An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1279
larzešenâsi (#)

Fr.: sismologie, séismologie   

The branch of geophysics that is concerned with the study of earthquakes and measurement of the mechanical properties of the Earth.

seismo-; → -logy.


Fr.: rarement   

Not → often; rarely.

M.E., from O.E. seldum, variant of seldan; cognate with Ger. selten, Goth. silda-, Dutch zelden.

Adverb from perz, → rare.

gozidan (#)

Fr.: sélectionner, choisir   

To choose from among several.

From L. selectus, p.p. of seligere "to choose out, gather apart," from se- "apart" + legere "to gather, select."

Gozidan "to select, choose;" Mid.Pers. vicitan, wizidan, wizin- "to choose, select, discriminate," related to cin-, cidan "to gather, collect;" Av. vicidāi- "to discern," viciθa- "separation, discernment;" from vi- "apart, away from" (O.Pers. viy- "apart, away;" cf. Skt. vi- "apart, asunder, away, out;" L. vitare "to avoid, turn aside") + kay- "to choose;" cf. Skt. ci- "to gather, heap up," cinoti "gathers."

selection rule
  رزن ِ گزینش   
razan-e gozineš

Fr.: règle de sélection   

Any of a set of rules specifying the relationships between the → quantum numbers that characterize the initial and final states of a quantum-mechanical system in a → discrete transition. Transitions that do not agree with the selection rules are called → forbidden and have considerably lower probability. There are several types of selection rules (→ rigorous selection rule, → LS coupling, etc.) for → electric dipole transition (→ permitted), → magnetic dipole (forbidden), electric → quadrupole (forbidden), etc.

Selection, verbal noun of → select; → rule.

selective absorption
  درشم ِ گزینشی   
daršam-e gozineši

Fr.: absorption sélective   

Absorption which varies with the wavelength of radiation incident upon an absorbing substance.

Selective, verbal noun of → select; → absorption.

selective scattering
  پراکنش ِ گزینشی   
parâkaneš-e gozineši

Fr.: diffusion sélective   

A type of scattering that occurs when certain → particles are more effective at scattering a particular → wavelength of light, as in → Rayleigh scattering.

selective; → scattering.

  ماه‌گرفت ِ افقی   
mâhgereft-e ofoqi

Fr.: selenelion   

Same as → horizontal eclipse.

From Gk. selene "Moon," related to sela "light, brightness, flame," + helion, → sun.

horizontal eclipse.

  ماه‌گرفت ِ افقی   
mâhgereft-e ofoqi

Fr.: selenelion   

Same as → horizontal eclipse.

From Fr. selenelion, contraction of → selenehelion.

horizontal eclipse.


Fr.: sélénocentrique   

Referring to or pertaining to the center of the Moon.

Formed on the model of → geocentric, from seleno- combining form of Gk. selene "moon" + -centric, from → center + → -ic.

Mâh-markazi, from mâh, → moon, + markazi, from markaz, → center, + -i, → -ic.

selenocentric gravitational constant
  پایای ِ گرانشی ماه‌مرکزی   
pâyâ-ye gerâneši-ye mâh-markazi

Fr.: constante gravitationnelle sélénocentrique   

A parameter representing the product of the → gravitational constant by the → lunar mass. It is 49.03 x 1011 m3 s-2.

selenocentric; → gravitational; → constant.

mâh-negâri (#)

Fr.: sélénographie   

Topographic description and charting of the surface of the Moon.

From seleno- combining form of Gk. selene "moon" + → -graphy.

Mâh-negâri, from mâh, → moon + negâri, → -graphy.

xod- (#)

Fr.: auto-   

A combining form of self with a range of related meanings.

From M.E., from O.E. self, seolf, sylf "one's own person, same;" cf. O.Fris. self, Du. zelf, O.H.G. selb, Ger. selbst.

Xod-, from xod; Mid.Pers. xwad "self; indeed;" Av. hva- "self, own."


Fr.: auto-absorption   

The decrease in the radiation from a material caused by the absorption of a part of the radiation by the material itself.

self-; → absorption.

  خود-آگاهی، خویشتن‌آگاهی   
xod-âgâhi, xištan-âgâhi

Fr.: connaissance de soi   

The → state or → condition of being aware of one's own → personality or → individuality.

self-; → awareness.


Fr.: auto-gravitant   

The characteristic of a system of masses, such as a star, kept together by mutual gravity.

self; → gravitate.


Fr.: auto-gravité   

The → gravitational attraction of a system of masses, such of a planet, that allows the system to be held together by their mutual gravity. Self-gravity between atoms allows a → star to hold together, despite tremendous temperature and pressure. Similarly, to be considered a → planet, a body must have enough mass so that its self-gravity pulls it into a near-spherical shape.

self-; → gravity.


Fr.: auto-inductance   

The inductance associated with an isolated electric circuit that is characteristic of the circuit's physical design.

self-; → inductance.


Fr.: auto-induction   

The generation of a voltage in a circuit due to self-inductance, the polarity of which tends to oppose the changing current in the circuit.

self-; → induction.

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.: auto-écrantage   

The phenomenon whereby the → photodissociation transitions of a molecule in interstellar clouds become → optically thick, so that the molecule in question is "shielded" by other molecules against dissociating stellar → far-ultraviolet (FUV) photons. In the case of → molecular hydrogen (H2), when the → column density exceeds 1014 cm-2, the UV absorption bands become optically thick, and H2 undergoes self-shielding. More specifically, all of the photons that could lead to UV photodissociation are absorbed by H2 in the outer layers of the cloud, hence protecting the H2 within the cloud. Self-shielding occurs in → diffuse interstellar clouds exposed to the interstellar → radiation field or in → molecular clouds in proximity to sources of UV photons. Dust can also absorb UV photons, further limiting the photodissociation, but it dominates only when the local UV radiation field is unusually intense relative to the density of the cloud.

self-; → shield; → -ing.

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