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Thanks to X-ray telescopes, scientists in the 1970s found the first real evidence that black holes actually existed, and astronomer Andrew Fabian has used X-ray research to unlock incredible mysteries ever since, including a giant sound wave that can travel through intergalactic gas!

This episode was made in partnership with The Kavli Prize. The Kavli Prize honors scientists for breakthroughs in astrophysics, nanoscience, and neuroscience — transforming our understanding of the very big, the very small, and the very complex. To learn more about Andrew Fabian’s work, go to

If you want to learn more about the 2018 Kavli Prize Astrophysics laureate, Ewine van Dishoeck, check out this episode on our main SciShow channel:

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This episode was made in partnership with The Kavli Prize.

The Kavli Prize honors scientists for breakthroughs in astrophysics, nanoscience and neuroscience — transforming our understanding of the very big, the very small, and the very complex. {♫Intro♫}. Most scientists do their jobs for the love of their field — a yearning to solve the puzzles of reality.

But it doesn’t hurt to get some international recognition along the way, like from The Kavli. Prize. The Kavli Prize is a partnership among the Norwegian Academy of Science and Letters, the Norwegian Ministry of Education and Research, and the U.

S.-based Kavli Foundation. And every other year, it awards three one-million-dollar Prizes. This year, the 2020 prize in astrophysics was awarded to Andrew Fabian for his breakthrough discoveries in observational X-ray astronomy.

Fabian is listed as the author on more than a thousand published papers. And amongst all those observations, he also got into the record books by discovering a black hole that makes the deepest sound in the known universe. Black holes might just be the most extreme objects we know of — especially supermassive ones.

Over time, they can grow to be as massive as a billion Suns. But they’re so dense that all that mass still fits into a package smaller than our solar system. Evidence suggests that most galaxies have these supermassive black holes at their centers, if not all of them.

And while they’re invisible to all forms of light, we can still study them, because they have a gravitational influence on stuff that’s totally visible. That includes the stars around them, and entire disks of gas and dust. In fact, the particles in those disks heat up and smash into each other so much as they fall toward their black hole, that they emit light across the electromagnetic spectrum.

Including X-rays! X-rays are blocked by our atmosphere, but once we figured out how to throw rockets and telescopes into space, we could really study them. Thanks to X-ray telescopes, scientists in the 1970s found the first real evidence that black holes actually existed.

And Andrew Fabian hit the ground running with his X-ray research at the same time. By 1995, he and his team had made an important discovery about black hole accretion disks, or those swirling pools of dust and gas that collect around black holes. By comparing how a specific set of X-rays looked at different locations in the accretion disk, Fabian’s team could estimate how fast a black hole was spinning.

A black hole’s spin is effectively only one of two properties we can measure — the other being its mass. And a spinning black hole acts differently than a non-spinning one: It affects how it interacts with the matter around it. So, Fabian’s crew figured out a really important method of measurement.

But his most famous discovery answered an even bigger question — an intergalactic mystery. And it involves galaxy clusters. If you look at a giant cluster of thousands of galaxies, it might seem like the space between them is empty.

But it’s not. It’s full of gas — although, nowhere near as full as like, Earth’s atmosphere. But there is enough that the gas can sometimes collapse and form new stars.

Except... when astronomers looked at that intra-cluster matter, that star formation wasn’t happening. The gas was too warm to clump together — millions of degrees hotter than it should have been based on what we knew. So, something was injecting energy into the system, and Fabian suspected black holes.

In 2002, his team used NASA’s Chandra space telescope to target a galaxy at the heart of the Perseus cluster. It’s roughly 250 million light-years from Earth, and it’s home to thousands of galaxies. It’s also super bright in X-ray light.

Chandra had checked out this galaxy before, and identified two large cavities in the region around it. These visible bubbles were made by jets of super fast particles stolen from the black hole’s accretion disk. And that opened the possibility that those jets were also heating up that gas and preventing star formation.

In their research, Fabian’s team found more detailed structures in that intergalactic gas — bright “ripples” just beyond one of the bubbles, spaced over 35,000 light-years apart. It was clear evidence of a pressure wave starting from the black hole, and moving outward. In other words, the jets were compressing parts of the intergalactic gas, making it brighter, and expanding the stuff in-between.

And a pressure wave is just… a sound wave. Yeah. It turns out that sound totally can travel through space, when you’ve got enough gas.

And because humans love putting things in context, that sound was calculated to be equivalent to a B flat… 57 octaves below middle C. You’d need a keyboard 15 meters long to play that note. Except you wouldn’t be able to hear it.

The lowest sound an average person can hear has a frequency as long as 1/20th of a second. This supermassive black hole sings at a frequency of 10 million years. Not only is this the deepest note in the universe, it takes an astronomical amount of energy to make it.

In fact, it takes the combined energy of a hundred million supernovas, and it has to have been sustained for at least the past 2.5 billion years. This isn’t just a super cool, record-breaking discovery, though. Fabian’s results demonstrated just how much power black holes have on their surroundings.

I mean, they’re basically stellar birth control: They shape how entire galaxies and even clusters of them evolve. Fabian didn’t get this year’s Kavli prize for this one discovery, of course. It’s for decades of research and discoveries.

And there are still questions to answer! Like, astronomers still need to work out how black hole spin influences this whole sound-wave-making, gas-heating process. And they need to study more clusters, and clusters at different ages to see how their black holes change their fates.

That’ll take more powerful X-ray telescopes — like the ESA’s Athena, which won’t come online until the 2030s. So, even when you get one of science’s most prestigious awards, a scientist’s work is never done. There are always more big questions to answer.

Thanks for the Kavli Prize for supporting this episode of SciShow Space. The Kavli Prize in Astrophysics is awarded for outstanding achievement in advancing our knowledge and understanding of the origin, evolution, and properties of the universe. So… big stuff!

They also award a nanoscience and neuroscience prize, honoring researchers for transforming our understanding of the small and the complex things around us. If you want to learn more about 2020’s Astrophysics laureate, Andrew Fabian, you can visit his page on the Kavli Prize website. We’ll include the link in the description.

And if you want to learn more about the 2018 Kavli Prize Astrophysics laureate, Ewine van. Dishoeck — well, we just posted an episode about her over on the main SciShow channel! You can check out her story after this. {♫Outro♫}.