apparent sidereal day
ruz-e axtari-ye padidâr
Fr.: jour sidéral apparent
apparent sidereal time
zamân-e axtari-ye padidâr
Fr.: temps sidéral apparent
The → mean sidereal time corrected for the → nutation and shift in the obliquity of the ecliptic that occurs as a result of the Moon's gravitational effect. Apparent sidereal time differs from mean sidereal time in that the → true vernal equinox point is used.
apsides, line of
Fr.: ligne des apsides
The line connecting the two apsides, i.e. the major axis of an elliptical orbit. → apsis.
apsis (pl. apsides)
L. apsis "arch, vault," from Gk. hapsis "loop, arch," from haptein "fasten together".
Mod.Pers. habâk "top of the head; the summit of a mountain".
To think carefully about, especially in order to make a decision; contemplate; reflect on (dictionary.com).
M.E. consideren, from O.Fr. considerer "reflect on, study," from L. considerare "to examine, look at closely," literally "to observe the stars," from → com- "with" + sider (stem of sidus) "star, group of stars," → sideral.
Âgâridan, from intensive prefix â- + gâr-, variants gar-, gâl- "to consider, observe," as in engâridan "to suppose," negaristan "to observe, look, notice," segâl "thought," segâlidan "to think, meditate," ultimately from Proto-Iranian *kar- "to observe, to consider;" cf. Av. kar- "to remember; to impress on memory;" Skt. kal- "to observe, consider," kalayati "considers, observes."
1) Rather large or great in size, distance, extent, etc.
The act or an instance of considering.
A rural area; he inhabitants of a countryside.
Rustâ, from Mid.Pers. rôstâk, rôtastâk "village, district, river-bed;" loaned into Armenian rotstak, ərotastak "district."
Greenwich Apparent Sidereal Time (GAST)
zamân-e axtari-ye padidâr-e Greenwich
Fr.: temps sidéral apparent de Greenwich
Greenwich Mean Sidereal Time (GMST)
zamân-e axtari-ye miyângin-e Greenwich
Fr.: temps sidéral moyen de Greenwich
Greenwich sidereal date
ruz-e axtari-ye Greenwich
Fr.: jour sidéeal de Greenwich
Greenwich sidereal day number
šomâre-ye ruz-e axtari-ye Greenwich
Fr.: nombre du jour sidéral de Greenwich
The integral part of the → Greenwich sidereal date.
lâye-ye Heaviside (#)
Fr.: couche de Heaviside
English physicist Oliver Heaviside (1850-1925).
highly siderophile element (HSE)
bonpâr-e besyâr âhandust
Fr.: élément hautement sidérophile
A → chemical element that is → geochemically characterized as having a strong → affinity to partition into → metals relative to → silicates. The highly siderophile elements, → ruthenium (Ru), → rhodium (Rh), → palladium (Pd), → rhenium (Re), → osmium (Os), → iridium (Ir), → platinum (Pt), and → gold (Au), are of interest to planetary scientists because they give insights into the early history of → accretion and → differentiation. HSEs prefer to reside in the metal of planetary cores. Therefore, the HSEs found in planetary → mantles are considered to be overabundant relative to their known preferences for metal over silicate. Therefore, it has been inferred that processes other than → equilibrium partitioning have been responsible for establishing the abundances of → mantle siderophiles. A detailed understanding of the absolute → concentrations and relative abundances of the HSEs may therefore give important insights into the earliest history of a planet (Jones et al., 2003, Chemical Geology 196, 21).
From Gk. sidero-, from sideros "iron" + → -phile.
lâye-ye Kennelly-Heaviside (#)
Fr.: couche de Kennelly-Heaviside
One of several layers in the Earth's ionosphere occurring at 90-150 km above the ground. It reflects medium-frequency radio waves whereby radio waves can be propagated beyond the horizon.
Named after the American electrical engineer Arthur Edwin Kennelly (1861-1939) and the English physicist Oliver Heaviside (1850-1925), who independently predicted the existence of the reflecting layer in 1902; → layer.
line of apsides
Fr.: ligne des apsides
local sidereal time
zamân-e axtari-ye mahali
Fr.: temps sidéral local
Local time measured by the apparent motion of the stars. It is the most useful form of sidereal time since it gives the right ascension of a transiting celestial object at a given location.
lunar far side
ruy-e dur-e mâng
Fr.: face cachée de la Lune
The Moon's hemisphere which is not visible from the Earth. The Moon always shows the same face to the Earth, because Earth and Moon are → tidally locked. This means that the period of → lunar rotation on it axis is the same as its sidereal revolution period around the Earth (→ sidereal month). In other words, the Moon is in → synchronous rotation with the Earth. As a result, the same side always faces the Earth. To be more precise, taking the lunar → libration into account, the Moon presents about 59% of its surface to Earth. → libration in longitude, → libration in latitude, → physical libration, → geometrical libration.
lunar sidereal orbital period
dowre-ye madâri-ye axtari-ye mâng
Fr.: période orbitale sidérale de la Lune
Same as → sidereal month.
mean sidereal day
ruz-e axtari-ye miyângin
Fr.: jour sidéral moyen