https://science.sciencemag.org/content/300/5627/1898

"Black hole horizons are among the most comprehensively understood phenomena predicted by theory [see (

*) for a nontechnical introduction to the theoretical properties of black holes; see (*

**1***) for an undergraduate-level presentation of mathematical aspects of black hole physics].*

**2**One aspect of this simplicity is the fact that any black hole can be characterized by its mass, angular momentum, and electric (or certain other types of quantum) charge. Charge may not be important in an astrophysical setting, so black holes effectively can be described by two parameters. Far from the horizon, black holes exert a gravitational influence just like any spherical body of the same mass. If the Sun collapsed symmetrically and became a black hole, there would be no change in Earth's orbit. Black holes have been discovered primarily by measuring their gravitational effects on distant bodies."