, from → iso- + damâ, → temperature.


Fr.: isotherme   

1) Relating to or having a constant temperature.
2) Pertaining to an → isotherm.

Isothermal, from → iso- + therm, from Gk. therme "heat" thermos "warm;" cognate with Pers. garm "warm" (garmâ "heat, warmth," from Mid.Pers. garmâg; O.Pers./Av. garəma- "hot, warm;" cf. Skt. gharmah "heat;" L. formus "warm," fornax "oven;" P.Gmc. *warmaz; O.E. wearm; E. warm; O.H.G., Ger. warm; PIE *ghworm-/*ghwerm- "warm") + → -al; → process.

Izodamâ, from → iso- + damâ, → temperature.

isothermal process
  فراروند ِ ایزودما   
farâravand-e izodamâ

Fr.: processus isotherme   

A → thermodynamic process that takes place at → constant  → temperature. For the temperature of a system to remain strictly constant, the changes in other coordinates (pressure and volume) must be carried out slowly, and → heat must enter or leave the system to maintain a constant temperature. → polytropic process. Astrophysical examples include the → collapse of a → protostar down the → Hayashi track, and the collapse of a star at the end of its life to become a → white dwarf.

isothermal; → process.

isothermal wind
  باد ِ ایزودما   
bâd-e izodamâ

Fr.: vent isotherme   

A → stellar wind in which the gas is subject to only two forces: the inward directed gravity and the outward directed gradient of the gas pressure.

isothermal; → wind.

izoton (#)

Fr.: isotone   

One of several nuclides having the same number of neutrons in their nuclei but differing in the number of protons.

Isotone, from → iso- + tone, from Gk tonos "strain, tone, mode," literally, "a stretching," akin to teinein "to stretch," cognate with Pers. tanidan "to spin, twist, weave" (Mid.Pers. tanitan; Av. tan- "to stretch, extend;" cf. Skt. tan- to spin, stretch;" tanoti "stretches," tantram "loom;" Gk. teinein "to stretch, pull tight;" L. tendere "to stretch; PIE base *ten- "to stretch;" Pers. târ "string," tân "thread," tur "fishing net, net, snare," and tâl "thread" (Borujerdi dialect) belong to this family; variants tanta "cobweb," tanadu, tafen, kartané, kârtané, kâtené, Pashtu tanistah "cobweb;" cf. Skt. tantu- "cobweb, thread, string").

  ایزوتوپ، همجا   
izotop (#), hamjâ (#)

Fr.: isotope   

One of two or more atoms having the same number of protons in its nucleus, but a different number of neutrons and, therefore, a different mass.

Isotope, from → iso- + -tope, from Gk. topos "place."

Izotop, loan from Fr., as above. hamjâ, from ham- "together" → com- + "place" (from Mid.Pers. giyag "place;" O.Pers. ā-vahana- "place, village;" Av. vah- "to dwell, stay," vanhaiti "he dwells, stays;" Skt. vásati "he dwells;" Gk. aesa (nukta) "to pass (the night);" Ossetic wat "room; bed; place;" Tokharian B wäs- "to stay, wait;" PIE base ues- "to stay, live, spend the night").

isotope fractionation
  برخانش ِ ایزوتوپی   
barxâneš-e izotopi

Fr.: fractionnement isotopique   

A slight difference between the → abundances of → isotopes of the same → chemical element owing to → physical or → chemical  → processes. It results in the → enrichment or → depletion of an isotope. Same as → isotopic fractionation.

isotope; → fractionation

isotope shift
  کیب ِ ایزوتوپی   
kib-e izotopi

Fr.: décalage isotopique   

A displacement in the spectral lines due to the different isotopes of an element.

isotope; → shift.

izotopi (#)

Fr.: isotopique   

Of or relating to an → isotope.

isotope; → -ic.

isotopic fractionation
  برخانش ِ ایزوتوپی   
barxâneš-e izotopi

Fr.: fractionnement isotopique   

Same as → isotope fractionation.

isotopic; → fractionation

isotopic number
  عدد ِ ایزوتوپی   
adad-e izotopi

Fr.: nombre isotopique   

The difference between the number of neutrons in an isotope and the number of protons. Neutron excess.

isotopic; → number.

isotopic ratio
  وابر ِ ایزوتوپی   
vâbar-e izotopi

Fr.: rapport isotopique   

The relative abundances of two isotopes of a given chemical element, such as D/H (deuterium/hydrogen), (carbon) 12C/13C, and (uranium) 235U/238U.

isotopic; → ratio.

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