If you listen closely, you may hear motorcycles approaching from the distance. Or maybe it sounds more like bees swarming. Perhaps it just sounds like a sci-fi background tone, meant to build tension. Whatever you think two neutron stars sound like as they spiral closer and closer together, though, it’s hard to deny that that final bloop isn’t startling — and even a bit silly.

On Monday, astronomers announced that they had observed gravitational waves sent out by two merging neutron stars for the very first time.

This is perhaps the most exciting discovery yet from the international collaboration between the U.S.-based Laser Interferometer Gravitational-Wave Observatory — LIGO — and the Italian Virgo observatory.

neutron star merger.
The two merging neutron stars produced lots of energy, but they didn't make any sound.

And even though this colossal merger didn’t make any sound, we can listen to a simulation of what it sounded like. It may seem strange that two ultra-dense neutron stars — each the size of our sun or larger — merging 130 million light-years away didn’t make noise. In the process, these merging stars produced massive amounts of gamma radiation and even created elements like gold and platinum.

But, perhaps most importantly, they also produced ripples in spacetime. These ripples, which we know as gravitational waves, occur at various frequencies, which scientists can translate into sound. Without further ado, here’s what this merger “sounded” like:

As you can see, the previous merger measured by LIGO and Virgo were much briefer. The reason for this is the fact that this merger involved neutron stars, not black holes.

“While earlier detections of the black holes that we’ve made … only lasted for us a couple of seconds, or much less, this neutron star in-spiral lasted for over a minute,” LIGO spokesperson David Shoemaker told reporters on Monday. Inverse reported on how this affects the merger:

The reason for this longer detection is that neutron stars, the smallest, densest stars known to exist, are much lighter than black holes. Whereas the merging black holes that created earlier gravitational wave detections were many times larger than the sun — the first detection in 2015 involved black holes of 29 and 36 solar masses — the neutron stars involved in this latest detection were only about the mass of the sun or maybe twice the mass of the sun.

So as the neutron stars spiraled in toward one another, they emitted high-frequency gravitational waves that fell within the range that Earth-based detectors could record.

“The result is that we can see the system for some 1,500 complete cycles of these two objects around each other,” said Shoemaker.

And that final bloop? That’s when the stars finally merged. By converting the frequency of gravitational waves into audio, the astronomers created what could potentially be the sickest hip-hop beats of all time.


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