Sagittarius A*—pronounced Sagittarius A star—is the supermassive black hole at the center of the Milky Way galaxy, our galactic home. It is a huge source of radio emissions and may be the reason our galaxy exists in the form it does. The unique characteristic of a supermassive black hole is its density. Versus a stellar black hole (one formed directly from the collapse of a star), a supermassive black hole has the density of water (its huge mass divided by a larger volume=a small density) and thus the forces at the event horizon would be minimal. This novel physical property is used by Lauren in A Quantum Singularity as a sling-shot to move across the Milky Way galaxy.