A brief, blazing burst of radio waves detected by the Arecibo Observatory could herald a turning of the tide for a peculiar class of cosmic signals. Until recently, the signals had only ever been detected by a telescope in Australia, a pattern that fueled doubts about their origin.

Fewer than a dozen of these bursts, lasting for only a few thousandths of a second, have ever been reported. Called “fast radio bursts,” the signals are cosmic enigmas that appear to come from the very, very distant universe. But since the first burst discovery in 2007, scientists have not only wondered what kind of cosmic object could produce such a tremendously bright, short-lived radio pulse – but have disagreed about whether the bursts are even celestial.

“There are more theories than there are bursts,” says West Virginia University astronomer Duncan Lorimer, an author on the paper describing the burst, posted to the arXiv on April 10.

On November 2, 2012, a blast of radio waves collided with the Arecibo Observatory in Puerto Rico, where the world’s largest single-dish radio telescope lives. Rain or shine, day or night, the 305-meter dish collects radio waves from the cosmos, which are then processed into data for scientists to study.

The data gathered at 6:35 am UT revealed a massive, 3-millisecond spike. Unlike the radio blasts emitted by some pulsars, the burst did not recur. It briefly blazed and then disappeared. Called FRB 121102, the burst was very similar to six earlier events that constitute the entire reported population of ultrafast radio bursts – a population that until November 2012 had only been seen by one telescope, in Australia.

But transience is only part of what makes these signals so weird. Their chief peculiarity lies in just how dang far away they seem to be.

Normally, radio waves travel at the speed of light. This means that all the different wavelengths and frequencies of radio waves emitted by the same object – say, a pulsar – should arrive on Earth in one big batch.

But if something is sufficiently far away, that changes. Longer, lower frequency waves traveling through the cosmos have a trickier time getting to Earth. Clouds of ionized interstellar particles – electrons, primarily – form roadblocks that slow and redirect these longer waves, causing them to follow a more sinuous path. As a result, the longer waves arrive just a bit later than their shorter kin – sometimes, the difference is only a fraction of a second.

That delay in arrival times is called “dispersion,” and it lets astronomers estimate how far away the waves are coming from. The longer the delay, the more intergalactic junk that got in the way. And since scientists think they know how much junk there is, they can use the dispersion measurement to approximate a distance, or at least identify whether an object lives inside or outside the Milky Way.

If astronomers are interpreting the bursts’ dispersion measures correctly, then the bursts came from billions and billions of light-years away – in other words, they’re nowhere near our cosmic neighborhood. And nobody knows what they are.

“The sources of the bursts are undoubtedly exotic by normal standards,” Cornell University astronomer Jim Cordes wrote in Science.

The ultrafast pulses take their name from Lorimer, who spotted and described the first burst in 2007. That mysterious signal, estimated to have traveled roughly 3 billion light-years before colliding with Earth, stunned astronomers. Many of them questioned whether it was an artifact produced by the telescope that detected it, the Parkes Observatory’s 64-meter telescope in Australia.

Full story at  http://phenomena.nationalgeographic.com/2014/04/20/mysterious-energetic-radio-burst/