tavân-e bozorgnemâyi (#)
The ratio between the focal lengths of the objective and ocular in a telescope.
borz, qadr (#)
A measure of brightness in astronomy on a → logarithmic scale in which a difference of five magnitudes represents a difference of 100 times in brightness. In this scale the lower a magnitude, the brighter the object. The faintest magnitude reached by → unaided eye is 6.
From L. magnitudo "greatness, bulk, size," from magnus "great," cognate with Pers. meh "great, large" (Mid.Pers. meh, mas; Av. maz-, masan-, mazant- "great, important," mazan- "greatness, majesty," mazišta- "greatest;" cf. Skt. mah-, mahant-; Gk. megas; PIE *meg- "great") + -tudo, suffix forming abstract nouns from adjectives and participles.
Borz "height, magnitude" (it occurs also in the name of the mountain chain Alborz), related to boland "high," bâlâ "up, above, high, elevated, height," berg "mountain, hill" (Mid.Pers. buland "high;" O.Pers. baršan- "height;" Av. barəz- "high, mount," barezan- "height;" cf. Skt. bhrant- "high;" L. fortis "strong" (Fr. & E. force); O.E. burg, burh "castle, fortified place," from P.Gmc. *burgs "fortress;" Ger. Burg "castle," Goth. baurgs "city," E. burg, borough, Fr. bourgeois, bourgeoisie, faubourg); PIE base *bhergh- "high"). Qadr, from Ar.
Fr.: échelle de magnitudes
A scale for measuring and comparing the brightness of astronomical objects.
bardid bâ borz-e haddmand
Fr.: relevé limité en magnitude
A survey in which the observed objects are bighter than a given → apparent magnitude.
Fr.: force de Magnus
The force exerted on a spinning object moving through a fluid medium in virtue of → Bernoulli's theorem. The Magnus force can deviate a football from its path when a player strikes it so that it spins about an axis perpendicular to the flow of air around it. As the spinning ball moves through the air, it will create a pressure difference between its two sides. The air travels faster relative to the centre of the ball where its periphery is moving in the same direction as the airflow. This reduces the pressure according Bernoulli's theorem. The opposite effect happens on the other side of the ball, where the air travels slower relative to the centre of the ball. There is therefore an imbalance in the forces that will curve the ball's trajectory.
Named after Heinrich Gustav Magnus (1802-1870), a German chemist and physicist; → force.
Chief in size, extent, or importance; leading; → principal.
From M.E. meyn, mayn "strength, power," from O.E. mægen "power, strength, force," from P.Gmc. *maginam- "power," from *mag- "to be able, have power."
Farist, literally "foremost" (cf. Mid.Pers. frahist "main, principal, first, much"), from far-, Mid.Pers. fra-; O.Pers. fra- "forward, forth;" Av. frā "forth," pouruua- "first"; cf. Skt. pūrva- "first," pra- "before, formerly;" Gk. pro; L. pro; O.E. fyrst "foremost," superlative of fore, E. fore + -est superlative suffix, Mid.Pers. -ist, -išt-; Av. -išta-, cf. Skt. -istha-, Gk. -istos, O.H.G. -isto, -osto, O.E. -st, -est, -ost.
Fr.: lobe principal
Same as → main lobe.
Fr.: ceinture principale
Fr.: diagonale principale
In the n x n → matrix , the entities a11, a22, ..., ann.
Fr.: lobe principal
The lobe in the reception pattern of a radio telescope that includes the region of the maximum received power. Also called major lobe and main beam.
Fr.: anneau principal
A thin strand of material encircling Jupiter; the main component in → Jupiter's ring system of three parts. The diffuse innermost boundary begins at approximately 123,000 km. The main ring's outer radius is found to be at 128,940 km,
Fr.: séquence principale
An evolutionary stage in the life of a star when it generates its energy by the conversion of hydrogen to helium via → nuclear fusion in its core. Stars spend 90% of their life on the main sequence. On the → Hertzsprung-Russell diagram it appears as a track running from top left (high temperature, high luminosity, high mass) to lower right (low temperature, low luminosity, low mass). See also → zero age main sequence (ZAMS), → terminal age main sequence (TAMS).
sazkard-e reshteh-ye farist
Fr.: ajustement par la séquence principale
The method of determining the distance to a star cluster by overlaying its main sequence on the theoretical zero-age main sequence and noting the difference between the cluster's apparent magnitude and the zero-age main sequence's absolute magnitude.
rahgašt-e rešte-ye farist
Fr.: tournant final de la séquence principale
The point on the → Hertzsprung-Russell diagram of a star cluster at which stars begin to leave the → main sequence and move toward the → red giant branch. The main-sequence turnoff is a measure of age. In general, the older a star cluster, the fainter the main-sequence turnoff. Same as → turnoff point.
Greater in size, extent, or importance.
M.E. majour, from O.Fr., from L. major, irregular comparative of magnus "large, great," cognate with Pers. meh "large, great," as below.
Mehin comparative and superlative of meh "great, large" (Mid.Pers. meh, mas; Av. maz-, masan-, mazant- "great, important," mazan- "greatness, majesty," mazišta- "greatest;" cf. Skt. mah-, mahant-; Gk. megas; PIE *meg- "great") + -in superlative suffix.
Fr.: grand axe
The greatest diameter of an ellipse; it passes through the two foci.
Fr.: fusion majeure
The → merging of two spiral galaxies with roughly equal masses colliding at appropriate angles. The dynamical friction is so efficient that the galaxies merge after only a few perigalactic passages.
Fr.: planète majeure
A name used to describe any planet that is considerably larger and more massive than the Earth, and contains large quantities of hydrogen and helium. Jupiter and Neptune are examples of major planets.
Fr.: prémisse majeur
Fr.: terme majeur