The center of our Milky Way galaxy lies about 27000 light-years absent in the direction of the constellation of Sagittarius. At its core is a black hole about four million solar masses in size. Around the black hole is a donut-shaped structure about eight light-years across that rings the inner volume of neutral gas and thousands of individual stars. Around that,stretching out to about 700 light-years, is a dense zone of activity called the Central Molecular Zone (CMZ). It contains nearly eighty percent of all the dense gas in the galaxy - a reservoir of tens of millions of solar masses of fabric - and hosts giant molecular clouds and massive star forming clusters of luminous stars, or among other regions many of which are poorly understood.
Source: phys.org