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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 158 Search : ear
shear turbulence
  آشوبناکی ِ کرنی   
âšubnâki-ye karni

Fr.: turbulence de cisaillement   

A type of → instability occurring within a → fluid as a result of the → shear caused by → differential rotation. The condition for shear instability is expressed by the → Richardson criterion. Shear turbulence is likely the most efficient → mixing process in stellar → radiative zones.

shear; → turbulence.

shear wave
  موج ِ کرنی   
mowj-e karni

Fr.: onde de cisaillement   

A wave that occurs in an elastic medium with the disturbances perpendicular to the direction of motion of the wave. Shear waves do not propagate through a fluid. Also called S-wave, secondary wave, and transverse wave.

shear; → wave.

sidereal year
  سال ِ اختری   
sâl-e axtari (#)

Fr.: année sidérale   

The interval between two successive passages of the Sun, in its apparent → annual motion around the → celestial sphere, through a particular point relative to stars. It is equal to 365.256356 days for the J2000.0 epoch and is 20m 24.5s longer than the → tropical year.

sidereal; → year.

snowball Earth
  زمین ِ برف-گوله   
Zamin-e barf-gule

Fr.: Terre boule de neige   

Any of several episodes in the history of the Earth where our planet was entirely covered by glacial ice from pole to pole. There are at least three such episodes. The first one, called the Huronian glaciation, extended from 2.4 billion years ago to 2.1 billion years (lasting about 300 million years). In the last billion years, the Earth has experienced two more global glaciations: the Sturtian glaciation, which began 720 million years ago and, following a brief interglacial episode, the Marinoan glaciation, which ended 635 million years ago. During such episodes the global mean temperature would be about -50°C because most of the Sun's radiation would be reflected back to space by the icy surface. The average equatorial temperature would be about -20°C, roughly similar to present Antarctica. Without the moderating effect of the oceans, temperature fluctuations associated with the day-night and seasonal cycles would be greatly enhanced. Because of its solid surface, the climate on a snowball earth would have much in common with present Mars (http://www.snowballearth.org).

The term snowball Earth was coined in 1989 by Joe Kirschvink, a biomagnetist and paleomagnetist at the Caifornia Institute of Technology in Pasadena, USA; → earth.

solar year
  سال ِ خورشیدی   
sâl-e xoršidi (#)

Fr.: année solaire   

The period of time required for the Earth to make one complete revolution around the Sun. Solar year is a general term for: → tropical year, → vernal equinox year, and → autumnal equinox year, which have different lengths.

solar; → year.

Sothic year
  سال ِ تیشتری   
sâl-e Tištari

Fr.: année sothique   

The Egyptian year of 365 days and 6 hours, as distinguished from them Egyptian vague year, which contained 365 days.

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

Tištari, of or pertaining to Tištarserius; sâl, → year.

super-Earth
  ابر-زمین   
abar-zamin

Fr.: super-Terre   

An → extrasolar planet more massive than the Earth but less massive than 10 → Earth masses. The first discovered super-Earth orbits an M4 V star named GJ 876. Its estimated mass is 7.5±0.7 Earth masses and it has an orbital period of 1.94 days. It is close to the host star, and the surface temperature is calculated to lie between 430 and 650 K (Rivera et al. 2005, ApJ 634, 625).

super-; → Earth.

thermonuclear flash
  درخش ِ گرماهسته‌ای   
deraxš-e garmâhaste-y

Fr.: flash thermonucléaire   

A theoretical interpretation for the → X-ray bursts observed toward → low-mass X-ray binary (LMXB) stars. According to models, X-ray bursts are produced on the surface of → neutron stars as a result of violent thermonuclear processes in a → hydrogen or → helium rich → layer. It is the → nuclear energy released in the → fusion of hydrogen and helium to heavier elements (e.g., Ni, Zn, and Se) in the → accreted matter which heats the upper layers of the neutron star so that X-rays are emitted from the surface (see, e.g., Taam, R.E., 1984, AIP Conf. Proc. 115, 263).

thermonuclear; → flash.

thermonuclear reaction
  واژیرش ِ گرماهسته‌ای   
vâžireš-e garmâhaste-yi (#)

Fr.: réaction thermonucléaire   

A nuclear reaction in which two or more atomic nuclei fuse into a single heavier nucleus by a collision of the interacting particles at extremely high temperatures. Chains of thermonuclear reactions, such as the → proton-proton chain and the → CNO cycle, account for the energy radiated from the Sun and more massive stars.

thermo- + → nuclear; → reaction.

thermonuclear runaway
  واژیرش ِ گرماهسته‌ای ِ لگام گسیخته   
vâžireš-e garmâhaste-yi-e legâm gosixté

Fr.: emballement thermonucléaire   

1) The uncontrolled → fusion of hydrogen into helium.
2) A → thermonuclear reaction process occurring at electron → degenerate conditions in stellar material, such as in → Type Ia supernovae.

thermonuclear; → runaway.

Vâžireš, → reaction; garmâhaste-yi, → thermonuclear; legâm gosixté literally "rampant, unrestrained," from legâm "bridle, rein" + gosixté "broken off, torn away," p.p. of gosixtan "to tear away, to break off."

thermonuclear supernova
  ابر-نو-اختر ِ گرماتوانیک   
abar-now-axtar-e garmâtavânik

Fr.: supernova thermonucléaire   

Same as → type Ia supernova

thermonuclear; → supernova.

tropical year
  سال ِ هورگردی   
sâl-e hurgardi

Fr.: année tropique   

The interval during which the Sun's mean longitude, referred to the mean equinox of date, increases by 360 degrees. Its mean length for the epoch J2000.0 is 365.24217879 real solar days (approximately 365.2422 days). This concept of tropical year, adopted by the International Astronomical Union at its General Assembly in Dublin, September 1955, has often been confounded with the → vernal-equinox year. In fact the mean period between two successive true vernal equinoxes is different from the tropical year. This period, which is equal to 365.24236460 solar days (about 365.2424 days), is the real mean length of the year in the Iranian calendar. The difference between the two year lengths is due to the fact that the Earth's orbital velocity around the Sun is not uniform, since the orbit is an ellipse. At the perihelion of its orbit the Earth is closest to the Sun, and therefore moves faster than average, while at aphelion, when it is farthest away from the Sun, it moves slower. Therefore the interval between two successive vernal equinoxes is not the same as the period between two successive summer solstices. In fact the tropical year does not depend on a specific origin for the annual apparent motion of the Sun. For detailed discussion see: A concise review of the Iranian calendar.

tropical; → year.

unclear
  نارونه   
nâruné

Fr.: non clair   

Difficult to see, hear, understand, or to be sure about.

un-; → clear.

vague year
  سال ِ گردان، ~ گرنگ   
sâl-e gardân, ~ gereng

Fr.: année vague   

A year of 365 days that overlooks the fraction of less than 0.25 days corresponding to the whole length of the → tropical year. The vague year was used in the → calendars of ancient Egypt, Iran, Mayas, and some other civilizations. Typically the vague year was divided into 12 months of 30 days each plus 5 → epagomenal days.

From annus vagus "wandering year;" → vagueyear.

vernal-equinox year
  سال ِ هموگان ِ بهاری   
sâl-e hamugân-e bahâri

Fr.: année d'équinoxe vernal, année vernale   

The time interval between two successive passages of the Sun, when the true longitude of the Sun is considered. In other words, the interval during which the Sun's true longitude increases by 360 degrees. Its mean length for the epoch J2000.0 is 365.24236460 real solar days (approximately 365.2424 days). The vernal-equinox year, on which the Iranian calender is based, should not be confused with → tropical year. See also: A concise review of the Iranian calendar. → Iranian calendar

vernal; → equinox; → year.

weak nuclear force
  نیروی ِ هسته‌ای ِ نزار، ~ ~ کمزور   
niru-ye hasteyi-ye nezâr, ~ ~ kamzur

Fr.: force nucléaire faible   

Same as → weak interaction.

weak; → nuclear; → force.

Wide Angle Search for Planets (WASP)
   WASP: جستجوی ِ سیاره با زاویه‌ی ِ گشاده   
WASP: josteju-ye sayâré bâ zâviye-ye gošâdé

Fr.: WASP: recherche à angle large de planètes   

An international collaboration, more accurately named SuperWASP, led by the United Kingdom, that aims at detecting → extrasolar planets by means of the → transit method. SuperWASP consists of two robotic observatories that operate continuously all year around, providing coverage of the sky in both hemispheres. The first, SuperWASP-North, is located on the island of La Palma. The second, SuperWASP-South, is located at the site of the South African Astronomical Observatory (SAAO). The observatories each consist of eight wide-angle cameras that simultaneously monitor the sky for → planetary transit events. Using the array of cameras makes it possible to monitor millions of stars simultaneously at an → apparent visual magnitude from about 7 to 13.

wide; → angle; → search; → planet.

year
  سال   
sâl (#)

Fr.: année, an   

In general, the time required for the Earth to complete one → revolution (approximately 3.154 × 107 seconds). Similarly, the time in which a planet completes its orbit around the Sun. In astronomy a distinction is made between various kinds of years, depending on the reference point used to measure the period of revolution: → anomalistic year; → Besselian year; → calendar year; → eclipse year; → embolismic year; → Galactic year; → Julian year; → leap year; → lunar year; → Platonic year; → sidereal year; → solar year; → Sothic year; → tropical year; → vernal-equinox year.

M.E. yeer; O.E. gēar (cf. O.S., O.H.G. jar, O.N. ar, Goth. jer, Du. jaar, Ger. Jahr); cf. O.Pers. dušiyāra- "evil year, bad harvest, famine" (from duš- "bad," → dys-, + yār- "year"); Av. yārə- "year;" Skt. paryārini- (*pari-yāram "a year long") "cow which has its first calf after a year;" Gk. hora "season, time of a day, year;" L. hornus "of this year;" → hour.

Sâl "year;" Mid.Pers. sâl "year;" Sogd. sarδ "year;" O.Pers. θrad- "year;" Av. sarəd- "year;" cf. Skt. śarád- "autumn;" maybe related to Lith. šilti "to become warm;" L. calor "heat," calere "to become warm;" PIE base *kele- "warm."


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