An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 672
main diagonal
  تراکنج ِ فریست   
tarâkonj-e farist

Fr.: diagonale principale   

In the n x n → matrix , the entities a11, a22, ..., ann.

main; → diagonal.

main lobe
  لپ ِ فریست   
lap-e farist

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.

main; → lobe.

Main Ring
  حلقه‌ی ِ فریست   
halqe-ye farist

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,

main; → ring.

main sequence
  رشته‌ی ِ فریست   
ršte-ye farist

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).

main; → sequence.

main-sequence fitting
  سزکرد ِ رشته‌ی ِ فریست   
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.

main sequence; → fitting.

main-sequence turnoff
  رهگشت ِ رشته‌ی ِ فریست   
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.

main sequence; → turnoff.

mehin (#)

Fr.: majeur   

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.

major axis
  آسه‌ی ِ مهین   
âse-ye mehin

Fr.: grand axe   

The greatest diameter of an ellipse; it passes through the two foci.

major; → axis.

major merger
  تشک ِ مهین   
tašk-e mehin

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.

major; → merger.

major planet
  سیاره‌ی ِ مهین   
sayyâre-ye mehin

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.

major; → planète.

major premise
  پیشپایه‌ی ِ مهین   
pišpâye-ye mehin

Fr.: prémisse majeur   

Logic: In a → categorical syllogism, the premise containing the → major term.

major; → premisse.

major term
  ترم ِ مهین   
tarm-e mehin

Fr.: terme majeur   

Logic: In a → syllogism, the → predicate of the → conclusion which occurs in the → major premise.

major; → term.


Fr.: majorant   

A function, or an element of a set, that dominates others or is greater than all others. In other words, for a function f defined on the interval I, the point M such that for each x on I, f(x)≤ M. See also → minorant.

From Fr. majorant, from majorer "to increase, raise," from L. → major.

Mehân, from mehidan, from meh "great, large," → major.

mehini (#)

Fr.: majorité   

The greater number, part, or quantity of a whole.

major; → -ity.


Fr.: Makemake   

The third largest known → dwarf planet after → Eris and → Pluto. Numbered 136472, and initially called 2005 FYg, it belongs to the → Kuiper belt in the solar system. Discovered in 2005, Makemake is roughly three-quarters of Pluto in size and orbits the Sun in about 310 years.

Named after Makemake "the creator of humanity and god of fertility" in the mythology of the Rapanui, the native people of Easter Island.

Maksutov telescope
  دوربین ِ ماکسوتوف، تلسکوپ ِ ~   
durbin-e Maksutof, teleskop-e ~ (#)

Fr.: télescope de Maksutov   

A → reflecting telescope incorporating a deeply curved → meniscus, → lens, which corrects the → optical aberrations of the spherical → primary mirror to give high-quality → images over a wide → field of view.

Named for the Russian optical specialist Dmitri Maksutov (1896-1964), who developed the design; → telescope.

Malmquist bias
  ورک ِ مالمکوییست   
varak-e Malmquist

Fr.: biais de Malmquist   

A selection effect in observational astronomy. If a sample of objects (galaxies, quasars, stars, etc.) is flux-limited, then the observer will see an increase in average luminosity with distance, because the less luminous sources at large distances will not be detected.

Named after the Swedish astronomer Gunnar Malmquist (1893-1982); → bias.

Malmquist correction
  ارشایش ِ مالمکوییست   
aršâyeš-e Malmquist

Fr.: correction de Malmquist   

A correction introduced into star counts distributed by apparent magnitude.

Malmquist bias; → correction.

Malus' law
  قانون ِ مالوس   
qânun-e Malus (#)

Fr.: loi de Malus   

If the light wave entering an → analyzer is → linearly polarized, the intensity of the wave emerging from the analyzer is I = k I0 cos2φ, where k is the coefficient of transmission of the analyzer, I0 is the intensity of the incident light, and φ is the angle between the planes of → polarization of the incident light and the light emerging from the analyzer.

Named after Etienne Louis Malus (1775-1812), French physicist who also discovered polarization by reflection at a glass surface (1808); → law.

Mamun's method
  روش ِ مأمون   
raveš-e M'amun

Fr.: méthod de Mamun   

A method for deriving the Earth's size based on measuring a length of meridian between two points corresponding to the difference between the respective latitudes. The Abbasid caliph al-Ma'mun (ruling from 813 to 833 A.D.), appointed two teams of surveyors to this task. They departed from a place in the desert of Sinjad (nineteen farsangs from Mosul and forty-three from Samarra), heading north and south, respectively. They proceeded until they found that the height of the Sun at noon had increased (or decreased) by one degree compared to that for the starting point. Knowing the variation of the Sun's → declination due to its apparent → annual motion, they could relate the length of the arc of meridian to the difference between the latitudes of the two places. They repeated the measurement a second time, and so found that the length of one degree of latitude is somewhat between 56 and 57 Arabic miles (Biruni, Tahdid). 360 times this number yielded the Earth's circumference, and from it the radius was deduced.
See also: → Eratosthenes' method, → Biruni's method.

The seventh Abbasid caliph Abu Ja'far Abdullâh al-Ma'mûn, son of Hârûn al-Rashîd (786-833 A.D.); → method.

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