What Happens When Two Black Holes Collide?! | How the Universe Works | Science Channel

Added: 2026-05-30

[00:00:00]We're taking our seats for the most violent event in the universe, the collision of two super massive black holes. We've never witnessed this cosmic heavyweight championship, but we can build up a picture of this epic fight by studying other weight classes with lighter fighters.

[00:00:23]2020, the Earthbound Gravitational Wave Detector, LIGO, picks up the distinctive signal of a stellar mass black hole merger.

[00:00:34]What we saw was a black hole of 85 times the mass of our sun and another black hole of 66 times the mass of our sun smashing together to create a combined black hole.

[00:00:48]As someone who studies black hole mergers, this was a really exciting event.

[00:00:53]>> We're talking about the largest, the heaviest, the most massive black holes we have seen collide to date.

[00:01:01]It may be the largest detection, but on a universal scale, it's still a small fry. Like lightweight boxers, the two black holes circle each other and emit low energy gravitational waves.

[00:01:16]This energy loss causes the black holes to spiral in together.

[00:01:21]Finally, they collide in a cosmos shattering event, forming a single black hole and releasing a huge blast of gravitational waves. But when astronomers examine the single merged black hole, something doesn't add up.

[00:01:40]>> If you take the combined mass of the two black holes, you get to 150 times the mass of our sun. But actually, the black hole that's left only has a mass of 142 times the mass of our sun. So, the mass you have before the event does not equal the mass you have after the event. What happened to that missing eight solar masses? The way these black hole mergers work is very roughly 5% of the total mass of the system gets converted into energy.

[00:02:15]It all comes down to E= MC^2.

[00:02:20]>> This is that beautiful equation that Einstein told us. E= MC². E is the energy and M is the mass.

[00:02:28]>> Einstein taught us that mass and energy are related. In fact, much of what we call mass is actually energy. In this case, the violence of the collision transforms 18,000 trillion trillion tons of matter into an explosion of gravitational waves.

[00:02:48]>> In just a fraction of a second, 8 suns worth of matter is converted into pure unadulterated energy. The amount of energy released was so great that if you add up all the energy of all the stars burning in the universe, it was bigger than that.

[00:03:08]>> This event was a collision between relative lightweights, two stellar mass black holes.

[00:03:18]To understand heavyweight bouts, we need to scale up to super massive black holes.

[00:03:28]In the universe of sports, super massive black holes are the heavyweight contenders.

[00:03:33]>> With these big black holes, size matters. The bigger the better.

[00:03:38]>> More mass means more energy, which means more destructive power.

[00:03:43]>> We don't need to look too far to find this devastating muscle. This is M87 star, one of the largest super massive black holes in our cosmic zip code.

[00:03:57]M87 star is huge. It weighs about 6 billion solar masses, about 6 billion suns, and it's the size of our solar system.

[00:04:07]>> A collision between two 6 billion solar mass super massive black holes would release around 5 * 10 to the power of 56 jewels.

[00:04:17]So, what's that mean in real world terms?

[00:04:21]>> It's hard to use words to express how much energy this is. And the numbers are so huge they're almost meaningless. The only way I can really explain this is in physics we have these comparisons so we can get a mental picture. But for something like this there is no mental picture that is so freaking big.

[00:04:46]>> So where does this destructive mass and energy come from?

[00:04:54]It starts with the simplest ingredient, hydrogen.

[00:05:01]Hydrogen is the basic building block of the universe.

[00:05:06]Each atom is tiny, but it contains a lot of energy.

[00:05:11]>> Hydrogen atoms contain a huge amount of energy, just like all matter does. And if it's unlocked in a certain way, there can be huge explosions.

[00:05:23]I mean, you take the mass contained simply in my hand and you could blow up pretty much the entire Earth.

[00:05:29]>> Matter has energy because it formed from energy in the early moments of the universe.

[00:05:36]>> In many ways, atoms are reservoirs of stored energy from the Big Bang.

[00:05:43]>> 13.8 8 billion years ago, the universe ignites at a super hot ball of intense energy.

[00:05:53]Right after the Big Bang, there's a tremendous amount of energy. So much energy, in fact, that normal atoms can't exist.

[00:06:01]>> As that early energy starts to cool, it can start to form primitive matter.

[00:06:09]The universe takes that first matter and energy in the form of hydrogen atoms and starts the process of creating a super massive black hole. Step one, build giant stars.

[00:06:24]>> So, gravity brings together gas, dust, hydrogen, all of that stuff. And as the clouds become more dense, they attract even more material.

[00:06:34]>> As they spin, they get hotter and hotter. And as that temperature and pressure increase, finally it ignites nuclear fusion within the core and creates an actual star.

[00:06:48]These huge stars are like cosmic rock stars. They live fast and die young.

[00:06:55]When they die, they flame out in a huge explosion, a supernova.

[00:07:02]The entire star turns itself inside out and releases a shock wave going a good fraction of the speed of light and releases enough energy to just obliterate you.

[00:07:17]If the dying star is more than 15 stellar masses, its core collapses into a black hole.

[00:07:26]>> It's kind of astounding what the universe is doing. It's taking incredibly simple things like hydrogen atoms and using gravity to ultimately bring all this stuff together and make things like black holes.

[00:07:37]>> I find it quite beautiful how our whole cosmic history is the story of little things coming together into bigger things.

[00:07:46]>> But these stellar mass black holes are tiny flyweights. To step up to the heavyweight division, they have to grow billions of times more massive. But how?

[00:07:58]>> How do black holes become super massive?

[00:08:02]This is the age-old question. We're not really sure.

[00:08:07]>> The current state-of-the-art understanding of how black holes become super massive is like uh we're confused.

[00:08:14]Really don't know.

[00:08:16]>> We still don't know exactly how they become so big.

[00:08:21]But we do know that the process involves ultraviolence, death, and destruction.