Black holes come in many different sizes. Theoretically, black holes can be formed through the crushing of any matter into a small enough space. If the Sun was crushed to a diameter of 1.9 miles, the Earth crushed to the size of a peanut, or a human crushed to 1 billionth of a meter (nanometer), a black hole would form. However, these black holes cannot form naturally. The smallest known black hole has 3.8x the mass of our Sun and is 15 miles in diameter.
The largest black holes are found in the center of galaxies, formed billions of years ago, these monstrosities are called "Supermassive Black Holes", of SMBH for short. Although theroies exist as to how black holes of these sizes exist, it's still an open question that researchers are pursuing today. The SMBH at the center of the Milky Way is Sagittarius A. With a mass that's over 4 million times the mass of our Sun, Sagittarius A has a diameter of over 54 million miles. However, Sagittarius A pales in comparison to the Supermassive Black Hole NGC 4889, which has a mass equal to 37 billion suns. Making up 14% of its host galaxy's mass,(an average black hole represents 0.1% of its galaxy's mass), the black hole has a diameter of more than 80 billion miles - more than 15x the diameter of Neptune's orbit around the sun.
| Name | Size (In Solar Masses) |
|---|---|
| Ton 618 | 6.6x10^10 |
| S5 0014+81 | 4x10^10 |
| SDSS J102325.31+514251.0 | 3.31x10^10 |
| H1821+643 | 3x10^10 |