Yes, there is a massive black hole at the centre of the galaxy. The universe comprises Galaxies that are huge congregation of stars held together by the forces of gravity and dark energy from dark matter. Stars account for most of the visible galactic matter and mass. Black holes result from the collapse and compaction under gravity of a star of mass greater than three times that of the Sun at the end of its life cycle. Its density becomes so great that nothing, not even its light, can escape from its gravity. It is called a black because it cannot be viewed directly since no light emits from it.