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 out – to 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 quickly – but 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 years – no 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, anyway – the 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 all – but
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 place – there was what
looked like a big bubble of hot X-ray plasma in the center of the galaxy cluster.
This screamed explosion – but 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 plasma – in 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 slowly – think 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 it – the 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 initially – it’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 comprehend – basically, 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.