An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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source function
  کریای ِ خن   
karyâ-ye xan

Fr.: fonction source   

For a radiating material, the ratio of emissivity to opacity.

source; → function.

space mission
  گسیلان ِ فضایی   
gosilân-e fazâyi

Fr.: mission spatiale   

A manned or unmanned space flight outside the Earth's atmosphere.

space; mission, from L. missionem (nominative missio) "act of sending," from mittere "to send," of unknown origin.

Gosilân, from gosil, variant gosi "sending away, dismission;" Mid.Pers. wisé "to despatch" (Parthian Mid.Pers. wsys- "to despatch;" Buddhist Mid.Pers. wsydy "to despatch;" Sogdian 'ns'yd- "to exhort"), from Proto-Iranian *vi-sid- "to despatch, send off," from prefix vi- "apart, away, out," + *sid- "to call" + -ân nuance suffix; fazâyi adj. of fazâ, → space.

space motion
  جنبش ِ فضایی   
jonbeš-e fazâyi

Fr.: mouvement spatial   

The velocity and direction of motion of a star or celestial object with respect to the Local Standard of Rest. Same as → peculiar velocity.

space; → motion.

Space Situational Awareness (SSA)
  آگاهی از سیتش ِ فضایی   
âgâhi az siteš-e fazâyi

Fr.: surveillance de l'environnement spatial   

A program aimed at monitoring the near-Earth environment for recognizing and preventing space hazards by means of radar and optical observations from either space or the ground. The objective of the → European Space Agency initiative is to support the European independent utilization of, and access to, space for research or services, through the provision of timely and quality data, information, services and knowledge regarding the space environment, the threats and the sustainable exploitation of the outer space surrounding our planet Earth. The SSA Program was authorized at the November 2008 Ministerial Council and formally launched on 1 January 2009. The mandate was extended at the 2012 and 2016 Ministerial Councils, and the program is funded through to 2020. The program comprises three segments: 1) Space Surveillance and Tracking (SST), which is the monitoring and tracking of every object orbiting the Earth, such as satellites, space stations and debris. The objective is the prediction and warning of collisions and re-entry events. 2) → Space Weather (SWE), which aims at detection and forecasting of space weather and its effects through monitoring of the Sun, solar wind, magnetosphere, radiation belts, ionosphere and disturbances in the geomagnetic field. 3) → Near-Earth Objects (NEOs), which provides warning services against potential asteroid impact risks, including discovery, identification, orbit prediction and civil alert capabilities.

space; → situation; → -al; → awareness.

space station
  ایستگاه ِ فضایی   
istgâh-e fazâyi

Fr.: station spatiale   

A large satellite equipped to support a human crew and designed to remain in orbit around Earth for an extended period and be used for a variety of purposes (conducting research, repairing satellites, performing other space-related activities).

space; → station.


Fr.: spallation   

A nuclear reaction in which a high energy particle that collides with a nucleus causes the target to eject several particles, thus changing both its mass number and its atomic number.

From → spall + -ation.

Verbal noun from terišidan, → spall.

spatial resolution
  واگشود ِ فضایی   
vâgošud-e fazâyi

Fr.: résolution spatiale   

The smallest detail that can be seen in an image. Same as → angular resolution.

spatial; → resolution.

specific star formation rate (sSFR)
  نرخ ِ آبیزه‌ی ِ دیسش ِ ستارگان   
nerx-e âbize-ye diseš-e setâregân

Fr.: taux de formation d'étoiles spécifique   

Star formation rate per unit → mass. More specifically, the → star formation rate in a galaxy divided by the → stellar mass of the galaxy. Observations of galaxies over a wide range of → redshifts suggest that the slope of the SFR-M* relation is about unity, which implies that their sSFR does not depend strongly on stellar mass. Specific star formation rates increase out to z ~ 2 and are constant, or perhaps slowly increasing, from z = 2 out to z = 6, though with a large scatter, sSFR ~ 2-10 Gyr-1 (Lehnert et al., 2015, A&A 577, A112, and references therein).

specific; → star; → formation; → rate.


Fr.: précision, spécification   

1) The act of specifying.
2) A particular item, aspect, calculation, etc., in such a description.
3) Something specified, as in a bill of particulars; a specified particular, item, or article (

Verbal noun of → specify.

spectral classification
  رده‌بندی ِ بینابی   
radebandi-ye binâbi (#)

Fr.: classification spectrale   

A system that assigns a → spectral type to a star according to characteristics of its spectrum. The earliest attempt to divide stars on the basis of their spectra was the → Secchi classification in the 1860s. This scheme paved the way for the → Harvard classification that led to the current → Morgan-Keenan classification of spectral types. In the Harvard system stars were originally thought to follow an evolutionary sequence from the "early" O and B types to the "late" K and M types. Although this is now known to be wrong, the terms → early-type star and → late-type star are still in use. In the Morgan-Keenan system stars are classified as type O, B, A, F, G, K, or M in order of decreasing → effective temperature, and each type further subdivided into subclasses from 0 (hottest, except for → O-type stars) to 9 (coolest). They are also accompanied by a → luminosity class. In the late 1990s, spectral types L and T were added to the sequence to accommodate the coolest stars and → brown dwarfs (with class Y reserved for the coolest brown dwarfs of all, as yet unobserved).

spectral; → classification.

spectral dispersion
  پاشش ِ بینابی   
pâšeš-e binâbi

Fr.: dispersion spectrale   


spectral; → dispersion.

spectral energy distribution (SED)
  واباژش ِ کاروژ ِ بینابی   
vâbâžeš-e kâruž-e binâbi

Fr.: distribution de l'énergie spectrale   

A plot showing the energy emitted by a source as a function of the radiation wavelength or frequency. It is used in many branches of astronomy to characterize astronomical sources, in particular mainly in → near infrared and → middle infrared to study → protostars or → young stellar objects. The SED of these objects is divided in four classes.
Class 0 in which the SED represents a very embedded protostar, where the mass of the central core is small in comparison to the mass of the → accreting envelope. The SED is characterized by the → blackbody radiation of the envelope and peaks at → submillimeter wavelengths.
Class I objects possess a SED that peaks in the → far infrared and is characterized by a weak contribution of the blackbody of the central protostar (detected in near infrared) and the emission of a thick disk and dense envelope. These objects have less mass in the envelope and more massive central cores with respect to Class 0.
Class II objects are the → classical T Tauri stars with a SED due to the emission of a thin disk and the central star. They have accumulated most of their final mass and have dispersed almost completely their circumstellar envelope.
Finally, Class III objects have pure photospheric spectra. Their SED is peaked in the optical and is well approximated by a blackbody emission with a faint → infrared excess due to the presence of a residual optically thin disk that may be the origin of → planetesimals.
This classification scheme can be made more quantitative by defining a → spectral index.

spectral; → energy; → distribution.

spectral region
  ناحیه‌ی ِ بینابی   
nâhiye-ye binâbi

Fr.: région spectrale   

An extent of wavelengths into which the electromagnetic spectrum is divided; e.g. infrared or ultraviolet region.

spectral; → region.

spectral resolution
  واگشود ِ بیناب، ~ بینابی   
vâgošud-e binâb, ~ binâbi

Fr.: résolution spectrale   

The capacity of a spectrograph to separate two adjacent spectral lines. The theoretical spectral resolution depends on the grating dispersion, grating position, pixel size, collimator and camera focal length, and the entrance slit-width.

spectral; → resolution.

spectral response
  پاسخ ِ بینابی   
pâsox-e binâbi

Fr.: réponse spectrale   

Domain of the electromagnetic spectrum over which a detector is sensitive. Same as spectral sensitivity.

spectral; → response.

Spectro-Polarimetric High-contrast Exoplanet (SPHERE)

Fr.: Spectro-Polarimetric High-contrast Exoplanet (SPHERE)   

The → extreme adaptive optics system and → coronagraphic facility at the → European Southern Observatory (ESO) → Very Large Telescope (VLT) (UT3) available from May 2014. Its primary science goal is imaging, low-resolution spectroscopic, and polarimetric characterization of → exoplanetary system at → visible and → near-infrared wavelengths (0.5-2.32 μm). SPHERE is capable of obtaining → diffraction-limited images at 0''.02 to 0''.08 resolution depending on the wavelength. Its → spectral resolution is 30 to 350, depending on the mode.

spectro-; → polarimetric; → high; → contrast; → exoplanet.

specular reflection
  بازتاب ِ آینه‌وار   
bâztâb-e âyenevâr (#)

Fr.: réflexion spéculaire   

The reflection of light waves in which the reflected waves travel in a definite direction, and the directions of the incident and reflected waves make equal angles with a line perpendicular to the reflecting surface. Same as → regular reflection; opposite of → diffuse reflection.

From L. specularis, from speculum "mirror;" → reflection.

Bâztâb, → reflection; âyenevâr "mirror-like," from âyené, → mirror + -vâr similarity suffix.


Fr.: spéculation   

The act or an instance of speculating.

Verbal noun of → speculate.

spherical aberration
  بیراهش ِ کُره‌ای   
birâheš-e koreyi

Fr.: aberration sphérique, ~ de sphéricité   

An aberration of a spherical lens or spherical mirror in which light rays converge not to a single point but to a series of points with different distances from the lens or mirror. Spherical aberration is corrected by using parabolic reflecting and refracting surface.

spherical; → aberration.

spherical astronomy
  اخترشناسی ِ کُره‌ای   
axtaršenâsi-ye kore-yi

Fr.: astronomie sphérique   

The branch of astronomy that is concerned with determining the apparent positions and motions of celestial bodies on the celestial sphere. Same as → positional astronomy.

spherical; → astronomy.

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