A black hole collision releases roughly
Joules. For a split second, it radiates 50 times more power than all stars in the observable universe combined—yet emits no light.
Instead, it generates pure energy in the form of gravitational waves: ripples in the fabric of spacetime itself.
When two black holes spiral inward and finally merge, a significant portion of their combined mass is converted directly into energy according to Einstein's . The first gravitational wave event ever detected, GW150914, involved the collision of two black holes with masses roughly 36 and 29 times that of our Sun. They merged into a single black hole weighing 62 solar masses.
The missing three solar masses were converted entirely into gravitational wave energy in a fraction of a second.
Here is how that Joules figure is calculated:
- One solar mass is about kilograms.
- The three missing solar masses equal roughly kilograms.
- Multiplying that mass by the speed of light squared () gives the total energy output.
To put this number in context, a typical supernova releases around Joules over several weeks. Our Sun, burning steadily for its entire 10-billion-year lifespan, will produce roughly Joules from start to finish.
The collision of those two black holes released about 4,500 times more energy than the Sun will generate in its entire existence.
Because this energy was unleashed in just two-tenths of a second, the peak power output was immense.
Yet, because gravitational waves interact so weakly with matter, by the time this wave reached Earth 1.3 billion years later, it merely stretched the four-kilometer arms of the LIGO detectors by a distance a thousand times smaller than the width of a proton.