The biggest known black hole, TON 618, is thought to contain 66 billion solar masses — that’s two-thirds the mass of the entire Milky Way! In size, its diameter is 2600 AU, or 390 billion km — more than 40 times the diameter of Neptune’s orbit. If TON 618 were the size of the Earth, the Earth would be a 41.6 cm ball next to it, about the size of a typical house globe.
Keishinrei 