Understanding Black Hole Mass
Black holes are among the most fascinating and extreme objects in the universe. Their mass determines the size of their event horizon—the point of no return where even light cannot escape the gravitational pull.
The Formula
The relationship between a black hole's mass and its event horizon radius can be expressed as:
[\text{Black Hole Mass} = \frac{\text{Radius of Event Horizon}}{3}]
Where the radius is measured in kilometers and the mass is expressed in solar mass units (the mass of our Sun).
This simplified formula is derived from the Schwarzschild radius equation, which relates a non-rotating black hole's mass to the radius of its event horizon.
Example Calculation
Let's calculate the mass of a black hole with an event horizon radius of 9,000,000 km:
- Start with the radius: 9,000,000 km
- Divide by 3: 9,000,000 ÷ 3 = 3,000,000
- Result: 3,000,000 solar mass units
This means the black hole is approximately 3 million times more massive than our Sun—similar to the supermassive black hole at the center of the Milky Way galaxy.
Black Hole Categories
Based on mass calculations, black holes are classified into several categories:
- Stellar-mass black holes: 3 to 100 solar masses, formed from collapsed stars
- Intermediate-mass black holes: 100 to 100,000 solar masses
- Supermassive black holes: Millions to billions of solar masses, found at galaxy centers
- Primordial black holes: Hypothetical black holes of any mass formed in the early universe
Understanding black hole mass helps astronomers study galaxy formation, gravitational waves, and the fundamental nature of spacetime.