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Mysterious bursts of rays solve puzzles about missing matter

The composition of matter in the cosmos is still a mystery to astrophysicists in many respects. If one looks at the movement of visible matter, for example, one can only come to the conclusion that there must be significantly more mass out there than can be directly observed. In particular, the speed of stars on the orbit around the center of their home galaxy indicates a considerable gap in the cosmic matter balance. In order for the calculation to be correct again, scientists postulate what is known as dark matter, the composition of which is one of the great open questions in cosmology.

If you add all of this up (and leave out the dark energy), then, according to the standard model of cosmology, the universe consists of around 85 percent dark matter and just 15 percent so-called baryonic, i.e. conventional matter. This results, among other things, from theoretical investigations into the course of the Big Bang and analyzes of the cosmic microwave background radiation. The result is a widely accepted assumption in the specialist world about how much baryonic matter, i.e. stars, planets, dust and gas, should be distributed in the universe.

Puzzling loophole

However, if you add up all observable matter, the next puzzling gap opens up: While dark matter makes itself noticeable through its gravitational influence, there seems to be no trace of more than 30 percent of normal matter. Around 20 percent are therefore bound in galaxies and their halos, and around 40 percent are likely to be made up by the gas clouds between the galaxies. The bottom line is that at most ten of the expected 15 percent of baryons can be determined using different inventory methods.

So where is the remaining third of that material that is made up of atoms? The search for it has now been going on for almost thirty years. In the end, however, a solution to this problem appeared to be emerging: Recent studies have indicated that the "lost" matter is hidden in the vast empty spaces between the galaxies and galaxy clusters, in the form of extended filaments of hot gas that look like thin threads span the cosmic abysses.

An atom in an open plan office

Difficulties in detecting this matter are of course its extremely low density, at least if one falls back on traditional observation methods and telescopes. Researchers compared the effort required to trying to find a single atom in an average open plan office. But now astronomers have found a way to illuminate this widely distributed matter, as it were, with the help of another puzzling cosmic phenomenon: the so-called Fast Radio Bursts (FRBs).

These rapid radio flashes are rare, high-energy bursts in the radio range of the electromagnetic spectrum that only last a few milliseconds and release enormous amounts of energy in the process. Their cause remains largely unexplained to this day, although the majority of astrophysicists assume that FRBs may be related to neutron stars. A team led by Jean-Pierre Macquart from Curtin University in Perth, Australia has now used these energy flashes as detectors for the missing matter.

Six FRBs was enough

"The radiation from the FRBs is scattered by the finely distributed matter between the galaxies in a similar way to sunlight, which is fanned out into its color components by a prism," says Macquart. "This fact helped us to determine the distances of some FRBs, which in turn gave us information about the density of matter between the galaxies. In order to detect the missing matter, we only needed six rapid radio flashes."

The Commonwealth Scientific and Industrial Research Organization (Csiro), co-author Ryan Shannon of Swinburne University of Technology, explained that the Australian Square Kilometer Array Pathfinder (Askap) radio telescope from the Commonwealth Scientific and Industrial Research Organization (Csiro) was the key to the findings published in the journal Nature. "The Askap has both a very large field of view, which can capture a section of the sky about 60 times the size of the full moon, and high resolution," said Shannon. "This means that we can record the FRBs relatively easily and then locate their home galaxies with extreme precision."

That, and the relationship between the distance of the lightning bolt and the way it propagates through the universe, eventually enabled Macquart and his team to quantify the density of electrons along the line of sight to the origins of the radio lightning bolts. In fact, the results obtained in this way agree with those values ​​that result from the cosmic microwave background and the assumptions about the Big Bang nucleosynthesis. (tberg, June 3, 2020)