Could dark matter explain Milky Way’s missing satellite galaxies?
Why the Milky Way has so few satellite galaxies could be all down to the elusive dark matter, say European astronomers.
An artist’s impression of the Milky Way galaxy
The reason behind why the Milky Way has so few satellite galaxies could be all down to the elusive dark matter, according to a team of European astronomers.
Our galaxy’s lack of galactic minions has left experts questioning the widely accepted theory of cold dark matter, which is said to allow for more galaxy formation than seen today.
Computer simulations chronicling the stages of formation of our home galaxy were carried out by the joint efforts of a team of cosmologists and particle physicists from Durham University and LAPTh College & University in France. The collaboration of scientists believe that the behaviour of dark matter could be a potential solution to the problem.
“By using computer simulations to allow the dark matter a little more interactive with the rest of the material in the universe, such as photons, we can give our cosmic neighbourhood a makeover and we see a remarkable reduction in the number of galaxies around us compared with what we originally thought,” explains Carlton Baugh, co-author of a paper published in the journal Monthly Notices of the Royal Astronomical Society (MNRAS).
Two models of the dark matter distribution in the halo of a galaxy like the Milky Way, separated by a white line. The left shows how non-interacting cold dark matter produces an abundance of smaller satellite galaxies. The right illustrates the interaction of dark matter with other particles to reduce the number of satellite galaxies we expect to observe around the Milky Way
Baugh and his colleagues think that clumps of dark matter, which hailed from a younger universe might have held the intergalactic gas – needed to build stars and galaxies – hostage. Further more, the scattering of the elusive dark matter particles by the likes of photons or neutrinos is likely to have wiped out the structures holding onto this gas, killing any chance of satellite galaxies being made.
“By tuning the strength of the scattering particles, we change the number of small galaxies, which lets us learn more about the physics of dark matter and how it might interact with other particles in the universe,” says lead scientist Celine Boehm of Durham University on the workings of the computer simulation, which is powered by Durham’s COSMA supercomputer.
“Astronomers have long since reached the conclusion that most of the matter in the universe consists of dark matter,” concludes Baugh. “This model can explain how most of the universe looks, except in our own backyard where it fails miserably!”
All About Space is available every month for just £3.99! Alternatively you can subscribe here for a fraction of the price!