Dark matter, the invisible material that makes up the overwhelming majority of the universe’s mass, may collect itself to form atoms, a brand new simulation shows.
Those “dark atoms” might radically alter the evolution of galaxies and the formation of stars, giving astronomers a brand new opportunity to know this mysterious substance.
Dark matter makes up over 80% of the mass of each galaxy and cluster of galaxies in the universe. All of our observations suggest that dark matter is a few latest form of particle, one that doesn’t interact with normal matter and even with light. We will discover dark matter only through its gravitational interactions with every little thing else. Whatever dark matter is, it’s beyond our current understanding of physics. But it surely still has mass, so it still has gravity.
We don’t yet know if dark matter is straightforward or complex. It might be fabricated from just one form of particle that dominates the universe and barely interacts with even itself. Or it could be fabricated from multiple sorts of particles, with as wealthy a range as we see in normal matter. Beyond that, we all know of only 4 fundamental forces of nature: gravity, electromagnetism, the strong nuclear force and the weak nuclear force. But there could also be additional forces that operate only among the many dark matter particles and don’t interfere with normal matter in any respect.
Related: What’s dark matter?
Getting together
The concept of additional dark matter particles and dark forces is not as far-fetched because it could appear. Our understanding of physics is built on symmetries, that are deep mathematical relationships between particles. It could thoroughly be that there are additional symmetries within the laws of nature that make dark matter a twin of normal matter and that, for each form of interaction that ordinary matter can take part in, there may be a counterpart at midnight sector.
For instance, with normal matter, we are able to construct easy atoms: a proton and an electron sure together, with the photon, the carrier of the electromagnetic force, mediating the interaction. We could even have a dark matter version of that very same structure, with a dark proton sure to dark electrons via dark photons: dark atoms.
Atomic dark matter would behave much otherwise than dark matter composed of only a single particle. Most significantly, easy dark matter would have a really difficult time clumping up, only doing so slowly over a whole bunch of hundreds of thousands of years. Normal matter collects in those smooth pools of dark matter to form galaxies, but otherwise, the 2 lead separate lives. Atomic dark matter, nevertheless, could form its own shadowy galaxies — disk-like structures that mimic the dimensions and layout of visible galaxies.
A team of astrophysicists used this intriguing possibility to simulate the evolution of galaxies and see what observable differences might arise. They allowed the atomic dark matter to evolve based on its own forces after which examined how those latest structures would affect visible galaxies through the brand new arrangement of gravity. They published their leads to the net preprint database arXiv in April.
Related: If dark matter is ‘invisible,’ how will we realize it exists?
Stellar sabotage
The researchers found that even a small amount of atomic dark matter — as little as 6% of all of the dark matter within the universe, leaving the remaining to be easy — was enough to radically alter the evolution of galaxies. Since the atomic dark matter could interact, it could easily clump together by losing energy through the emission of some type of dark radiation. The simulations revealed that a “dark disk” quickly appeared inside each galaxy, with the spin of the disk closely matching that of the visible, normal components.
From there, the atomic dark matter continued to clump, identical to normal gas clumps into clouds and, eventually, stars. Within the simulation, the atomic dark matter formed dark stars of its own and will even trigger the formation of its own black holes. Those clumps then sank into the core of the galaxy, where the density increased.
With all that extra gravity, star formation within the cores of galaxies kicked into overdrive, producing stars at a much faster rate than in galaxies with easy dark matter. These simulations actually ruled out some models of atomic dark matter, because those models caused their galaxies to expire of recent material for making stars far too quickly.
But some models survived current observational limits, allowing for the continued possibility of atomic dark matter. The researchers hope that further theoretical and experimental studies will make clear the plausibility of this intriguing type of exotic matter. For instance, because atomic dark matter clumps so efficiently, we’d have the ability to identify dense, star-like clumps with upcoming gravitational microlensing studies with NASA’s Nancy Grace Roman Space Telescope.