Astronomers say they have solved an outstanding problem that challenged our understanding of how the universe evolved-the spatial distribution of faint satellite galaxies orbiting the Milky Way.
These satellite galaxies exhibit a bizarre alignment-they seem to lie on an enormous thin rotating plane-called the "plane of satellites."
This seemingly unlikely arrangement had puzzled astronomers for over 50 years, leading many to question the validity of the standard cosmological model that seeks to explain how the universe came to look as it does today.
Now, new research jointly led by the Universities of Durham, U.K., and Helsinki, Finland, has found that the plane of satellites is a cosmological quirk which will dissolve over time in the same way that star constellations also change.
Their research removes the challenge posed by the plane of satellites to the standard model of cosmology.
This model explains the formation of the universe and how the galaxies we see now formed gradually within clumps of cold dark matter-a mysterious substance that makes up about 27% of the universe.
The findings are published in the journal Nature Astronomy.
The Milky Way's satellites seem to be arranged in an implausibly thin plane piercing through the galaxy and, oddly, they are also circling in a coherent and long-lived disk.
There is no known physical mechanism that would make satellites planes. Instead, it was thought that satellite galaxies should be arranged in a roughly round configuration tracing the dark matter.
Since the plane of satellites was discovered in the 1970s, astronomers have tried without success to find similar structures in realistic supercomputer simulations that track the evolution of the universe from the Big Bang to the present day.
The fact that the arrangement of satellites could not be explained led researchers to think that the cold dark matter theory of galaxy formation might be wrong.
However, this latest research saw astronomers use new data from the European Space Agency's Gaia space observatory. Gaia is charting a six-dimensional map of the Milky Way, providing precise positions and motion measurements for about one billion stars in our galaxy (about 1% of the total), and its companion systems.
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