Dark matter is believed to make up for most of the matter in the universe and yet we know very little about it. What we have discovered is mostly through indirect methods, and now thanks to one of those, a new theory for dark matter has been put in question.
A few months ago, a group of researchers suggested that dark matter might be “fuzzy”. They claimed that it was made by such small particles, 10 trillion times smaller than the mass of an electron, that the quantum mechanical properties would play a crucial role. These fuzzy dark matter particles could interact with each other over thousands of light years.
But new simulations based on intergalactic gas don’t support the idea that fuzzy dark matter can account for all the dark matter. According to the study published in Physical Review Letters, the currently accepted model, known as cold dark matter, is still the best at explaining what we see in the universe.
"For decades, theoretical physicists have tried to understand the properties of the particles and forces that must make up dark matter," lead author Vid Iršič, from the University of Washington, said in a statement. "What we have done is place constraints on what dark matter could be – and 'fuzzy dark matter,' if it were to make up all of dark matter, is not consistent with our data."
Cold dark matter is expected to be made up of weakly interacting massive particles (WIMPs), slowly moving across space. They don’t interact with light and only interact with gravity. The estimated properties of cold dark matter have been used in several models to successfully predict properties of the universe, but it has also some drawbacks. For example, models suggest that the Milky Way should be surrounded by hundreds of small satellite galaxies, while in reality there are only a few dozen. Also, we are yet to detect a single WIMP, although many experiments are currently looking for them.
Fuzzy dark matter solves some of the cold dark matter issues, so Iršič and his colleagues used a supercomputer to see how the distribution of intergalactic gas would be affected in the fuzzy scenario. If most dark matter is as light as the fuzzy hypothesis expects it to be, then the stuff between galaxies should be distributed in a different way.
"The mass of this particle has to be larger than what people had originally expected, based on the fuzzy dark matter solutions for issues surrounding our galaxy and others," added Iršič.
Dark matter continues to remain a mystery, and hopefully we’ll get some answers soon.