Now for a very long time, camera ray bursts were the coolest, most exciting thing in astrophysics, these violent flashes of gamma rays from across the universe. However, there is now a new, or possibly even cooler type of explosion, the fast radio bursts. Now instead of coming out at camera ray wavelengths, the fast radio bursts come at radio wavelengths, hence the name, and instead of lasting seconds to minutes, they lost milliseconds. At the moment they are one of the biggest mysteries, unsolved mysteries, in astrophysics. Now we'll be puzzling that these have been discovered so recently, after all, radio telescopes have been around since the 1940s and 50s. However, it's very hard to pick up very quick bursts of radio emission, because there's so much interference that mimics it. But the first fast radio bursts was picked up in 2001, using this telescope, the venerable Parks Telescope, and here in Australia. And, no, what at the time noticed? They weren't looking for sudden flashes, they were actually mapping hydrogen gas in the magenta clouds at the time. And if you do see a sudden flash of radio, usually it's interference, I was once observing at the telescope pern in Arabeye, and was getting pulses of radio interference coming at the same time every day. It turned out it was a local farmer. Every time he started this car, there was a sudden flash of radio, which I could see the car at the window, and every time it started up, boom, mixing nor came through on the telescope if you could moment us away. This telescope, for a while, they were put devoured by microwave ovens. Every time the astronomers would heat up their food in the microwave oven, and they're living in quarters, a few minutes walk away from this, that would, and they'd open the door, a burst of microwaves would come out, and, oh, strange signal is it from space. Anyway, stars go, it was looking for a long time with very high frequency data, and several years later, a lorama at Al, we're looking at the data, and they saw a rather strange pattern. So what we've got here, there's the frequency in the geolets, and this is the time in milliseconds. What you can see is a curving, sloping line. If you try to cut through it at one point like here, you see there's a very narrow spike, only lasts five or ten milliseconds, what you can see is it happens earlier, a tie frequency, and later a later as you get to lower and lower frequencies. Now, most terrestrial interference, there'll be microwave ovens, satellites, mobile phones, any of the myriad of things that can jam our radio signals, you wouldn't get this trend with frequency, it would happen at the same time. This is what you expect if there's sudden radio bursts happening from very far away, outside our own galaxy, way outside our own galaxy. Now, if intergalactic space was empty, then the pulse would arrive all frequencies at the same time, but deep, intergalactic space is not quite empty, it's full of a very diffuse plasma, and as the radio waves go through this plasma, it actually slightly slows down at the lower frequency radio waves, it's called the dispersion relation. The high frequency ones are slowed down less, and the net result is you get a sliding scale. So the high frequency first, and the low frequencies later. So when they swap this, this has got a real, I mean it's very hard to get interference that produces that particular pattern, and it has to be, for outside our own galaxy, in our own galaxy you do get the dispersion, but it's much smaller than this, to get enough dispersion, enough plasma between us and the source, to get this big slope, it would have to be a very long way away. People were, I'd say, a bit skeptical, but as time went on, a few more were discovered, particularly when they were discovered by other telescopes as well, it became clear that we were looking at some sort of incredible, extragalactic radio burst. More recently, a number of new telescopes have come online, which can measure these far more efficiently, and pinpoint on the sky more accurately where they come from. This is the ASCAP, the Outback Western Australia, and this is Chimes in British Columbia Canada, and these two are the current leaders at spotting these things, getting accurate positions, and it's become clear these fast radio bursts happen many times a day. Most of them are not spotted because of the telescope, it's not looking at the right place at the right time, but they're actually incredibly common and frequent. Here are some more data on these things, and you can see a characteristic downward slope with the particular spikes here, some are brighter and some are fainted at others, but they're all very clear. If we get rid of the effect of the plasma and pregainthing version, you can plot the time here, it's the one here that's less than half a millisecond. This one may be about 10 or 15 milliseconds, and this one may be five or 10 milliseconds, so these are incredibly short, much shorter than gamma ray bursts. And in fact, this time is probably not caused by how long the actual radio burst goes on. Has the radio burst travels through space, you've got space with different amounts of plasma, and that will distort the rays as they come towards us and give us as delay. So it could well be the actual time of these things as much less than a millisecond. For this very short time, to produce that much radio emission in that shorter time so that we can see it far beyond the galaxy, these are briefly outshining the rest of the universe. What are they? Well, we don't know. To produce something this short, it must be a very compact object, and our best guess at the moment, we've been pointed where a couple of them come from, most of them we haven't got up to go counterparts, there are a couple to come from galaxies, hundreds of millions to a billion light years away, and most likely at the moment, we are thinking they are some form of highly magnetised neutron star freaking out in some way. To get such an intense emission over such a short time scale, we have to have cohere an emission like a radio. What that means is some signal starts propagating, as it propagates through the magnetic field, it causes more atoms or electrons to behave in a particular way, and builds up much like an laser or amazer. Only that could you see incredibly high intensity over the very short periods of time, and our best guess is it's probably something like a neutron star. The fact that we see so many of these radio bursts seems to indicate that they can't be like a supernova that destroys the object, it must be something that recurs in the same object otherwise, that it wouldn't be enough supernova going off in the universe to produce so many radio bursts. Do they repeat? Well a few of them do, there have been a few cases where we've seen repeat bursts from the same place, further indicating that it's some sort of freak out that doesn't actually destroy the object. It could be that all of them repeat, it's just that the time between repetitions may be so long we haven't yet seen it for most yet. I think there's one object that's been observed for like a thousand hours and we only saw the one flash, but maybe a thousand and one hours or ten thousand hours or a hundred thousand hours, there'll be another one. In fact a lot of people think they have to or repeat it, otherwise that just aren't going to be enough fard objects in the universe to produce all these flashes. So, be mystery, what are they? Something small and violent and go here and probably involving strong magnetic fields and neutron stars, maybe, maybe not, many theories are out there at the moment, but as we get more observations of them, particularly more follow up on other wavelengths, we hope you'll get a much better idea pretty soon.