Simulation of the cosmic “pancake”, seen from the side, with voids at the top and bottom.
A mere “blueberry” in this Universe: the Milky Way floats inside a “pancake” of dark matter, discovers a team in the Netherlands.
The Milky Way is not simply hovering in space. It is actually a “blueberry” from an authentic “cosmic pancake”.
The comparison is from , which reports this Tuesday on a new study, in Nature Astronomy, which suggests that our galaxy is embedded in a kind of sheet of dark matter.
The team led by the astronomer Ewoud Wempefrom the University of Groningen in the Netherlands, analyzed the motion of nearby galaxies to map the gravitational pull of invisible masses known as cold dark matter. The results suggest that local space is more structured than previously thought.
The study addresses three phenomena that intrigue astronomers: the Local Sheet, the Local Void and the calm Hubble flow. The Local Sheet is the structure where the Milky Way, the Andromeda galaxy and other neighbors meet, forming a surprisingly flat plane. Next door, the Local Void is an underpopulated region of space from which galaxies appear to move away. Hubble’s calm flow describes the uniform expansion of the Universe in this region, which is not easily explained with the mass of the Milky Way and Andromeda.
To investigate these enigmas, Wempe and colleagues analyzed the movements of 31 galaxies relatively isolated, whose data was collected over decades. They handpicked them because of their isolated position that makes them more reliable indicators of local expansion.
Based on this data, the team ran simulations that reproduced the mass distribution of the early Universe, derived from the cosmic microwave background. Simulations could only reproduce the observed movements if the mass was organized into a sheet-like structure, with empty, above and below.
This configuration elegantly explains the Local Sheet, the Local Void and the calm Hubble flow: the gravitational pull of the sheet concentrates matter on its surface, emptying the adjacent space and allowing a uniform expansion of the outer galaxies.
It is important to emphasize that this discovery does not require new theories. Sheets of matter are already known in the cosmic web, and the processes that formed them are studied in several works. Most notably, the dynamics of local galaxies require this structure, and that its existence is consistent with current physics and cosmological models.
“We explored all possible local configurations of the early Universe that could give rise to the Local Group. It’s great that we now have a model that is consistent with current cosmology and the dynamics of our local environment”, says Wempe.
