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MASS EFFECT QUASAR HOW TO

In addition to black holes and accretion disks, quasars have other remarkable features. (The Sun’s luminosity is about 4 × 10 26 watts.) What distinguishes an “active” galactic nucleus from other galactic nuclei (the 90–95 percent of large galaxies that are currently not quasars) is that the black hole in an active nucleus accretes a few solar masses of matter per year, which, if it is accreting at around 1 percent or more of the Eddington rate, is sufficient to account for a typical quasar with a total luminosity of about 10 39 watts. There is a maximum rate set by the Eddington limit at which a black hole can accrete matter before the heating of the infalling gas results in so much outward pressure from radiation that the accretion stops. In about 5–10 percent of these galaxies, gas tumbles into the deep gravitational well of the black hole and is heated to incandescence as the gas particles pick up speed and pile up in a rapidly rotating “ accretion disk” close to the horizon of the black hole. Supermassive black holes reside at the centres of many large galaxies. Quasars and other AGNs are apparently powered by gravitational accretion onto supermassive black holes, where “supermassive” means from roughly a million to a few billion times the mass of the Sun. Quasar and its companion galaxy colliding Quasars have also been discovered through other techniques, including searches for starlike sources whose brightness varies irregularly and X-ray surveys from space indeed, a high level of X-ray emission is regarded by astronomers as a sure indicator of an accreting black-hole system. This remains the primary technique for finding quasars, although it has evolved over the years with the replacement of film by electronic charge-coupled devices ( CCDs), the extension of the surveys to longer wavelengths in the infrared, and the addition of multiple filters that, in various combinations, are effective at isolating quasars at different redshifts. The photographs are then compared to locate the unusually blue objects, whose nature is verified through subsequent spectroscopy. This can be done with relatively high efficiency by photographing large areas of the sky through two or three different-coloured filters.

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MASS EFFECT QUASAR HOW TO

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