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High-resolution simulations of the dark matter enveloping the Milky Way and its neighbour, the Andromeda galaxy.

Our astronomers have solved an outstanding problem that challenged our understanding of how the Universe evolved.

Our Milky way is orbited by a number of satellite galaxies that exhibit a bizarre alignment – they seem to lie on an enormous thin rotating plane – called the “plane of satellites”  

Standard cosmological model 

This seemingly unlikely arrangement had puzzled astronomers for over 50 years, leading many to question the standard cosmological model. 

This model seeks to explain 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 per cent of the Universe.  

As there is no known physical mechanism that would make long-lived satellite planes, astronomers thought the cold dark matter theory of galaxy formation might be wrong. 

Cosmological quirk 

Our new research, carried out along with an international team of scientists, has now found that the plane of satellites in the Milky Way is a cosmological quirk. 

Using data from the European Space Agency’s GAIA space observatory the researchers used supercomputer technology to project the orbits of the satellite galaxies into the past and future. 

They saw the plane of galaxies form and dissolve in a few hundred million years – a mere blink of an eye in cosmic time.  

Virtual satellite systems 

They also realised that previous studies based on computer simulations had failed to consider the distances of satellites from the centre of the Milky Way, which made the virtual satellite systems appear much rounder than the real one.   

Taking this into account, they found several virtual Milky Ways which boast a plane of satellite galaxies very similar to the one seen through telescopes.  

They say this removes one of the main objections to the standard model of cosmology and means that the concept of cold dark matter remains the cornerstone of our understanding of the Universe.  

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Main picture credit: Till Sawala / Sibelius collaboration (CC-BY).