﻿Have you ever wondered what space sounds like?
I know, I know, sound can’t travel through a vacuum.
But that doesn’t mean the universe is silent.
Quite the opposite – it’s filled with different vibrations just waiting to be decoded.
Through a process known as data sonification,
scientists can turn data on plasma, x-ray, and even gravitational waves
into something we can actually hear.
In past videos, we explored the haunting sounds of Saturn,
Earth’s magnetosphere,
and the Sun’s solar flares.
But today, we’re diving head-first into the most terrifying sounds space has to offer,
from the ghostly wail of a passing comet
to a growling supermassive black hole,
to the echoes of a black hole collision from 5 billion years ago.
So, what do these phenomena sound like?
And what do their sounds teach us about the cosmos?
We’re about to find out.
I’m Alex McColgan, and you’re watching Astrum.
Join me today, as we tune into four of the scariest sounds in space.
We’ll explore how scientists have captured these bizarre sounds and why they matter.
As the saying goes, “In space, no one can hear you scream."
That’s because sound waves require a medium to propagate
and vacuums are, well, medium-less.
But other kinds of waves –
such as radio, plasma, x-ray, or gravitational waves –
can be converted into audio through data sonification.
But the results are more than just cool sounds.
Each audio clip carries distinct and important information
about celestial objects and phenomena,
such as solar winds, pulsars and black hole collisions.
Just as data visualisation lets scientists spot patterns more easily,
sonification allows researchers to detect patterns, trends,
or anomalies within complex data sets.
You might have seen one of my videos about sounds in space before.
They mainly focused on planets and the Sun.
But today, I’ll be sharing newer findings from more obscure places,
like the first successful probe landing on a comet,
and a supermassive blackhole in the Perseus cluster.
Before we get there, our first stop on this audio tour is a little closer to home.
If you’ve been watching this channel for a while,
you might remember my video on the sounds of Saturn.
Here, I want to focus on its spectacular rings –
one of the landmarks of our Solar System.
Saturn’s rings are made up of countless particles of rock and ice.
Most of these particles are electrically charged,
mainly due to the ionizing effects of solar radiation.
Saturn’s magnetosphere is also filled with charged particles,
which are free to move, interact,
and form other complex phenomena – they aren’t fixed in one place.
In a nutshell, when charged particles in Saturn’s rings
interact with the plasma in its magnetosphere,
they experience what’s known as the Lorentz force.
This force makes particles spiral around the
magnetic field lines and create oscillations in the plasma –
also known as plasma waves.
In 1997, NASA launched the Cassini probe to study Saturn up-close.
One key part of the mission was to explore Saturn’s ring-plasma interactions more deeply.
As the spacecraft passed through Saturn’s ring system,
its Radio and Plasma Wave Science (RPWS) instrument
recorded the waves produced by the charged particles in the rings.
This instrument is incredibly sensitive –
so sensitive it detected lightning in Saturn’s atmosphere from thousands of kilometers away.
Saturn’s thinnest rings contain dust particles just 200nm large – the size of a virus.
When these dust particles collide with the instrument’s detector,
their impact creates tiny puffs of plasma.
The plasma impacts are then converted into sound,
allowing scientists to “hear” the electromagnetic interactions taking place.
And the results are totally eerie.
It feels like the kind of thing we as humans aren’t even supposed to hear.
Here, have a listen.
But there’s more.
In 2017, Cassini’s Grand Finale orbits captured one particularly haunting “recording” of plasma
waves moving from Saturn to its moon Enceladus. What makes this clip more
haunting is that it was one of the last clips ever sent back by Cassini. Two weeks later,
the probe was deliberately plunged into Saturn’s atmosphere, after twenty years
of loyal service to humanity. Imagine this being the last thing you’ll ever hear …
Cassini wasn’t the only probe to send us back data on vibrations near a celestial body.
In 2014, ESA’s Rosetta probe sent back some trippy data on a passing comet you won’t want to miss.
Our second stop is Comet 67P. The object of ESA’s Rosetta mission,
it is the first and only comet to ever be successfully landed on by a man-made
lander. Comet 67P orbits the Sun in the outer solar system, roughly every six-and-a-half
years and is thought to house several primitive materials from the formation of the solar system,
over 4 billion years ago. On top of studying these materials, Rosetta’s mission was to understand how
solar winds affect the comet’s coma and tail. To do this, they armed the spacecraft with a
suite of plasma detection tools, including the Langmuir probe to measure the electron
density and plasma oscillations in the comet's environment, and a magnetometer to detect magnetic
field fluctuations caused by these plasma waves. Together, the data provided a comprehensive view
of the plasma dynamics around the comet. But this in itself wasn’t a breakthrough.
Magnetic-field sound waves had already been detected from other comets, including
the famous Halley’s Comet. What was special about comet 67p is the actual sound it made.
Comet 67p’s song was very different to the sounds measured from other comets before it, suggesting
it had very different physical properties. I’ll play it for you now.
What’s interesting is that this audio can be broken down into distinct components.
The rhythmic clicking sound represents the periodic fluctuations in the plasma's
density and the way the comet's magnetic field is disturbed by solar wind. The humming
parts of the sound reveal the continuous oscillations within the plasma environment.
Here, I’ll play it for you one more time. Honestly, to me it just sounds like the
demogorgon from Stranger Things. Speaking of Stranger Things,
our third stop on this tour is the closest thing we have to an Upside Down in this
reality. Ever wonder what sound a black hole makes? Buckle up, we’re about to find out.
Travel some 240 million light years from Comet 67P and you’ll end up in the Perseus
Galaxy. At its centre lies one of the largest known black holes in the Universe – estimated
at a whopping 17 billion solar masses. Supermassive black holes like this one tend
to emit intense X-ray and ultraviolet radiation due to the searing hot gas in their accretion
disk – we’re talking millions of degrees Kelvin. NASA’s Chandra X-Ray Observatory is a space
telescope in high-Earth orbit, tasked with looking out for X-ray data that might give
us insights into the nature of black holes. It carries a highly sensitive electronic detector
that captures incoming X-ray photons and converts them into digital signals, which lets scientists
map the hot gas distribution of black holes, supernova remnants, and galaxy clusters.
In 2003, it captured some tantalizing data. Chandra's high-resolution imaging and
spectroscopic capabilities allowed scientists to study the X-ray emissions from the black hole and
the surrounding hot gas in the Perseus cluster. In 2022, scientists revisited this X-ray data
and translated the frequencies into sound. By complete accident, they stumbled upon the
lowest frequency sound ever found in the Universe – a droning B-flat note 57 octaves below middle
C. At such a low frequency, the period of the sound wave coming from the black hole is 10
million years long. Humans can’t hear anything with a period longer than 50 milliseconds.
Through data sonification, NASA scientists transposed this black hole’s song by a factor
of quadrillions, into the audible range for human hearing. The results? A tormented,
guttural sound that’ll make the hairs on the back of your neck stand up. Here, see for yourself.
Creepy right? But what does it actually teach us about the science of black holes?
Many things – but perhaps most interesting is its implication on galaxy cluster evolution. In a
galaxy cluster, which can contain anywhere between a few hundred to several thousand galaxies,
the spaces in between are filled with thin gases and plasma. Also known as the intracluster medium,
it’s about six times denser thicker and hotter than the gas found outside galaxy clusters.
One theory is that the sound waves emitted by the black hole
are actually partially responsible for the temperatures in the intracluster medium,
since they carry energy. And since we know star formation is partially regulated by temperatures,
it’s therefore possible sound waves play some kind of role in
the evolution of galaxy clusters over time. Our fourth and final stop is something of a
triumph. Even Einstein doubted humanity would ever be able to detect what I’m
about to show you. If he were around to watch this video, I think he’d absolutely freak out.
Back in 1916, Albert Einstein predicted that black holes emanate gravitational waves.
Imagine throwing a rock into a pond. The water ripples. You can think of gravitational waves
like those ripples – except instead of acting on water, they act on the fabric of space-time,
ever-so-slightly stretching and contracting it as it passes. These disturbances were predicted
to be so small, that even Einstein himself didn’t think humans would ever be able to detect them.
Fast forward to today. In just over a century, we’ve managed to build a global network of
observatories that have picked up on gravitational waves from about 100 cosmic events. For example,
there’s the Laser Interferometer Gravitational-Wave Observatory,
or LIGO, in the US, the VIRGO in Europe, and the KAGRA in Japan – which all work
together to corroborate data and pinpoint the wave’s direction and source location.
If you aren’t familiar with their setup, the way these instruments work will surprise you,
because they’re nothing like traditional telescopes. They don’t use lenses – instead
they rely on something much more fun – lasers! Scientists send lasers down two perpendicular
tunnels, several kilometres long. When gravitational waves from space arrive at Earth,
they cause tiiiiny disturbances in the fabric of space-time, which is picked up by these lasers.
And I mean tiny – something like 10-18m, or one 10,000th of a proton. As the lasers' paths are
stretched or contracted by the gravitational waves, they emit different frequencies,
kind of like the strings of a guitar. A higher frequency is a higher pitch.
Converting this data into sound is how we get the signature “chirp” of a black hole collision.
Each collision has its distinct personality. Long, low buildups like this one:
…indicates a slower collision between pretty lightweight black holes. Faster,
heavier black holes sound more like this: You just heard the sound of two black holes
combining to form an even bigger black hole, 5 billion years ago. It’s the most massive
and distant gravitational-wave source ever observed, emitting about the energy equivalent
of five solar masses in gravitational radiation. Pretty epic, if you ask me.
As you can see, regarding space as silent is an oversimplification. Sound can’t travel
through vacuums, sure. But for those who dare to listen, the Universe reveals its
own haunting symphony. It’s just a matter of knowing where, and how, to lend an ear.
Thanks for watching! If you liked this tour of the cosmos, you might like this
one where I take you through the latest Euclid images and what they’ve taught us so far about
dark matter and the origins of the Universe. Click here to watch it now. See you next time.