Why could the concentration of matter at the center of an active galaxy like M87 not be made of stars?

an active galaxy is the galaxy that produces large amounts of energy in a very small volume of space.

Explanation:

active galaxies such as the M87 gives out extremely bright straight jets having speeds close to the speed of light providing the evidence that power in active galaxies is concentrated in a small region. this power from such a small region cannot be generated throught nuclear fusion as it happens in stars, this is the region why the concentration of matter in the center of this galaxies is not made up of stars.