Final answer:
The classifications of astrophysical black holes are primordial, stellar, intermediate, and supermassive. These classifications vary based on their mass and formation processes, ranging from small hypothetical primordial black holes to the massive supermassive black holes at the centers of galaxies.
Step-by-step explanation:
The size classifications of astrophysical black holes are named: primordial, stellar, intermediate, and supermassive. These classes are distinguished by their masses and the physical processes from which they may form. Primordial black holes are hypothetical and would be very small; they may have formed right after the Big Bang.
Stellar black holes result from the collapse of massive stars and have masses typically ranging from a few solar masses to tens of solar masses. Intermediate black holes are a mystery in terms of their formation and range from hundreds to thousands of solar masses. Supermassive black holes are found at the centers of galaxies and range anywhere from millions to billions of solar masses.
For example, the black hole at the center of the Milky Way is a supermassive black hole with a mass equivalent to 4.6 million Suns, fitting within a sphere smaller than Mercury's orbit. The event horizon's radius of a black hole corresponds to its mass, with more massive black holes having larger radii.