By Marina Koren
The mysterious signals come from all directions in the sky.
No one knows exactly what they are, or what causes them, but astronomers have detected dozens over the past decade. The signals, known as fast radio bursts, originate from deep within the cosmos, well beyond the Milky Way galaxy. The radio waves travel across space for billions of years, moving at the speed of light. When they reach Earth’s telescopes, they make a brief and powerful appearance. For a few milliseconds, the bursts shine with the intensity of an entire galaxy. And then they’re gone.
Of the more than 50 recorded fast radio bursts, or FRBs, astronomers have a favorite: FRB 121102, named for the date of its discovery six years ago, on November 2, 2012. Unlike other fast radio bursts, this one repeats. Telescopes have observed blindingly bright flashes coming from the same point in the sky over and over, sometimes several times in less than a minute. The signal’s quirky nature has allowed astronomers to study it in more detail, to mine each flash for different kinds of information and even pinpoint its location in a small galaxy about 3 billion light-years from Earth.
Despite the nondescript name, FRB 121102 was one of a kind. Which raised a discouraging possibility: Could it be the only one of its kind? Each new pulse produced tantalizing data. But to really make sense of it, astronomers needed to find another—if any existed.
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