# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 7 Search : Bessel
 Bessel   بسل   BeselFr.: Bessel   From Friedrich Wilhelm Bessel (1784-1846), German astronomer and mathematicians, who made fundamental contributions to positional and spherical astronomy. Bessel equation   هموگش ِ بسل   hamugeš-e BeselFr.: équation de Bessel   A linear second-order differential equation, the solutions to which are called Bessel functions.From → Bessel; → equationHamugeš, → equation. Bessel's star   ستاره‌ی ِ بسل   setâre-ye BesselFr.: étoile de Bessel   Same as → 61 Cygni, the first star whose distance was measured, by Friedrich Bessel in 1838.→ Bessel; → star. Besselian   بسلی   BesseliFr.: besselien, de Bessel   Of or pertaining to Friedrich Wilhelm Bessel (1784-1846) or to his discoveries. → Besselian day number → → Bessel equation → Besselian star constant → → Besselian year.→ Bessel. Besselian day number   شماره‌ی ِ روز ِ بسلی   šomâre-ye ruz-e BesseliFr.:   Any of the five quantities denoted by A, B, C, D, and E used in conjunction with → Besselian star constants for the reduction of a star's → mean catalog place to its → apparent place.→ Besselian; → day; → number. Besselian star constant   پایای ِ اختری ِ بسلی   pâyâ-ye axtari-ye BesseliFr.: constante stellaire besselienne   Any of the eight quantities denoted by a, b, c, d (for → right ascension) and a', b', c', d' (for → declination) used in conjunction with → Besselian day numbers for the reduction of star's → mean catalog place.→ Besselian; → star; → constant. Besselian year   سال ِ بسلی   sâl-e BeseliFr.: année besselienne   The period taken for the right ascension of the mean Sun to increase by 24 hours. The starting point is when the mean Sun's longitude is 280°, corresponding roughly to January 1. It is virtually the same as the tropical year.→ Besselian; → year.