The supermassive black hole V616 Monocerotis is the closest to our Earth at a distance of just 3,300 light-years away. Supermassive black holes like V616 are monstrous wells of gravity, typically found at the dead centre of galaxies. But there could be another, secretly hidden black hole somewhere much closer to our home planet if two Japanese astrophysicists are correct. According to astronomers Daichi Tsuna and Norita Kawasaki from the University of Tokyo, past studies show there could be up to 100 million black holes hiding throughout the Milky Way.