A huge part of the matter in the universe is missing - again

Researchers from the University of Alabama observed space in the field of X-rays and tried to estimate the mass of the universe by the amount of radiation from the bingalactic material "We thought we saw the light of a billion aircraft carriers, but it was only a billion fireflies"

Not only has a huge chunk of the universe that astronomers thought was discovered in 2002 disappeared again, but it also took some friends with it, according to a recently published study at the University of Alabama at Huntsville (UAH). The new calculations may show that the universe is 10-20 percent thinner than previous calculations showed.

The same group at UAH that found what was believed to be a significant portion of the "missing mass" infecting the entire universe, discovered that some of the X-rays that were thought to be clouds of "warm" intergalactic matter now appear to have been created by light electrons.

"If the source of most of the X-radiation in space is from tiny electrons and not from heavy atoms, it's like a billion lights that we thought were coming from a billion aircraft carriers, turned out to be coming from a billion bright fireflies.

This means that clouds that emit X-rays contain a smaller proportion of matter than we have thought so far. ” says Dr. Max Bonamante, a professor in the Physics Department of the UAH.

"A large part of what we thought was the missing mass turned out to be those "relativistic" electrons that move almost at the speed of light (and therefore they are called relativistic), and collide with photons from the cosmic background radiation. The energy from these collisions turns the photon from a low-energy microwave into a high-energy X-ray.

The discovery was made when researchers tried to analyze the composition of hot gas emitting X-rays at the center of a galaxy cluster - the largest cosmological structure in the universe. In 2002, the UAH team reported that they had discovered a large amount of "soft" (meaning low-energy) X-rays coming from vast voids in the center of galaxy clusters. This discovery was added to previous discoveries of "hot" gas in these areas, which emit hard X-rays, i.e. high energy.

Although the atoms emitting the soft radiation were considered sparsely distributed in space (less than one atom per cubic meter), they fill billions upon billions of cubic light years. Their combined mass was thought to be responsible for at least 10% of the mass and gravity required to sustain galaxies, galaxy clusters and possibly even the universe itself.

When Bonamante and his colleagues looked at the data collected by several instruments operating on satellites, including the Chandra space observatory operating in the X-ray field, clustering galaxies in the southern sky, they found that the energy from those bodies emitting soft X-rays was not as visible as it should have been. "We were never able to collect spectral emission lines associated with these discoveries." explained. "If this difference in the data was due to impact with colder gas, we should have seen emission lines.

The most logical explanation is that a significant portion of the energy comes from electrons colliding with photons instead of hot atoms and ions, which had detectable spectral emissions. "Discovering these electrons, however, is like finding the tip of an iceberg," says Bonamante, because they may not be limited to emitting only soft X-ray signals. The signals from those electrons could also explain some of the observations of stronger X-rays, which would also reduce some of the reported observations of hard X-rays, and therefore also the mass that makes up the hot gas at the center of the galaxy clusters.

To complicate matters further, the energy from these electrons can also vaporize the cluster. Previously, astrophysicists used the energy coming from the center of these clusters to calculate how much matter was required to reach the equilibrium seen there. Too much mass and the cluster will collapse in on itself. Too little and the hot gas rose to spread. Since the energy coming from these hot clouds can be calculated in aggregate, it was believed that this mass could be calculated with great accuracy even for the astrophysicists. Instead, Bonamante says, if significant parts of the total X-ray energy comes from fast electrons, "this would throw us off guard and make us think there's more gas than there really is." This means that we will have to redesign the way we calculate both the gas mass and the total mass," he said.

per University of Alabama press release