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: 2 Search : sodium
sodium
  سودیوم   
sodiom (#)

Fr.: sodium   

A metallic chemical element; symbol Na (L. natrium]. Atomic number 11; atomic weight 22.98977; melting point 97.81°C; boiling point 892.9°C; specific gravity 0.971 at 20°C. It was discovered in 1807 by the English chemist Humphry Davy from electrolysis of caustic soda (NaOH).

Sodium, from soda (NaOH).

sodium tail
  دم ِ سودیومی   
dom-e sodiomi

Fr.: queue de sodium   

1) A kind of → cometary tail appearing in some → comets, such as → Hale-Bopp. Sodium tails arise from the very strong → fluorescence of their sodium atom → D lines in the visible. They are rapidly accelerated to high velocities by the Sun, forming a very straight tail distinct from the → ion tail. The release mechanism of sodium from comets is still a matter of debate. Also called → neutral tail.
2) An enormous, comet-like tail of sodium gas stretching out behind the Moon, at least 800,000 km (many hundreds, and perhaps thousands, of lunar radii). The tail is due to the strong influence of the Sun's → radiation pressure on sodium atoms (→ D line) present in the → lunar exosphere. Near → new Moon phase, the extended lunar sodium tail can be observed as it sweeps over the Earth and is gravitationally focused into a visible sodium "spot" in the → anti-solar direction. It is too faint to be detected by the human eye.

sodium; → tail.