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: 5 Search : jump
Balmer jump
  جهش ِ بالمر   
jaheš-e Bâlmer

Fr.: saut de Balmer   

Same as → Balmer discontinuity.

Balmer; → jump.

bistability jump
  جهش ِ دو-پایداری   
jaheš-e do-pâydâri

Fr.: bistabilité par saut   

An abrupt discontinuity in the → stellar wind properties of → hot stars near → effective temperatures about 21,000 K and 10,000 K, corresponding to O9.5-B3 supergiants (Castor et al. 1975, ApJ 195, 157; Lamers et al., 1995, ApJ 455, 269). At these temperatures the → terminal velocity of the wind drops steeply by about a factor two and the → mass loss rate increases steeply by about a factor three to five, when going from high to low temperatures. Bistability jump is related to the degree of ionization in the wind. With a little drop in the temperature, the dominant driving element (Fe) will recombine to lower ionization stages which produces a lower terminal velocity and a relatively high density in the wind. → wind momentum. Additional bistability jumps may occur at higher temperatures where CNO may provide the dominant line driving, especially for low metallicity stars (Vink et al. 2001, A&A 369, 574). However, a recent study using a larger sample finds that there is a gradual decline in the wind terminal velocities of early B supergiants and not a "jump" (Crowther et al. 2006, A&A 446, 279).

bistability; → jump.

jump
  جهش   
jaheš (#)

Fr.: saut   

A point of discontinuity in a function or a derivative of a function.

Etymology unclear, probably akin to L.G. gumpen "to jump."

Jaheš, verbal noun of jahidan, jastan "to jump, to leap," from Mid.Pers. jastan, jahidan "to jump," figuratively "to happen, occur;" Av. yaēš-, yas- "to boil;" cf. Skt. yas-, yásyati "to boil, to heat; to make effort."

jump conditions
  بوتارهای ِ جهش   
butârhâ-ye jaheš

Fr.: conditions de saut   

Very different values of pressure and density (or temperature or energy) across a shock wave.

jump; → condition.

quantum jump
  جهش ِ کو‌آنتومی   
jaheš-e kuântomi

Fr.: saut quantique   

The transition of a quantum system from one stationary state to another, accompanied by absorption or emission of energy.

quantum; → jump.