Scientists have discovered dark matter surrounding a galaxy that already existed 12 billion years ago. According to space.comthis is the earliest evidence of the existence of this mysterious substance known at the moment.
This discovery indicated to scientists that dark matter in the early universe was less “clumpy” than most current cosmological theories predict. If further observations confirm this assumption, it could change the current understanding of how galaxies form and develop. In addition, the discovery may indicate that the fundamental laws that govern the development of the cosmos may have been different in the “infancy” of the universe.
The key to mapping dark matter in the very early universe is the cosmic microwave background (CMB), a kind of fossil radiation left over from the Big Bang that propagates throughout the cosmos.
Because light takes time to reach Earth, astronomers see galaxies as they were when the light left them. The farther away the galaxy, the longer its light travels to us, respectively, the further in time we see it. That is, the most distant galaxies of the Universe are observed as they were billions of years ago.
Observing dark matter is even more difficult. It is believed that it makes up 85% of the total mass of the Universe, but does not interact with matter and light, like ordinary matter. In order to “see” it, astronomers rely on the gravitational influence of dark matter on other objects.
The CMB is an earlier source of light than any galaxy. It came about when the universe cooled down enough to allow atoms to form, reducing the number of free electrons that scatter photons, in what cosmologists call the “final scattering.” The reduction in the number of free electrons allowed photons to travel freely, meaning that the universe suddenly ceased to be opaque and became transparent to light.
And just like light from other distant sources, the CMB can be distorted by dark matter galaxies due to gravitational lensing.
In the study, the scientists combined the lens distortions of a large sample of ancient galaxies with CMB distortions, revealing dark matter that existed when the universe was only 1.7 billion years old.
“For the first time, we have measured dark matter almost from the earliest moments of the universe. 12 billion years ago, things were very different. You see more galaxies that are in the process of formation than at present; the first clusters of galaxies are also starting to form,” said Yuichi Harikane, one of the scientists.
Scientists have previously stated that The universe may stop expanding. And it will happen “relatively soon.”