quasar


quasar
/kway"zahr, -zeuhr, -sahr, -seuhr/, n. Astron.
one of over a thousand known extragalactic objects, starlike in appearance and having spectra with characteristically large redshifts, that are thought to be the most distant and most luminous objects in the universe. Also called quasi-stellar object.
[1960-65; quas(i-stell)ar, in QUASI-STELLAR RADIO SOURCE, the first type of quasar discovered]

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Any of a class of enigmatic cosmic objects of high luminosity and strong radio emission observed at extremely great distances; also, a closely related object that has the same optical appearance but does not emit radio waves, i.

e., a so-called quasi-stellar object (QSO). Most quasars exhibit very large redshifts, suggesting that they are moving away from Earth at tremendous speeds (approaching the speed of light); they thus are some of the most distant known objects in the universe. Quasars are no more than a light-year or two across but as much as 1,000 times more luminous than a giant galaxy having a diameter of 100,000 light-years; their extreme brightness allows them to be observed at distances of more than 10 billion light-years. Many investigators attribute such energy generation to matter spiraling at high velocity into a supermassive black hole (millions or billions of times as much mass as the Sun) at the centre of a distant galaxy. See also active galactic nucleus.

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 any of a class of rare cosmic objects of high luminosity that often have strong radio emission that is observed at great distances. These objects are also called QSOs, which stands for “quasi-stellar objects.”

      The bright emitting regions of quasars are no more than a light-year or two in size, but they are up to 1,000 times more luminous than giant galaxies (galaxy), which can have a diameter of 100,000 light-years. The tremendous brilliance of quasars allows them to be observed at distances of more than 10,000,000,000 light-years. This enormous amount of radiation is released from a small area at the centre of what appears to be a normal galaxy. Some evidence suggests that the galaxy is experiencing a tidal encounter with another galaxy. Most investigators attribute such energy generation to gas spiraling at high velocity into a massive black hole. An outer atmosphere of tenuous gas produces emission lines that are observed in the spectra (spectrum) of quasars. These emission lines are always shifted toward the red, corresponding to large Doppler (Doppler, Christian) velocities of recession. According to Hubble's law (Hubble's constant) of the expansion of the universe, these large velocities correspond to large distances. Quasars were more numerous about 10 billion years ago than they are at present. The brightest quasar in the sky is 3C 273, which lies at a distance of 2,000,000,000 light-years from the Earth. Radio interferometry shows that the radio nucleus of 3C 273 is emitting jets of ionized gas that are expanding at nearly the velocity of light.

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Universalium. 2010.

Look at other dictionaries:

  • quasar — QUASÁR, quasari, s.m. (astron.) Obiect cosmic, cu strălucire de zeci sau sute de ori mai puternică decât a celor mai mari galaxii, care emite intens radiounde. [pr.: cua . – abr.: QSR] – Din engl., fr. quasar. Trimis de cata, 24.02.2002. Sursa:… …   Dicționar Român

  • quasar — [ kazar ] n. m. • 1965; mot angl. 1964, abrév. de quasi stellar radio source « source d émission radio quasi stellaire » ♦ Astron. Astre d apparence stellaire, source d ondes hertziennes (radiosource) dont l émission est supérieure à celle d une… …   Encyclopédie Universelle

  • quásar — Voz tomada del acrónimo inglés quasar (de quas[i stell]ar [radio source]), que designa un cuerpo celeste de pequeño tamaño y gran luminosidad. En español debe escribirse con tilde por ser voz llana acabada en consonante distinta de n o s (→… …   Diccionario panhispánico de dudas

  • quasar — |quà| s. m. Fonte de rádio de grande potência que corresponde geralmente a um objeto luminoso de fraquíssima dimensão angular e reconhecível nos negativos fotográficos. (A natureza dos quasares é ainda objeto de controvérsias.) • Plural: quasares …   Dicionário da Língua Portuguesa

  • quasar — (n.) 1964, from quas(i stell)ar radio source (1963) …   Etymology dictionary

  • quasar — (Voz ingl.), acrón. de quasi stellar [radio source]). m. Astr. Cuerpo celeste de pequeño diámetro y gran luminosidad, que emite grandes cantidades de radiación en todas las frecuencias. Es el tipo de astro más alejado en el universo …   Diccionario de la lengua española

  • quasar — ► NOUN ▪ a massive and extremely remote celestial object which emits large amounts of energy. ORIGIN contraction of quasi stellar radio source: telescope images of quasars are typically star like …   English terms dictionary

  • quasar — ☆ quasar [kwā′zär΄, kwā′sär΄ ] n. [< quas(i stell)ar (radio source)] any of a number of starlike celestial objects that emit immense amounts of light and, often, radio waves, characterized by having spectral lines with very large redshifts:… …   English World dictionary

  • Quasar — This article is about the astronomical object. For other uses, see Quasar (disambiguation). Artist s rendering of ULAS J1120+0641, a very distant quasar powered by a black hole with a mass two billion times that of the Sun[1]. Credit: ESO/M.… …   Wikipedia

  • Quasar — Pour les articles homonymes, voir Quasar (homonymie). Vue d artiste du quasar GB1508 Un Quasar, « source de rayonnement quasi stellaire », (quasi stellar radio source en …   Wikipédia en Français

  • Quasar — Künstlerische Darstellung eines Quasars Ein Quasar ist der Kern einer aktiven Galaxie, die im sichtbaren Bereich des Lichtes nahezu punktförmig (wie ein Stern) erscheint und ungeheure Energiemengen in anderen Wellenlängenbereichen ausstrahlt. Auf …   Deutsch Wikipedia


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