Galaxy. Ambartsumian puts forward an entirely new concept, that the light absorption in the Galaxy is caused by the presence of numerous dust nebulae or "absorbing clouds" in the inter-stellar space. Based on this concept of patchy structure of the inter-stellar absorbing matter the fluctuation theory was developed, which became a new direction in the astronomy.

Ambartsumian's marvelously elegant formulation of the fluctuations in brightness in the Milky Way: in the limit of infinite optical depth, the probability distribution of the fluctuations in the brightness of the Milky Way is invariant to the location of the observer. In the related series of investigations, in part in association with Academician Markarian, Ambartsumian introduced for the first time the now commonly accepted notion that interstellar matter occurs in the form ofearly 1950s when Ambartsumian first raised the issue of the active galactic nuclei (AGN). In his famous report at the Solvay Conference on Physics (Brussels, 1958) Ambartsumian said that enormous explosions take place in galactic nuclei and as a result a huge amount of mass is expelled. In addition, if this was so, these galactic nuclei must contain bodies of a huge mass and unknown nature. During a break in the session Walter Baade went up to Ambartsumian and said, "Professor Ambartsumian, you have come from the Soviet Union, and I from America. Logically speaking, you should be a materialist, and I an idealist. But what you have just said is nothing other than a pure idealism! It's fantastic! You speak about some kind of 'non-stellar' objects which