Fr.: binaire astrométrique
A binary star in which the presence of an unresolved companion is revealed by small oscillations in the movement of the visible component caused by the gravitational influence of the unseen component.
→ astrometry; → binary.
Not having → symmetry.
automatic photometric telescope
durbin-e šidsanjik-e xodkâr, teleskop-e ~ ~
Fr.: télescope photométrique automatique
A telescope developed to perform photometric observations automatically.
→ automatic; → photometric; → telescope.
hamâmun-e âse-yi, âse-hamâmun
Having → axisymmetry.
qânun-e fešârsanji, ~ fešârsanjik
Fr.: loi barométrique
A law which describes the vertical pressure distribution in the lower parts of Earth's atmosphere. The atmospheric pressure decreases exponentially from any reference surface as the altitude increases.
Of or relating to or measured by a → bolometer.
aršâyeš-e tafsanji, ~ tafsanjik
Fr.: correction bolométrique
The difference between the → visual magnitude and → bolometric magnitude.
→ bolometric; → correction.
tâbandegi-ye tafsanji, ~ tafsanjik
Fr.: luminosité bolométrique
The total rate of energy output of an object integrated over all wavelengths.
→ bolometric; → luminosity.
borz-e tafsanji, ~ tafsanjik
Fr.: magnitude bolométrique
The magnitude of an astronomical object for the entire range of its electromagnetic spectrum.
→ bolometric; → magnitude.
mowj-e desimetri (#)
Fr.: onde décimétrique
An electromagnetic radio wave having wavelengths between 10 cm and 1m, corresponding to a frequency between 300 and 3,000 Mega Hertz. It is naturally emitted by various astronomical objects.
Decimetric, from → deci- + from Fr. métrique, → metric; → wave.
Mowj, → wave; desimetri, from décimétrique, as above.
Of or pertaining to geometry or to the principles of geometry.
Adj. of → geometry
Fr.: albedo géométrique
A measure of the → reflectivity of a surface, especially of the solar system bodies (planets, satellites or asteroids). It is the ratio of a body's brightness at zero → phase angle to the brightness of a perfectly diffusing disk with the same position and apparent size as the body. Geometric albedo depends on the radiation wavelength. The bolometric geometric albedo refers to reflectivity in all wavelengths. Compare with the → Bond albedo.
Fr.: retard géométrique
One of the two factors contributing to → gravitational lensing time delay that arises from the fact that the bent trajectory is longer than the straight one. The other factor is due to the → Shapiro time delay.
Fr.: horizon géométrique
Where the apparent → sea horizon would be if there were no → atmospheric refraction.
miyângin-e hendesi (#)
Fr.: moyenne géométrique
The middle term in a → geometric progression. Of two terms, the geometric mean is the square root of their product. For example, the geometric mean of 4 and 9 is ± 6. For a series of n terms, it is expressed as: (a1.a2. ... .an)1/n.
Fr.: optique géométrique
A branch of physics that deals with reflection and refraction of rays of light without reference to the wave or physical nature of light.
farâyâsi-e hendesi (#)
Fr.: progression géométrique
A → sequence in which the ratio of a term to its predecessor is the same for all terms. In general, the nth term has the form ar(n-1), where n is a positive integer, and a and r are nonzero constants; r is called the ratio or common ratio. The sum of the first n terms is given by: Sn = a(1 - rn)/(1 - r). Also called → geometric sequence.
→ geometric; → progression.
Fr.: diffusion géométrique
A type of scattering in which the wavelength (of the light or the sound) is much smaller than the size of object causing the scattering.
→ geometric; → scattering.
Fr.: suite géométrique
roxgard-e hendesi (#)
Fr.: libration géométrique
Libration resulting from changes in the location of the observer with respect to body. More specifically, a lunar libration motion that results from the Earth based observer seeing the Moon from different directions at different times. There are three types of geometrical libration: → libration in longitude, → libration in latitude, and → diurnal libration. See also → physical libration.