In 24 August 2001, the Parkes Radio Telescope in Australia picked up an unusual signal—an intense burst of radio waves coming from the direction of the Small Magallenic Cloud beyond our galaxy. The burst was odd because it was so short, less than 5 milliseconds in length, and strong enough to saturate the telescope’s receivers at certain wavelengths.

That puzzled astronomers. Clearly, they had seen some kind of rapid movement of charge—a spark. But what manner of spark could produce a signal capable of maxing out detectors on Earth after travelling a million light years through space?

Astrophysicists began to dream up all kinds of exotic mechanisms such as black hole collisions or even superconducting cosmic strings.

The mystery seemed to be solved when in 2010, astronomers at Parkes discovered 16 similar radio bursts. This time the explanation was less exotic. The signals appeared unresolved, as if they were too close to the telescope and the timings between some of them were suspiciously regular.

Astronomers eventually concluded that these sparks must have occurred in the Earth’s atmosphere, probably at an altitude of 20 kilometres or so. They called them Perytons, after the mythical beasts that were half bird and half stag.

Nobody knows what might generate Perytons in the atmosphere but whatever it is, perhaps the 2001 event was an unusual one of these, suggested some astronomers. It certainly shared some of their characteristics, although not all.

Then, last year, the mystery deepened again. Astronomers reported seeing four new powerful sparks once again from beyond our galaxy. Seeing four sparks—or fast radio bursts—in a short space of time in a small area of sky implies that there ought to be about 1000 of these events every day.

Suddenly the idea that the universe is filled with giant cosmic sparks was back on the agenda

Today, Shrinivas Kulkarni at the California institute of Technology and a few pals, attempt to clear up some of the controversy. These guys suggest that astronomers have discovered an entirely new phenomenon that occurs on a scale ranging from the terrestrial atmosphere to extra-galactic distances. And that this may kick start an entirely new field of radio astronomy.

The analogy these guys draw is with gamma ray bursts. These are the brightest electromagnetic events in the universe, producing highly energetic photons, probably during violent events such as a supernova or black hole collisions.

The discovery of gamma ray bursts is an interesting episode in the history of astronomy. The signals were discovered in the 1960s by US military satellites looking for the tell-tale signatures of nuclear tests in space.

These bursts were clearly not from nuclear weapons but astronomers had no idea where they might come from. They initially thought the bursts must be terrestrial in origin, then suggested they came from inside the Milky Way galaxy and later decided that the most powerful bursts come from the most distant reaches of the universe.

Today, astronomers know that gamma rays are produced by a rich variety of phenomenon. “Bursts of gamma-rays are now seen from atmospheric events, from the Sun, from compact stellar sources in our Galaxy, and from cosmological distances and that too from at least two distinct populations,” say Kulkarni and co.

So events that astronomers originally thought were generated by a single phenomenon now turn out to be generated by numerous mechanisms on scales ranging from the terrestrial to the cosmic.

Perhaps astronomers have stumbled onto something similar with Perrtons and fast radio bursts. “It may well be that astronomers are on a similar adventure in the radio band,” suggest Kulkarni and co.

These guys survey the evidence and say that Perytons are clearly terrestrial in origin. They say that on balance they think the 2001 spark must be terrestrial too. But they say the evidence that the fast radio bursts come from much further afield is more convincing, although by no means set in stone.

What’s needed of course is more measurements. If there are 1000 fast radio bursts every day, then these should soon reveal themselves to the more powerful Expanded Very Large Array radio telescope and the Very Long Baseline Array radio telescope. These should be able to settle the question of where these events are produced.

“A single detection of a fast radio burst by the Very Large Array will immediately establish an extra-lunar origin and that by the Very Long baseline Array an extra-solar-system origin,” point out Kulkarni and co.

These measurements should be made in the coming months, setting the scene for the denouement of a fascinating puzzle.

But in a sense this is only the beginning. If some of these events turn out to be extragalactic, then the important question is what causes such giant sparks and how can we study them in more detail.

And if these events are purely terrestrial, the same question applies—what causes them in the atmosphere and why haven’t we seen evidence of them before?

The most exciting possibility, of course, is that the signals are produced on both scales. In which case, both astronomers and atmospheric physicists will have exciting new fields on their hands.

Ref: arxiv.org/abs/1402.4766 : Giant Sparks At Cosmological Distances?