[♪ INTRO] In 2007, an astronomer named Duncan Lorimer discovered an oddly brief, strong radio signal that seemed to come from an unidentified source in space.

Astronomers were baffled. Usually, bursts of radio waves come in predictable, repeating patterns, like the ones we’ve detected from stars called pulsars.

This was totally new. At first, skepticism was high that this lone burst was important. Sometimes weird signals turn out to just be glitches, or we find out that they’re caused by interference from communications equipment on Earth.

But with more research, astronomers confirmed that the signal wasn’t just a glitch, and it came from at least 3 billion lightyears away. The question was: what caused it? 10 years later, we still have no idea. Since Lorimer’s initial discovery, we’ve found more of these signals.

They’re known as fast radio bursts, or FRBs, which is actually a pretty descriptive name: they’re quick bursts of bright light in the radio wavelength range of the electromagnetic spectrum. FRBs last just a few milliseconds, and so far, we’ve only been able to detect them from Earth by pointing telescopes in exactly the right direction at precisely the right time. But since we don't know where they come from, we don’t really know where to look or when to expect them.

Which is part of why we’ve detected less than two dozen FRBs so far. In the past decade, astronomers have come up with a few ideas about what might be causing them. One option is that the FRBs come from collapsing neutron stars, the rapidly spinning, ridiculously dense cores left over after certain stars go supernova.

If the neutron star is dense enough, it’ll be overcome by gravity and collapse into a black hole. But if it’s spinning fast enough, that can hold off the collapse for a little bit. When the neutron star eventually faces its doom, its magnetic field will be ripped apart, which could cause charged particles within the star to shoot out a quick, bright burst of radio waves, in other words, an FRB.

Another possibility is that FRBs come from two very dense objects merging, like black holes or neutron stars. As they spiral in toward each other, the merger causes tons of energy to be thrown out of the system, possibly in the form of a fast radio burst. Researchers have come up with lots of potential explanations like these, but they haven’t been able to confirm any of them yet.

The other issue is that these explanations only fit single, isolated FRBs. But in 2016, astronomers announced that they’d discovered 10 repeating bursts that all seemed to come from the same source. One possibility is that repeating bursts come from a magnetar, a special type of neutron star that’s super magnetic and spins especially fast.

These stars might produce FRBs when they send out flares. But even though these explanations might make sense in theory, they’re all just educated guesses based on the types of things researchers think could possibly send out brief, strong bursts of radio waves. This whole field of research is still really new, and astronomers don’t have much data to work with.

But they’re hoping to have a lot more soon. Based on how the number of bursts we’ve found compares to how long we’ve spent looking for them in different parts of the sky, researchers think an FRB might reach Earth as often as every 10 seconds. And they’re trying to catch as many of them as possible.

Most of the telescopes astronomers use are designed to be really sensitive, because they’re trying to detect the faintest signals. These telescopes can only focus on tiny areas of the sky at a time, so they’re not good at detecting unpredictable things like FRBs. But FRBs are so strong that you don’t need a super sensitive telescope to spot them.

Astronomers are planning to take advantage of that. One of the most promising projects, set to start at the end of 2017, will use the Canadian Hydrogen Intensity Mapping Experiment, or CHIME. CHIME is made up of four, hundred-meter-long open cylinders with multiple antennas, which will allow it to monitor much larger patches of the sky than other, higher-sensitivity telescopes that can only monitor one small area at a time.

Using CHIME, astronomers think they’ll be able to detect more than a dozen FRBs per day. Other projects are using telescopes that are even less sensitive, like one that will use an array of ten 5-meter-wide dishes to search huge patches of the sky. So, hopefully soon we’ll be detecting way more FRBs, which should help astronomers figure out which of their ideas are right.

Or maybe they’ll find out that all their ideas were wrong. Either way, we still have a lot to learn about what’s out there. Thanks for watching this episode of SciShow Space, and thanks especially to our patrons on Patreon who help make this show possible.

If you want to help us keep making episodes like this, you can go to patreon.com/scishow to learn more. And don’t forget to go to youtube.com/scishowspace and subscribe! [♪ OUTRO]