A team of astronomers He studied two neighboring globular clusters, 47 Tucanae and Omega Centauri, looking for signals from dark matter elimination. The searches turned out to be empty, but they weren’t a failure. Non-detection put strict upper limits on the mass of the hypothetical dark matter particle.
Highlighting dark matter
Dark matter makes up about 80% of all mass in the universe, although it is completely invisible. It simply doesn’t interact with the electromagnetic force, and therefore doesn’t glow, reflect, absorb, or anything. So far, the only evidence we have of its existence is through the effects of gravity on the rest of the universe. For this reason, astronomers are not entirely sure what dark matter is, although many physicists believe that it is a new type of particle not previously known to the Standard Model of particle physics.
One possibility is that dark matter is made up of some ultralight particles, such as axons. And although these particles will not interact with ordinary matter, they rarely interact with themselves, smashing together and annihilating. If the collision energy is high enough, it can result in the production of gamma rays, which then split to become an electron and a positron.
These electrons and positrons can stick together to form bound states, called positroniums. However, positronium atoms are not stable, and eventually decay, leaving behind a flash of radio emission.
So even though dark matter does not interact with electromagnetism directly, there is still a possibility that we will see radio emission from the collision and decay of dark matter particles.
Look at the globular clusters
To make this work, you need a lot of dark matter. If dark matter particles collide easily enough, we would have seen them already. So collisions should be rare. The density of dark matter in the galaxy’s vicinity is too low to emit detectable emissions, but the dense cores of galaxies may provide better access.
The normal place we should look is in the heart of our galaxy, but that place is awash in all kinds of radio emissions, so it’s hard to tell if a particular signal is coming from dark matter eradication or something more ordinary. That’s why a team of astronomers looked at two adjacent globular clusters, as reported in a research paper recently published in the preprint journal arXiv.
The two groups, 47 Tucanae and Omega Centauri, are a few thousand light years away, making them relatively easy to observe. Astronomers believe they are the remnants of dwarf galaxies, the bulk of their stars stripped from interactions with the Milky Way.
This makes ideal Labs clusters because they are basically balls of a dense dark matter with little to no contamination. The team of astronomers went looking for the unique radio signal of the decay of positronium using the Parks Observatory in Australia.
They didn’t find anything, which isn’t necessarily a bad thing. Based on their observations, they were able to establish the best upper bounds yet on the mass and cross-section (a measure of how frequently particles interact) for these light-dark matter models. Sure, it was great to see a sure sign and put this dark matter puzzle to the end, but new knowledge in any direction is always welcome and always useful.
This article was originally published universe today by Paul M. Sutter. Read the original article here.
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