An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

   Homepage   
   


A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

<< < ape per > >>

Number of Results: 39 Search : period
periodic wave
  موج ِ دوره‌ای   
mowj-e dowre-yi

Fr.: onde périodique   

An oscillatory motion in which each point is repeatedly displaced at equal time intervals.

periodic + → wave.

periodical
  دوره‌ای   
dowreyi (#)

Fr.: périodique   

Same as → periodic.

periodic; → -al.

periodically variable supergiant (PVSG)
  ابرغول ِ ورتنده‌ی ِ دوره‌ای   
abarqul-e vartande-ye dowreyi

Fr.: supergéante variable périodiquement   

A variable → supergiant star with typical periods of the order of 10 to 100 days and amplitudes less than a few tenths of a magnitude. PVSGs are thought to be pulsating → g modes, caused by a density inversion, arising from an → opacity bump, most likely from Fe, H, and/or He.

periodical; → -ly; → variable; → supergiant.

periodicity
  دوره‌ایگی   
dowreigi

Fr.: périodicité   

A state or condition characterized by regular repetition in time or space.

periodic + → -ity.

periodogram
  دوره‌نگاشت   
dowrenegâšt

Fr.: périodogramme   

A plot for examining frequency-domain data in an equi-spaced → time series. The periodogram is the → Fourier transform of the → autocovariance function. The periodogram method relies on the definition of the → power spectral density .

period; + euphonic infix -o-; → -gram.

precession period
  دوره‌ی ِ پیشایان   
dowre-ye pišâyân

Fr.: période de précession   

The interval with which a rotating body precesses. The precession period of the Earth is 25,770 years. For a → spinning top it is given by: Tp = (4π2I)/(mgrTs), where I is the → moment of inertia, m the mass of the top, g gravity, r the distance between the center of mass and the contact point, and Ts is the spinning period of the top.

precession; → period.

quasiperiodic motion
  جنبش ِ چونان-دوره‌ای   
jonbeš-e cunân-dowreyi

Fr.: mouvement quasipériodique   

In a dynamical system, a form of motion that is regular but never exactly repeating. Quasiperiodic motion appears when the system contains two or more incommensurate frequencies.

quasi-; → periodic; → motion.

Quaternary period
  دوران ِ چهارم   
dowrân-e cahârom

Fr.: quaternaire   

The last two million years of geologic time, comprising the Pleistocene and Holocene glacial epochs. Estimates of the date of the beginning of the Quaternary vary between 2.5 and 1.6 million years ago.

Quaternary, from L. quaternarius "consisting of four," from quatern(i) "fourt at a time" + -arius "-ary;" → period.

Dowrân, → period; cahârom "fourth," from cahâr "four" + -om "-th."

rotation period
  دوره‌ی ِ چرخش   
dowre-ye carxeš (#)

Fr.: période de rotation   

The interval of time during which an object turns once about its axis.

rotation; → period.

rotational period
  دوره‌ی ِ چرخش   
dowre-ye carxeš

Fr.: période de rotation   

rotation period.

rotational; → period.

short-period comet
  دنباله‌دار ِ کوتاه-دوره   
dombâledâr-e kutâh-dowré

Fr.: comète à courte période   

A comet with a period less than 200 years. Same as → periodic comet.

short; → period; → comet.

short-period variable
  ورتنده‌ی ِ کوتاه-دوره   
vartande-ye kutâh-dowré

Fr.: variable à courte période   

A variable star that has a relatively short period with respect to stars of similar types.

short; → period; → variable.

sidereal period
  دوره‌ی ِ اختری   
dowre-ye axtari (#)

Fr.: période sidérale   

sidereal revolution period; → sidereal rotation period.

sidereal; → period.

sidereal revolution period
  دوره‌ی ِ گردش ِ اختری   
dowre-ye gardeš-e axtari (#)

Fr.: période de révolution sidérale   

The time taken by a planet or satellite to complete one revolution about its primary with respect to stars. For Earth, same as → sidereal year.

sidereal; → revolution; → period.

sidereal rotation period
  دوره‌ی ِ چرخش ِ اختری   
dowre-ye carxeš-e axtari

Fr.: période de rotation sidérale   

The rotation period of a celestial body with respect to fixed stars. For Earth, same as → sidereal day.

sidereal; → rotation; → period.

Sothic period
  دوره‌ی ِ تیشتری   
dowre-ye Tištari

Fr.: période sothique   

The interval after which the heliacal rising of the star Sirius occurs at the same time of the year. It is a period of 1,460 Sothic years.

From Fr. sothique, from Gk. Sothis, an Egyptian name of Sirius; → period.

Tištari, of or pertaining to Tištarserius; dowré, → period.

synodic period
  دوره‌ی ِ هماگمی   
dowre-ye hamâgami

Fr.: période synodique   

1) For planets, the mean interval of time between successive → conjunctions of two planets, as observed from the Earth. For → inferior planets (Venus and Mercury):
1/P = 1/E + 1/S.
For → superior planets (Mars, Jupiter, etc.):
1/P = 1/E - 1/S,
where P = → sidereal period of a planet, E = synodic period of the Earth, and S = synodic period of the planet. For example, the synodic period of Jupiter, calculated from the sidereal period of Jupiter (P), 11.856 years, via 1/11.856 = 1/1.0 - 1/S, is 398.9 days.
2) For satellites, the mean interval between successive conjunctions of a satellite with the Sun, as observed from the satellite's → primary.

synodic; → period.

ultrashort-period Cepheid
  کفیءوسی ِ اولتر-کوتاه-دوره   
Kefeid-e ultar-kutâh-dowré

Fr.: céphéide à très courte période   

A → Cepheid star of → spectral type A-F with regular pulsation period of 1-3 hours and with small variations in amplitude. This group is also known as δ Scuti stars.

ultra-; → short; → period; → Cepheid.

Victorian period
  دوره‌ی ِ ویکتوریایی   
dowre-ye Viktoriyâ-yi

Fr.: période victorienne   

A series of 532 years, arising from the cycles of the Sun and Moon multiplied into one another. It was used by the Western churches for many years, in computing the time of Easter, till the → Gregorian calendar was established.

Named after Victorius (a French clergyman), who invented the period about the middle of the 5th century.

<< < ape per > >>