In 2007, astronomer Duncan Lorimer was searching for pulsars in nine-year-old data when he found something he didnt expect and couldnt explain: a burst of radio waves appearing to come from outside our galaxy, lasting just 5 milliseconds but possessing as much energy as the sun releases in 30 days.

Pulsars, Lorimers original objects of affection, are strange enough. Theyre as big as cities and as dense as an atoms nucleus, and each time they spin around (which can be hundreds of times per second), they send a lighthouse-like beam of radio waves in our direction. But the single burst that Lorimer found was even weirder, and for years astronomers couldnt even decide whether they thought it was real.

The burst belongs to a class of phenomena known as fast radio transients objects and events that emit radio waves on ultra-short timescales. They could include stars flares, collisions between black holes, lightning on other planets, and RRATs Rotating RAdio Transients, pulsars that only fire up when they feel like it. More speculatively, some scientists believe extraterrestrial civilizations could be flashing fast radio beacons into space.

Astronomers interest in fast radio transients is just beginning, as computers chop data into ever tinier pockets of time. Scientists call this kind of analysis time domain astronomy. Rather than focusing just on what wavelengths of light an object emits or how bright it is, time domain astronomy investigates how those properties change as the seconds, or milliseconds, tick by.

In non-time-domain astronomy, astronomers essentially leave the telescopes shutter open for a while, as you would if you were using a camera at night. With such a long exposure, even if a radio burst is strong, it could easily disappear into the background. But with quick sampling in essence, snapping picture after picture, like a space stop-motion film its easier to see things that flash on and then disappear.

The awareness of these short signals has long existed, said Andrew Siemion, who searches the time domain for signs of extraterrestrial intelligence. But its only the past decade or so that weve had the computational capacity to look for them.

Siemion believes the fields rapid growth will revolutionize astronomy as a whole, not just his own search for ET. History has shown us that any time we sort of look into parameter space in astronomy any time we develop a capability to look in a new way we find something, he said. I think that our exploration of the time domain is just getting started. Were going to find things we never expected.

Lorimers discovery, which took his name, is one such unexpected find. The search for its mysterious origin initially energized the field. Everyone was really jazzed, said his research partner Maura McLaughlin, who first discovered RRATs. We thought the Lorimer burst could be a new kind of source. Some theorists suggest that it was a primordial black hole evaporating or a spark from a superconducting cosmic string.

Exotic possibilities, to be sure. But some scientists didnt think it was real. For a long time, Lorimer was the only one whod found a seemingly extragalactic burst, and doubts crept in. All we had were a few milliseconds of data from the late 1990s, said McLaughlin. I was even at a conference where somebody stood up and said, How many people here believe the Lorimer burst? Raise your hands. But Dunc always believed in his bursts.

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