Artist's impression of the Galactic Centre
This illustration shows an artist's impression of the environment at the centre of our Galaxy, the Milky Way. The Galactic Centre hosts a supermassive black hole in the region known as Sagittarius A*, or Sgr A*. With the mass of about 4 million times that of our Sun, this black hole currently accretes matter from its surroundings at very moderate rates compared to the vigorous processes that characterise black-hole accretion in galaxies hosting an Active Galactic Nucleus (AGN).
A dense torus of molecular gas and dust, the circumnuclear disc, surrounds the Galactic Centre and occupies the innermost 15 light-years of the Galaxy. Enshrouded within the disc is a central cavity, with a radius of a few light-years, filled with warm dust and lower density gas. Part of this gas is being ionised by the strong ultraviolet radiation from massive stars that closely orbit the central black hole.