PerthWith the help of cosmic radio flashes, astronomers have tracked down the long-sought-for missing matter in space. The discovery completes the matter inventory of the universe exactly according to the models and predictions, the researchers led by Jean-Pierre Macquart from the International Center for Radio Astronomy Research Icrar in Perth, Australia, report.
At the in Specialist journal Nature Published investigation is about the common, so-called baryonic matter, of which stars, planets and humans are made, not about the mysterious dark matter, which has to be around five times more common.
Short radio flashes (Fast Radio Bursts, FRB for short) have only been known for a few years. They twitch through apparently random directions through the cosmos without any apparent warning. Their nature has not yet been clarified, but the short bursts in the wavelength range of the radio radiation obviously come from the depths of space. For a handful of lightnings, the origin galaxy has been successfully determined. Accordingly, they have to send out as much energy as our sun in 80 years in one fell swoop in order to be measurable over the gigantic distances.
On their long journey through the universe, the flashes of radio illuminate the thin matter in the cosmos. “We know from measurements of the Big Bang how much matter there was at the beginning of the universe,” explains Macquart. “But when we looked into the universe today, we couldn’t find half of what was supposed to be there. That embarrassed us a bit. ”The big shortfall is due to the fact that only a small part of the baryonic matter has clustered into shining stars. In fact, 90 percent of ordinary matter is not in galaxies, but in the vast expanse between them.
“The intergalactic space is very barren,” Macquart emphasizes. The missing matter corresponded to only one or two atoms in a room the size of an average office. It was therefore very difficult to find this matter with the conventional techniques and telescopes. Instead, the scientists used a special property of radio flashes: depending on the wavelength, they are slowed down very slightly when they pass through baryonic matter. “The radiation from the short flashes of radio is pulled apart by the material we are looking for, just as you can see it in sunlight, which is divided by a prism,” explains the astrophysicist.
The strength of this so-called dispersion shows how much matter a radio flash has passed on its way through space. If the distance to its origin is known, the average matter density in this direction of the universe can be calculated. Another team of researchers had already analyzed a short radio flash in this way four years ago. A similar result was reached – however, doubts arose later as to whether the assumed original galaxy was actually the source of the lightning. In addition, the study was only able to deliver the density of matter in one direction.
“We were now able to measure the distance from enough short radio flashes to determine the density of the universe,” emphasizes Macquart. “We only needed six to find the matter we were looking for.” Accordingly, baryonic matter, in line with the current model, represents around 15 percent of the total mass in the universe. The physically invisible dark matter, which is only noticeable by its gravity and whose nature is completely unknown, is over five times more common. (dpa / fwt)
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