Mysterious signals coming from deep in space answer one of the universe's biggest puzzles

Astronomers have used mysterious signals coming from deep in space to solve one of the universe's puzzles.

Researchers used fast radio bursts – very intense, very short radio signals coming from a source that is still unknown – to find the universe's "missing matter".

Until now, researchers were unable to find half of the matter that they knew should be out in the universe.

Astronomers have long known that such missing baryonic matter must be somewhere, with models and research indicating that it has to exist. But for thirty years they have been unable to find it, which the scientists involved likened to a cosmic magic trick.

Now those signals have been used to locate that missing matter in the vast space between stars and galaxies, in a breakthrough new paper that relies on a technique that could go on to shed further light on other mysteries of the cosmos.

The researchers used the fast radio bursts to measure the material that they would have passed through on their journey between whatever extreme part of the universe has created them, and the Australian telescope that first detected them. By studying them with radio telescopes in Australia, they were able to measure how much matter they would have passed through on their way.

Researchers were then able to use optical telescopes to look at the galaxies that those fast radio bursts are being sent out from. That allowed them to be sure about how far those galaxies were – and by comparing those two measurements, they could understand the amount of material that must have been encountered on their journey.

Such advanced techniques were required because while there is a vast amount of missing material, it is very sparsely distributed through the universe, as well as being at a temperature that makes it hard to detect. It is so thinly spread that it is equivalent to looking for just a couple of atoms in a room the size of an office, said lead author Jean-Pierre Macquart, from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR).

The key discovery that allowed scientists to find that matter was the use of the fast radio bursts as "cosmological tools", he told The Independent. Likening them to a Swiss Army Knife, professor Macquart said that scientists hope to make many more such discoveries using the mysterious blasts to measure other parts of the universe.

That is despite the fact that scientists know very little indeed about the radio blasts, including where they come from and what extreme circumstances may be creating them. Professor Macquart likened it to the discovery of pulsars by Jocelyn Bell Burnell more than 50 years ago – the details of those radio emissions still remains mysterious, but they have been used as "precision clocks" to study other parts of the universe in ways that have led to Nobel Prizes.

"We don't need to know what the FRB is physically – what we need to assume is that it happens at one instant within milliseconds," said Bruno Leibundgut, Very Large Telescope programme scientist at the European Southern Observatory. "If you then have a bunch of photons let loose in one moment, then you don't need to know how they were created other than they have to start at the same time."

And while the latest discovery does not necessarily give any further information on the FRBs themselves, the research that underpinned it could. Scientists now have a detailed picture of the blasts and where they could be coming from within the universe, and hope to use that to understand more about the extreme conditions that give rise to them.

The amount of matter discovered is exactly in line with cosmological models that rely on the cosmic microwave background, which gives us a picture of the universe very shortly after the Big Bang, Professor Macquart said that the most surprising thing about the findings is that there was no surprise there at all.

"It tells us that our cosmological models are correct, and that the distribution of matter in the universe is as we know it," said Mariya Lyubenova from the European Southern Observatory, likening it to the discovery of Neptune, which was predicted indirectly from its disturbances of the orbit of Uranus before it was actually seen. "If this number had turned out to be different it would have caused very, very big challenges to our understanding. The distribution of matter does matter a lot."

Scientists also still only have relatively limited information about the nature of that matter, even if they now know that it exists. Professor Macquart likened the latest study to stepping into an unknown part of the map – researchers have got rid of the sign warning "here be dragons", but are still yet to characterise the specific coastline.

"What will be of interest next is to characterise the matter," said Celine Peroux,​ an astronomer at the European Southern Observatory who did not work on the study. "We now know the total amount – but what is its state? Is it hot, is it cold? Is it enriched with metals? The location and physical state of that matter is still unknown – and perhaps these objects will help with this."