What is the physical size of a 1-billion-solar-mass black hole compared to the Sun?

Dimensions and Definition of Supermassive Black Holes

Astronomy enthusiasts often wonder about the actual physical dimensions of supermassive black holes, which are among the most mysterious structures in the universe. Joseph De Benedetto raised a fundamental question regarding how a supermassive black hole measured at 1 billion solar masses compares in physical size to our Sun.

The Event Horizon and Mathematical Boundaries

When evaluating the physical size of a black hole, astronomers look directly at its event horizon rather than a solid surface. The event horizon is a mathematical boundary determining the point of no escape for light and matter, calculated proportionally to the black hole's mass.

Comparison with the Sun and Physical Scale

The physical scale of systems reaching 1 billion solar masses expands to sizes comparable to our Solar System. The radius of the event horizon grows proportionally with mass, providing foundational metrics to help comprehend these massive cosmic entities.