SCIENTISTS believe they have found a way to explain why there are not as many galaxies orbiting the Milky Way as expected.

Computer simulations of the formation of the galaxy suggest that there should be many more, smaller galaxies around the Milky Way than are observed through telescopes.

This has thrown doubt on the generally accepted theory of cold dark matter, a substance that scientists predict should allow for more galaxy formation around the Milky Way than is seen.

Now cosmologists and particle physicists at the Institute for Computational Cosmology (ICC) and the Institute for Particle Physics Phenomenology (IPPP), at Durham University, working with colleagues at LAPTh College & University in France, think they have found a potential solution to the problem.

Writing in the journal Monthly Notices of the Royal Astronomical Society (MNRAS), the scientists suggest that dark matter particles, as well as feeling the force of gravity, could have interacted with photons and neutrinos in the young Universe, causing the dark matter to scatter.

Scientists think clumps of dark matter – or halos – that emerged from the early Universe, trapped the intergalactic gas needed to form stars and galaxies.

Scattering the dark matter particles wipes out the structures that can trap gas, stopping more galaxies from forming around the Milky Way and reducing the number that should exist.

The researchers say their current findings offer an alternative theory and could provide a novel technique to probe interactions between other particles and cold dark matter. The calculations were carried out using the COSMA supercomputer at Durham University.