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active galactic nucleus |
Also found in: Dictionary/thesaurus, Wikipedia, Hutchinson | 0.06 sec. |
active galactic nucleusSmall region at the centre of a galaxy that emits a prodigious amount of energy in the form of radio, optical, X-ray, or gamma radiation or high-speed particle jets. Many classes of “active galaxies” have been identified; they appear similar in many respects to quasars. Astronomers suspect that the observed energy is generated as matter accretes onto a supermassive black hole with a mass millions or even billions of times that of the Sun. The accreting matter can outshine the rest of the galaxy as it is heated in very high-speed collisions outside the black hole's event horizon. It is believed that many galaxies harbour these central black holes and that they might have been quasars in their early history, although they now appear to be dormant unless orbiting matter is accreting onto the black hole. How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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The investigators hope to
detect high-energy neutrinos released in astrophysical events such as
the cataclysmic gravitational collapse of a star or the accretion of
matter in the massive core of an active galaxy. And when
the galaxy is the nearest active galaxy to us, Centaurus A, which also
happens to be one of the strongest and longest studied celestial sources
of radio waves, the combination provides a rather unique excitement for
astronomers. |
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