An active semiconductor device with a small low-powered solid-state electronic device consisting of a semiconductor and three or more electrodes, used as an amplifier and rectifier and frequently incorporated into integrated circuit chips. Although much smaller in size than a vacuum tube, it performs similar functions without requiring current to heat a cathode.
1) An event where one astronomical object appears to move across the
face of another. As seen from Earth, the planets Venus and Mercury are
seen to transit the Sun. We can also observe natural satellites transit the
face of their host planet. Similarly exoplanets have been observed to transit their
host stars. See also → planetary transit,
→ transit method.
M.E., from L. transitus, p.p. of transire "to go or cross over," from → trans- "across" + ire "to go."
Gozar "passage, transit, passing," from gozaštan "to pass, cross, transit," variant gozâštan "to put, to place, let, allow;" Mid.Pers. widardan, widâštan "to pass, to let pass (by);" O.Pers. vitar- "to pass across," viyatarayam "I put across;" Av. vi-tar- "to pass across," from vi- "apart, away from" (O.Pers. viy- "apart, away;" Av. vi- "apart, away;" cf. Skt. vi- "apart, asunder, away, out;" L. vitare "to avoid, turn aside") + O.Pers./Av. tar- "to cross over;" → trans-.
parhun-e gozar, ~ nimruzâni
Fr.: cercle méridien
An observing instrument provided with a graduated vertical scale, used to measure the declinations of heavenly bodies and to determine the time of meridian transits. Same as → meridian circle.
sâzâl-e gozare nimruzâni
Fr.: instrument méridien
An instrument mounted so as to allow it to be pointed only at objects in the sky crossing the local meridian. Also known as → transit telescope.
Fr.: méthode du transit
A method for detecting → exoplanets that is based on the decrease of star → brightness when the exoplanet passes in front of its star. As the planet transits, a portion of the light from the star is blocked causing a decrease in the → magnitude of the star. The amount of decrease (typically between 0.01% and 1%) depends on the sizes of the star and the planet. The duration of the transit depends on the planet's distance from the star and the star's mass. This change must be periodic if it is caused by a planet. In addition, all transits produced by the same planet must be of the same change in brightness and last the same amount of time. Once detected, the planet's distance from its star can be calculated from the period and the mass of the star using → Kepler's third law of planetary motion. The size of the planet is found from the depth of the transit and the size of the star. From the orbital size and the temperature of the star, the planet's characteristic temperature can be calculated. Knowing the star's mass and size, the planet's size and distance can be estimated. Also the composition of a → transiting planet's atmosphere can, in principle, be determined.
transit of Mercury
Fr.: transit de Mercure
The crossing the face of the Sun by the planet Mercury, as seen from Earth. Because the plane of Mercury's orbit is not exactly coincident with the plane of Earth's orbit, Mercury usually appears to pass over or under the Sun. On the average it occurs 13 times each century when the Earth is near the → line of nodes of Mercury's orbit. The three last transits were on 2003 May 07, 2006 November 08, and 2016 May 09. The next one will be on 2019 November 11. The first observation of a transit of Mercury was on November 7, 1631 by Pierre Gassendi. On June 4, 2014 NASA's Mars rover Curiosity photographed a transit of Mercury, marking the first time such a phenomenon has ever been imaged from the surface of a planet other than Earth. See also → black drop.
transit of Venus
Fr.: transit de Vénus
A rare phenomenon that happens when the planet Venus passes directly between the Sun and Earth and is therefore seen against the solar disk. Such a passage occurs every 122 or 105 years and when it happens the next occurrence is after 8 years. Only seven transits of Venus have occurred since the invention of the telescope: in 1639, 1761, 1769, 1874, 1882, 2004, and 2012. The next one will be in 2117. The reason for this rarity is that the Earth and Venus do not orbit the Sun in the same plane. Their orbital planes have a relative inclination of about 3°. The first observation of the Venus transit was in 1639 by the English Jeremiah Horrocks (1618-1641). See also → black drop.
durbin-e gozar-e nimruzâni, teleskop-e ~ ~
Fr.: lunette méridienne
Same as → transit instrument.
Fr.: temps de passage
The time interval between the release of an electron at the photocathode and the arrival of an electron at the anode. Transit time is not a single-valued quantity, but has a bell-shaped distribution.
sayyâre-ye dar gozar
Fr.: planète en transit
TRAnsiting Planets and PlanetesImals Small Telescope (TRAPPIST)
A Belgian facility devoted to the detection and characterization of → exoplanets and to the study of → comets (→ transiting planet) and other → small solar system bodies. It consists of two 60 cm robotic telescopes located at the → European Southern Observatory, → La Silla, in Chile and at Oukaïmden Observatory in Marroco.
1) Passage from one position, state, stage, subject, concept, etc., to another.
From L. transitionem (nominative transition) "a going across or over," noun of action from transire "go or cross over," from → trans- "across" + ire "to go."
gerde-ye gozaresh, disk-e ~
Fr.: disque de transition
The → accretion disk of a → T Tauri star that displays very weak or no → infrared excess at → near infrared wavelengths, but shows strong excess at → intermediate infrared and longer wavelengths. This happens when the hot inner dust disk has dissipated whereas the cooler outer disk is still intact.
Fr.: fonction de transition
Fr.: probabilité de transition
The probability that a quantum-mechanical system will make a transition from a given initial state to a given final state.
Fr.: flux de transition
1) tarâjâyidan; 2) tarâzabânidan
Fr.: 1) translater; 2) traduire
1a) Mechanics: To subject a body to → translation.
M.E. translaten, from L. translatus, from → trans- "across" + latus suppletive p.p. of ferre "to carry;" cognate with Pers. bordan "to carry, transport;" Mid.Pers. burdan; O.Pers./Av. bar- "to bear, carry," barəθre "to bear (infinitive);" Skt. bharati "he carries;" Gk. pherein "to carry;" PIE base *bher- "to carry."
1) Tarâjâyidan, from tarâ-, → trans- "across" +
jâ "place" (from Mid.Pers. giyag "place;" O.Pers. ā-vahana-
"place, village;" Av. vah- "to dwell, stay," vanhaiti "he dwells, stays;"
Skt. vásati "he dwells;" Gk. aesa (nukta) "to pass (the night);"
Ossetic wat "room; bed; place;" Tokharian B wäs- "to stay, wait;"
PIE base *ues- "to stay, live, spend the night")
+ -idan infinitive suffix.
1, 2) tarâjâyeš; 3) tarâzabâneš
1) Mechanics: A motion of a rigid body characterized by parallel paths of all
particles. Every point of the body in translation has the same
velocity and acceleration at any particular instant. The translation motion
may be rectilinear or curvilinear.
Verbal noun of → translate.
Tarâjâyeš, verbal noun of tarâjâyidan, tarâzabâneš, verbal noun of tarâzabânidan, → translate.
The quality of a material that allows light to pass through, but only diffusely, so that objects on the other side cannot be clearly distinguished. → transparent.
From L. translucent-, p.p. of translucere "to shine through," from → trans- + lucere "to shine," related to lux "light," lucidus "clear," luna, "moon;" Fr. lumière "light;" cf. Pers. ruz "day," rowšan "bright, clear," rowzan "window, aperture;" foruq "light," afruxtan "to light, kindle;" Mid.Pers. rôšn "light; bright, luminous," rôc "day;" O.Pers. raucah-rocânak "window;" O.Pers. raocah- "light, luminous; daylight;" Av. raocana- "bright, shining, radiant;" akin to Skt. rocaná- "bright, shining," roka- "brightness, light;" Gk. leukos "white, clear;" O.E. leoht, leht, from W.Gmc. *leukhtam (cf. O.Fris. liacht, M.Du. lucht, Ger. Licht), from PIE *leuk- "light, brightness."
Tarâtâb, from tarâ-, → trans- + tâb present stem of tâbidan "to shine," variants tâftan "to shine," tafsidan "to become hot;" Mid.Pers. tâftan "to heat, burn, shine;" taftan "to become hot;" Parthian t'b "to shine;" Av. tāp-, taf- "to warm up, heat," tafsat "became hot," tāpaiieiti "to create warmth;" cf. Skt. tap- "to heat, be/become hot; to spoil, injure, damage; to suffer," tapati "burns;" L. tepere "to be warm," tepidus "warm;" PIE base *tep- "to be warm."
Fr.: nuage translucide
A type of → interstellar medium cloud where → carbon (C), in → ionized atomic form and protected from → interstellar radiation, transforms into neutral atomic or molecular form. The chemistry in this regime is qualitatively different than in the → diffuse molecular clouds, both because of the decreasing electron fraction and because of the abundance of the highly reactive C atoms. The translucent cloud regime is the least well understood of all the cloud types. This is partly because of a relative lack of observational data, but also because theoretical models do not all agree on the chemical behavior in this transition region. In some models, there is a zone where the abundance of C exceeds that of C+ and CO; in others the peak abundance of C falls below that of C+ and CO. To cope with this uncertainty, Snow & McCall (2006) propose a working definition of translucent cloud material as gas with C+ fraction < 0.5 and CO fraction < 0.9. This definition reflects the fact that C+ is no longer the dominant form of carbon as it converts to neutral or molecular form, but also excludes the → dense molecular clouds, where carbon is almost exclusively CO (Snow & McCall, 2006, ARA&A 44, 367).