This picture shows our view in the direction of the constellations Sagittarius, in the direction of the central core of our Galaxy. Our view of the Galactic Center is hidden by gas, dust and tightly packed stars. If you were to fly off in this direction at the speed of light, in 30 thousand years you would arrive at the central hub of the Milky Way. Since a trip isn't exactly practical, how can we know if a black hole lurks there if we can't see the center?

\
Galactic Center

+

Our Galaxy, The Milky Way