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  • Do you know what a black hole is?

  • Unless you've never attended a science class or you've been living under a rock most

  • your life, you probably think you do.

  • But chances are, you're wrong.

  • I'm not being presumptuous, so don't roll your eyes at me like that.

  • We only have to go back to 2005 to reach a time where the world's top scientists had

  • it all wrong.

  • In fact, their mistaken ideas almost led them to miss out on discovering a very, very big

  • explosion

  • The textbook definition of a black hole is 'a place in space where gravity pulls so

  • much that even light cannot get out.'

  • Or, in layman's terms, it's a thing that sucks other things in.

  • But not everyone realizes that black holes also spit stuff outto be precise, they

  • expel jets when a disk of plasma accumulates around the sinkhole in the middle.

  • Scientists previously thought that black holes only suck stuff in when they're relatively

  • small, allowing them to grow quicklybut that, once they reach a certain size, this

  • process stops.

  • Well, that turned out to be incorrect, and it only took the discovery of a crazy-huge

  • explosion to figure it out

  • One day, scientists were studying the galaxy cluster named MS 0735.6+7421, which is a disappointingly

  • boring name for something as cool as a galaxy cluster.

  • It's literally one of the largest structures in the universe, containing thousands of galaxies,

  • dark matter, and hot gas.

  • This particular cluster is around 2.6 billion light years away from us, so maybe they'd

  • used up all the catchy names by the time they came around to it.

  • But it does lie in the constellation Camelopardalis, also known as the Giraffe.

  • Now there's a name I can get behind!

  • But anyway, these guys noticed something intriguing.

  • Not only was there a huge black hole, but that black hole was growing.

  • Fast.

  • But that didn't make any sense, because the black hole was already massive, and should

  • have stopped expanding.

  • In fact, the amount of matter that had been swallowed was so large that researchers weren't

  • even sure where it had come from.

  • Had the gas from the host galaxy cooled and then been swallowed?

  • And there was another strange thing, too.

  • There were two huge cavities in the galaxy cluster, extending away from the black hole.

  • As if something had caused those cavities.

  • Are you thinking what I'm thinking?

  • But the idea of the black hole causing the cavities should have been impossible.

  • For one, everything known about black holes suggested that this one should have stopped

  • expanding.

  • And secondly, if it was true, we'd be talking about the biggest explosion ever.

  • Or at least, the largest since the Big Bang.

  • It was a big deal, and the researchers needed to get to the bottom of it.

  • Using a mix of radio and X-ray telescopes, scientists were able to piece the information

  • they found together.

  • The cavities were created by the black hole, after jets erupted from within the hole and

  • released a load of gravitational energy.

  • The scale was beyond anything we'd encountered before.

  • The supermassive black hole had been greedily swallowing ridiculous quantities of dark matter,

  • and a mass equivalent of 600 million solar masses.

  • Yes, you heard that right, 600 million.

  • Does that help you to get a scale of just how big this explosion was?

  • But you can't think of this eruption in the same way as you'd think of a bomb going

  • off on our tiny planet, or even in the same way as a volcano erupting.

  • It wasn't just a one-off event lasting a few minutes or hours, or even a few days.

  • In total, it's estimated that the explosion happened over one hundred million years of

  • energy release.

  • Hundreds of millions of gamma-ray bursts would be needed to release that level of gravitational

  • energy.

  • One hundred million years of gamma-ray bursts, X-ray emitting gas, and matter repeatedly

  • being swallowed into the black hole and spit out again.

  • Meanwhile, we start to feel old when we turn thirty.

  • Each of the cavities created are thought to be around 700,000 light years wide.

  • It's difficult to comprehend a void so large you can only measure it in thousands and thousands

  • of light yearsno wonder the discovery was groundbreaking.

  • To get an idea of the size, try to picture this: the amount of displaced gas was equal

  • to a trillion suns, and it had more mass than all the stars in the Milky Way.

  • Plus, the black hole involved had the mass of over 10 billion solar masses.

  • And the sun has a mass around 330,000 times greater than that of the Earth.

  • And the mass of the Earth compared to you?

  • It doesn't even bear thinking about.

  • But the craziest part is that the explosion could still be happening right now

  • Thanks to the energy the explosion produced, hot gas around the black hole stopped cooling

  • and magnetic fields were generated in the galaxy cluster.

  • It's just one example of how explosions in space can develop and change the environment.

  • As for how black holes work?

  • The eruption helped to share some light, but it's one of the many mysteries of the universe

  • we're still uncertain about.

  • And which came first, anywaythe galaxy or the black hole?

  • So, basically, scientists uncovered a pretty big explosion.

  • But don't go yet.

  • You didn't really think that was the biggest explosion since the Big Bang, did you?

  • That's so 2005.

  • Don't worry, we can do way better than a black hole that sucks in three hundred suns.

  • It's time to talk about the explosion that released about five times more energy.

  • No wonder nobody bothered to think of a better name for the MS 0735.6+7421 galaxy cluster!

  • But first, let's talk about how the scientists can even determine when a really big explosion

  • has happened.

  • We mentioned that scientists used a mixture of X-ray and radio telescopes to put together

  • the pieces.

  • It goes without saying that we can't tell what's going on in space without a telescope

  • everything is happening hundreds of millions of light years away from us, after allbut

  • using one type alone isn't sufficient.

  • Different substances in space emit different types of radiation, and looking at all of

  • them gives a clearer picture.

  • So firstly, the X-rays.

  • Doctors use X-rays to figure out what's going on beneath the skin.

  • That's because X-rays are a form of light more energetic than anything we can see, and

  • their energy helps them to pass though more materials, including bones.

  • Well, X-ray astronomy works in the same way, but in reverse: things in space release X-rays

  • like black holes, stars, the Sun, and more.

  • But the telescope is like the detector that lets the Doctor see if a patient has broken

  • a bone or has a coin stuck in his throat.

  • This way, the researchers can see both the objects in space giving off the X-rays, and

  • anything that stops the transmission of X-rays.

  • The emitters appear as pretty fluorescent colors, whereas the blockers look like shadows.

  • But researchers also used radio telescopes.

  • As you'd expect, these are used to visualize radio waves, like those stars, galaxies, and

  • black holes emit.

  • The two types of telescopes are very different.

  • Firstly, they just look different.

  • Radio telescopes look like giant satellite dishes, whereas X-ray telescopes are more

  • like giant barrels with wings on each side.

  • Forgive the crude descriptions.

  • And they work differently, too.

  • Radio telescopes can do their job on the earth's surface, and you can often find them in open

  • spaces like fields.

  • By contrast, since the Earth's atmosphere absorbs X-rays, NASA's Chandra X-ray observatory

  • is located at an altitude of 139,000 kilometers in space.

  • Once upon a time, nobody would have detected huge eruptions in space because of the methods

  • used.

  • The old technique was to observe only bright central radiation, but that doesn't always

  • reveal what's happening.

  • Sometimes, there's no bright central radiation involved in an explosion, but there are different

  • types.

  • X-ray observations can reveal the hot cluster gas, whilst radio telescopes detect magnetized,

  • high-energy electrons.

  • This paints a fuller picture of what's happening.

  • But where were we?

  • Talking about some kind of explosion?

  • Oh yeah, the actual biggest explosion since the big bang.

  • Well, I hope you were paying attention to me ranting on about science, because it's

  • going to come in handy for this next part.

  • And if you're not prepared to face how tiny you are compared to the immense size of the

  • universe, then I suggest you stop watching now.

  • Have you heard of the infamous blast that happened in Mount St Helens in 1980?

  • It was one of the biggest eruptions in US history, so strong it literally ripped off

  • the top of a mountain, killing thousands of animals and destroying hundreds of homes.

  • Well, we're talking about something that was kind of like the space version of that,

  • only way bigger.

  • Now, we're dealing with the Ophiuchus galaxy cluster, which lies 390 million light years

  • away from earth.

  • The Ophiuchus galaxy had always been viewed as curious and puzzling to scientists, which

  • is why they paid so much attention to it in the first place.

  • The funny thing was, it had a curved edge to it.

  • Why could that be?

  • Galaxy clusters come in all shapes and sizes, but this was particularly suspicious.

  • So, they thought the curved edge could be the wall of a cavity caused by a huge black

  • hole in one of the core galaxies, shooting out plasma.

  • Because black holes don't just suck stuff in, remember?

  • So, the scientists had learned something.

  • But still, they assumed an explosion couldn't possibly have taken place.

  • Naïve as ever, they thought it would just have to be too unimaginably big, and the cavity

  • too incomprehensibly huge.

  • But, as I've already given away, that turned out not to be the case.

  • To investigate, they used the trusty X-ray telescope.

  • The results certainly seemed to suggest an explosion had taken placethere was what

  • looked like a big bubble of hot X-ray plasma in the center of the galaxy cluster.

  • This screamed explosionbut it didn't necessarily mean the explosion had caused

  • the cavities.

  • They needed more evidence.

  • So, low-frequency radio telescopes were used too, which revealed that the cavity was filled

  • with radio plasma.

  • Put together, the data basically proved that plasma from the black hole had caused the

  • cavity.

  • And there you have it: the biggest explosion since the Big Bang, greater even than the

  • eruption discovered in 2005.

  • But just how big a bang did this bang make?

  • First, let's talk about the cavity that formed in the cluster plasmain case you're

  • not a space geek, that's the hot gas that surrounds the black hole.

  • If you were to move from one side of the hole to the other, it would take one and a half

  • million light years.

  • How can we even comprehend that?

  • Another way to see it is that the crater was so big, it's more or less equivalent to

  • 15 Milky Way galaxies.

  • I know your next question.

  • How big is the Milky Way galaxy?

  • Scientists estimate it's around 100,000 light years wide, and that us here on Earth

  • are 165 quadrillion miles from the black hole in the galaxy.

  • It's hard to put the whole thing in human terms, but one scientist tried to explain

  • it by saying that the explosion would be like setting off 20 billion billion megatons of

  • TNT every thousandth of a second for 240 million years.

  • I'm not sure if that makes me more or less confused.

  • Of course, like the second-largest explosion, it happened extremely slowlythink hundreds

  • of millions of years.

  • It's hard to imagine it, but hey, that's what happens in galaxies far, far away.

  • And there you have itthe biggest explosion since the Big Bang.

  • At this point, you're probably wondering just how big the Big Bang explosion was in

  • the first place.

  • Well, I'm afraid nobody knows.

  • We don't know much about the Big Bang at all.

  • But we can guess, which is almost as good, right?

  • Nobody knows quite how the Big Bang happened initiallyit's way too complex for our

  • tiny brains to comprehend right now.

  • How could an explosion take place if there was nothing there in the first place?

  • Wouldn't something have needed to exist before?

  • But how would that thing of been created?

  • It's all very confusing

  • But a fraction of a second after it happened, we can start to have a better idea of what

  • was going on.

  • As soon as the explosion started, the universe began to dramatically expand at a speed we

  • can't comprehendbasically, that was the bang.

  • A really large expansion.

  • It took what was out there, just a few bits of stuff floating, to a whole universe with

  • various galaxies.

  • So, how big was it?

  • We don't even know how big the universe is now, so it's impossible to say.

  • We just know it has been constantly expanding at an ever-increasing pace ever since the

  • Big Bang.

  • It could even be infinite.

  • But it's fair to assume that since it created everything else, it was probably the biggest

  • explosion.

  • If you find your cosmic insignificance strangely soothing, check out our videos about invisible

  • galaxies or strange things spotted inside black holes.

Do you know what a black hole is?

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Scientists Shocked By Biggest Explosion Since The Big Bang

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    林宜悉 posted on 2021/01/05
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