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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 Moon Spot (SMS)
lake-ye sodiomi-ye Mâng
Fr.: tache de sodium de la Lune
The → sodium tail of the Moon as it appears in the sky opposite the Sun. The SMS undergoes changes in shape and brightness. It is brighter when the → new moon occurs at → perigee, when the new moon is north of the → ecliptic, and approximately five hours after the new moon.
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.
sodium tail of the Moon
donbâle-ye sodiomi-ye Mâng
Fr.: queue de sodium de la Lune
A comet-like tail of the Moon comprised of → sodium (Na) atoms and invisible to the naked eye. The lunar surface is constantly bombarded by the → solar wind, → photons, and → meteoroids, which can liberate Na atoms from the → regolith. These atoms are subsequently accelerated by solar → radiation pressure to form a long comet-like tail opposite the Sun. Near → new moon, this diffuse cloud of Na atoms encounters the Earth's gravity and is "pinched" into a beam of enhanced density. This beam appears as the ~3° diameter Sodium Moon Spot (SMS) seen in the sky opposite the Sun. The spot is about five times the diameter of the → full moon, and is 50 times fainter than can be seen with the unaided eye. The spot is reflected light from millions of Na atoms that two days earlier were on the surface of the Moon. This spot is visible to sensitive cameras equipped with filters tuned to the orange light emitted by Na atoms near 589.3 nm (Baumgardner et al., 2021 Journal of Geophysical Research: Planets DOI: 10.1029/2020je006671).
M.E. softe "yielding, gentle, mild;" O.E. softe "gentle, easy;" cf. O.S. safti, O.H.G. semfti, Ger. sanft, M.Du. sachte, Du. zacht.
Narm "soft; smooth; mild," from Mid.Pers. narm "soft; humble."
Fr.: binaire mou
In → stellar dynamics studies of → three-body encounters, a → binary system whose → binding energy is smaller than the typical → kinetic energy of the relative motion of an incoming third body. See also → hard binary.
soft gamma repeater (SGR)
bâzgaršgar-e gâmmâ-ye narm
Fr.: répéteur gamma mou
A member of a small class of objects which emit intense bursts of → gamma rays and → X-rays (> 100 keV) at irregular intervals. The bursts last for some 100 milli-seconds. It is conjectured that they are → magnetars. See also → starquake.
soft gamma-ray repeater (SGR)
bâzgaršgar-e partowhâ-ye gâmmâ-ye narm
Fr.: répéteur des rayons gamma mous
Same as → soft gamma repeater (SGR).
Fr.: fer doux
Fr.: voile du palais, palais mou, velum
Soft X-ray Transient (SXT)
gozarâ-ye partow-e X-e narm
An → X-ray binary system that has a long period of → quiescence interrupted by → outbursts of low-energy → soft X-rays. Alternatively known as X-ray novae, the majority (~ 75%) of SXTs contain a → black hole and a low-mass → main sequence → companion star in orbit around one another. It is thought that SXTs arise in a similar manner to → dwarf novae, through instabilities in the → accretion disk around the → compact object (→ disk instability model).
partowhâ-ye iks-e narm
Fr.: rayons X mous
X-ray photons with energies between about 0.1 to 10 keV. → hard X-rays.
A general term used to describe a collection of computer programs, procedures, and documentation that perform some tasks on a computer system. → hardware.
→ soft + ware, from M.E., from O.E. waru, from P.Gmc. *waro (cf. Swed. vara, Dan. vare, M.Du. were, Du. waar, Ger. Ware "goods").
Narm, → soft + afzâr "instrument, means, tool," from Mid.Pers. afzâr, abzâr, awzâr "instrument, means," Proto-Iranian *abi-cāra- or *upa-cāra-, from cāra-, cf. Av. cārā- "instrument, device, means" (Mid.Pers. câr, cârag "means, remedy;" loaned into Arm. aucar, aucan "instrument, remedy;" Mod.Pers. câré "remedy, cure, help"), from kar- "to do, make, build;" kərənaoiti "he makes" (Pers. kardan, kard- "to do, to make"); cf. Skt. kr- "to do, to make," krnoti "he makes, he does," karoti "he makes, he does," karma "act, deed;" PIE base kwer- "to do, to make").
Fr.: architecture de logiciel
The overall structure of a software system consisting of mutually dependent components that create a logical whole.
Fr.: terre, sol
All loose, unconsolidated earth and organic materials above bedrock that support plant growth.
M.E. soile, O.Fr. soil "piece of ground, place," from L. solium "seat," meaning confused with that of L. solum "soil, ground."
Xâk, from Mid.Pers. xâk "earth, dust," ultimately from Proto-Ir. *āika-, from *āi- "earth, soil," cf. Av. āi- "earth, soil," Gk. aia "earth, land," + suffix -ka. The initial x- is a prothesis, as in xâya "egg" (Gershevitch 1962).
Fr.: jour solaire martien
The solar day on Mars, which has a mean period of 24 hours 39 minutes 35.244 seconds (based on SI units), about 2.7% longer than Earth's solar day. The Martian sidereal day, as measured with respect to the fixed stars, is 24h 37m 22.663s, as compared with 23h 56m 04.0905s for Earth.
Sol, from L. sol "sun," cognate with Pers. hur, → Sun.
Of or pertaining to the Sun.
Adjective from L. sol; → Sun.
Fr.: abondance solaire
Fr.: activité solaire
solar activity cycle
carxe-ye žirandegi-ye xoršid
Fr.: cycle d'activité solaire
Same as the → solar cycle.