An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 24 Search : precession
precessional
  پیشایانی   
pišâyâni

Fr.: précessionnel   

Of or pertaing to → precession.

precession; → -al.

precessional circle
  پرهون ِ پیشایانی   
parhun-e pišâyâni

Fr.: circle précessionnel   

The path of either → celestial poles around the → ecliptic pole due to the → precession of equinox. It takes about 26,000 years for the celestial pole to complete path.

precessional; → circle.

relativistic precession
  پیشایان ِ بازانیگی‌مند   
pišâyân-e bâzânigimand

Fr.: précession relativiste   

A → general relativistic phenomenon in which the line joining the → apsides of an orbit gradually rotates in a → prograde direction. Also called the → orbital precession and → perihelion precession. Although the general relativistic precession of Mercury's orbit is extremely small, the similar precession observed in the orbit of the → binary pulsar PSR B1913+16 amounts to 4.23 degrees per year, i.e. 36,000 times greater than the → advance of perihelion of Mercury.

relativistic; → precession.

relativistic spin precession
  پیشایان ِ آسه‌ی ِ چرخش ِ بازانیگی‌مند   
pišâyân-e âse-ye carxeš-e bâzânigi-mand

Fr.: précession de l'axe de rotation relativiste   

The change in the direction of the → rotation axis of a → pulsar in a → binary pulsar. In such a system, → geodetic precession leads to a relativistic → spin-orbit coupling, analogous of → spin-orbit coupling in atomic physics. In consequence, the pulsar spin precesses about the total → angular momentum, changing the relative → orientation of the pulsar toward Earth (Damour & Ruffini, 1974). As a result, the angle between the pulsar → rotation axis and our → line of sight changes with time, so that different portions of the emission beam can be observed leading to changes in the measured pulse profile. In extreme cases, the precession may even move the beam out of our line of sight and the pulsar may disappear as predicted for PSR 1913+16 for the year 2025.

relativistic; → spin; → precession.

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