Milky Way: The mystery of the galactic ring has been solved – Wikiwand

The Milky Way is not alone: ​​it is accompanied by many small satellite galaxies that form a belt around it – this has puzzled astronomers for decades. Because in reality there should be no such galactic ring. The satellite galaxies should be randomly distributed around the Milky Way, according to the standard cosmological model. So what is the unknown force that forces galaxies into this plane? However, as an international research team has now shown on the basis of more precise measurements, this supposed cosmic mystery is no mystery at all. So galaxies move on completely different scales. That their ring-like arrangement is purely coincidental. Scientists wrote that the supposed belt will melt again in a few hundred million years in the journal natural astronomy.

“The companions of the Milky Way almost line up the sky – and this has baffled astronomers for decades,” explains co-author Carlos Frink of Durham University in the UK. Because if satellite galaxies line up in the sky, they should all be inside a thin disk in space. “And explaining that is very difficult for cosmology.” It is very difficult to cast doubt already on the standard cosmological model and, in particular, on the idea of ​​\u200b\u200bmysterious dark matter researchers.

Because, according to current knowledge, visible matter—that is, stars, planets, or gas clouds—contributes only one-fifth of the total mass of the universe. Eighty percent of the mass is made up of dark matter. This is completely invisible and only reveals itself through its force of gravity. Dark matter plays an important role in the formation of galaxies in the universe.

The Gaia Space Telescope records the position and motion of about a billion stars

Computer simulations show how normal matter accumulates into large concentrations of dark matter. These concentrations are spherical, and the galaxies that form within them are randomly distributed. The focus in the disc cannot be explained in this model and also does not appear in the computer simulation.

Carlos Frenk and his colleagues have now used the best data yet from the European Space Agency’s Gaia space telescope to solve this mystery. Gaia has been in space since 2013 and provides precise position and motion data for about a billion stars not only in our Milky Way, but also in satellite galaxies.

The data assessment led to a surprise. Until now, astronomers assumed that small galaxies always moved in orbits within the disk. But this is not the case. Frink and colleagues’ conclusion: The currently observed concentration of satellite galaxies in a disk is purely coincidental. In a few hundred million years – this is a short period of time in cosmological terms – the disk will disappear.

Then the team took another look at the best computer simulations of galaxy formation to date. And in fact, these random disks can also be detected there. Until now, such random phenomena had been overlooked because researchers were only looking for evenly rotating disks of satellite galaxies. “We’ve solved one of the biggest challenges the cosmological model currently faces,” Frink says happily. “The dark matter model gives us a remarkably accurate description of how the universe has evolved.”