school energy&environment

Quasar

The Quasars (Quasi-stellar Radio Source) are really far galaxies, the furthest we saw, able to emit an enormous quantity of energy, above all on the radio frequencies.
Looking with a telescope, they appear like bright dots, with a stellar aspect (from which it derives the definition, Quasi-stellar Radio Sources), while their spectrum shows bands considerably inclined to the red color (redshift).
If we suppose that this redshift is due to the Doppler effect, this would mean that these objects are coming away from us with high speeds, superior than 35000 km/s, too elevated for a normal star. In conclusion, we are talking about really far extragalactic sources.
Considering their distance and their apparent brightness, we can also find the enormous power radiated by these objects, hundreds times more than the most sparkling galaxies.
The engine of these quasars is not the nuclear reactions inside the single stars: the power we observed is not the addition of the energy contribution of all the stars of this galaxy. Scientists are almost sure that this powerful engine is powered by a giant black hole placed in the galactic nucleus. Around this black hole there is an accretin disc of gas and stars in extremely quick rotation. The matter, falling on this black hole, creates an enormous power of radiation.