Dark matter riddle comes to light

Latest research suggests that dark matter is more evenly spread across the Universe than previously thought

Researchers say that invisible dark matter is around 10 per cent less clumpy than expected and maps of more than 30 million galaxies reveal a smoother sweep of the elusive material than predicted by the leading theory about the Universe’s early expansion. The theory – based on knowledge of the Universe’s make-up right after the Big Bang – predicts that dark matter should be dotted around the Universe in denser clumps than the astronomers have observed.

An international team used a telescope at the European Southern Observatory in Chile to study the light emitted by millions of galaxies – some more than 10 billion light years away. Analysing how the gravitational tug of dark matter altered the direction of emitted light enabled the team to map out the matter in the Universe. Professor Catherine Heymans, of the University of Edinburgh’s School of Physics and Astronomy, who led the research team, said:

The results are fascinating as we directly map out the mysterious dark side of our Universe

Unidentified gaps in the standard model of Cosmology could explain why the team’s findings about dark matter – which has never been directly detected – differed from predictions. Dr Marika Asgari, from the University of Edinburgh, who co-led the analysis, calls the result 'intriguing':

The standard model of Cosmology relies on rather mysterious physics that we call dark matter and dark energy.  Scientists have to test this remarkable model in as many ways as possible, and that is exactly what we are doing

The latest findings from the Kilo-Degree Survey (KiDS) appear in five articles submitted for publication in the journal Astronomy & Astrophysics. The work was co-led by scientists from the University of Edinburgh, University College London, the Ruhr-University Bochum in Germany and Leiden University in The Netherlands. The research builds on previous work by the KiDS team to map 15 million galaxies. Dr Tilman Tröster, from the University of Edinburgh, who co-led the analysis, said:

The KiDS results may indicate small cracks in the standard model, just like another discrepancy in the expansion rate of the Universe, the so-called Hubble constant. The question is whether these can be solved with a small adjustment, for example with a somewhat more complex behavior of dark matter than the simple hypothesis of totally inert 'cold dark matter