An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 4 Search : gray
gray
  خاکستری   
xâkestari (#)

Fr.: gris   

(n.) A color between white and black. (adj.) Having a neutral hue.

M.E., O.E. græg, from P.Gmc. *græwyaz; cf. O.N. grar, O.Fris. gre, Du. graw, Ger. grau; Frank. *gris, Fr. gris.

Xâkestari, "ash-colored," from xâkestar "ashes," from Mid.Pers. *xâkâtur, from xâk "earth, dust" + âtur "fire," varaint âtaxš (Mod.Pers. âtaš, âzar, taš), from Av. ātar-, āθr- "fire," singular nominative ātarš-; O.Pers. ātar- "fire;" Av. āθaurvan- "fire priest;" Skt. átharvan- "fire priest;" cf. L. ater "black" ("blackened by fire"); Arm. airem "burns;" Serb. vatra "fire;" PIE base *āter- "fire."

gray (Gy)
  گری   
gray

Fr.: gray   

An SI unit of absorbed radiation dose. One gray is equivalent to an energy absorption of 1 → joule/kg. It has replaced the → rad (rd), an older standard. One gray is equivalent to 100 rad.

Named for Louis Harold Gray (1905-1965), British radiologist and the pioneer of use of radiation in cancer treatment.

gray atmosphere
  جّو ِ خاکستری، هواسپهر ِ ~   
javv-e xâkestari, havâsepher-e ~

Fr.: atmosphère grise   

A simplifying assumption in the models of stellar atmosphere, according to which the absorption coefficient has the same value at all wavelengths.

gray; → atmosphere.

gray body
  جسم ِ خاکستری   
jesm-e xâkestari (#)

Fr.: corps gris   

A hypothetical body which emits radiation at each wavelength in a constant ratio, less than unity, to that emitted by a black body at the same temperature.

gray; → body.