The radiation of a quasar (quasi-star radio source) is equal to the radiation of hundreds of galaxies taken together. And nevertheless they look like stars. Why is such an energy emitted in a small volume? This is the main mystery of quasars. It isn’t revealed even by now.

  The history of the discovery of quasars worth attention. At the first years of the development of radio astronomy the accuracy of positions of discovered sources was not enough to make optical identifications. So the astronomers suggested an original way to determine the coordinates of some radio sources. Sometimes the Moon in its movement covers a source. Since the position of the Moon is known very precisely, it is only necessary to fix the time when the Moon covers the source.

  In 1963 the Moon was to cover a very bright radio source 3C 273. The observations passed successfully, and the 3C 273 was identified with a star of 13-th star value. It’s a bright star for the astronomers. The optical spectrum of this star was absolutely unlike to any spectrum class. The lines of this spectrum were strongly moved to the red area, which means that 3C 273 moves away with of speed of 50 000 km/s, and is about 1 milliard light years away.

  There are a thousands of quasars discovered by now. Most of them are the most powerful radio sources and are located about 10-15 milliard light years away, in other words, almost on the border of the observed Universe.

  So, these objects look like stars, are located at huge distances, and emit the power hundreds times more than the whole galaxies. Quasars’ power radiation exceeds the Sun’s one thousand of milliard times!

  By their observed properties quasars look like the active cores of galaxies with the difference that the level of their activity is much higher. There appeared a supposition that quasars are the cores of galaxies at the stage of extreme activity when the optical emission of the core covers the emission of the galaxy. And really there was discovered a weak luminescence around the closest quasars which can belong to the star system. Sometimes even some details of galaxies can be seen.