What are quasars?

Scritto da:MD     Categoria: Atronomia

Quasar

Da Wikipedia, the free encyclopedia:  http://it.wikipedia.org/wiki/Quasar

Un quasar (contracted of quasi-stellar radio source, almost stellar radio source) is an astronomical object that looks like a star in an optical telescope (ie a point source) and that shows a large red shift (redshift) del suo spettro. The general consensus is that this large redshift is of cosmological origin, that is the result of Hubble’s law. This implies that quasars are very distant objects and should emit more energy than dozens of normal galaxies. In fact, quasars are considered the brightest objects in the observable Universe and one of their characteristics is to emit the same amount of radiation in almost the whole electromagnetic spectrum, from radio waves to X-rays and gamma.

Some quasars show rapid changes of their brightness, which implies that they are very small (an object can not change brightness faster than the time it takes light to pass through it). If the cosmological interpretation is correct, the enormous brightness and the sudden flare-ups of a quasar are totally unimaginable to the human mind: a quasar medium can incinerate the entire planet Earth from many light-years away and emit so much energy in one second how much the Sun emits a hundred thousand years.

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