One of the most likely candidates for the constituents of dark matter are axions. However, the existence of these particles hasn’t been proven yet. However, scientists hypothesize that the magnetic fields of neutron stars can generate their entire clouds and the events we can observe occur in them.
Axions as constituents of dark matter
Physicists from Amsterdam, Princeton and Oxford may have found a way to confirm the existence of dark matter. They hope that neutron stars and the clouds of exotic particles that form around them will help them.
However, this will probably only be true if dark matter is at least partially composed of axions. These particles are mentioned among the most likely candidates for making up the part of the Universe’s mass we can’t see. However, no one can guarantee that this is the case.
The fact is that scientists in general have never observed dark matter directly. They just know that there must be something else that doesn’t interact or barely interact with protons, neutrons, electrons, photons, and the rest of visible matter, and only gravitational influence tells us that there is something out there in the depths of space, and it’s bigger than what we see.
Scientists invented axions about 50 years ago to explain some weird things about the neutron, and named them after a brand of soap to emphasize that they should “wash away” all the problems. They are the best fit for the role of dark matter particles, if only because they can still interact with ordinary matter, albeit very weakly.
What about neutron stars
The main reason for physicists’ optimism about axions is that they can sometimes turn into photons under the action of electromagnetic fields. And photons are very well observed by scientists. Therefore, these particles should be searched for in the most powerful magnets in the Universe — neutron stars.
Previously, the same team of scientists has already found that neutron stars themselves can be sources of axions. However, then they were interested mainly in the most exotic particles that can overcome the gravitational field of dead suns and fly to us. Now they have chosen to focus on those that remain along with the place where they were born.
Axions can form very dense clouds around neutron stars over millions of years, as described in a new study. They themselves still remain invisible. However, their high concentration in magnetic fields should lead to the appearance of such a number of photons, which we should already notice.
Problems of new theory
The authors of the article haven’t decided definitively what exactly the nature of such an interaction should be. Probably, the transformation of axions into photons runs constantly, and then there should be some constant flux of them from the region around the neutron star. Or perhaps there is an accumulation, and a brief but more intense event. Then we would observe a flare.
So far, any numerous models of axion clouds just aren’t there to say anything concrete about them. In addition, the study focused only around single neutron stars, which in themselves are not the best objects to observe.
It would be much more interesting to see how axion clouds behave in binary systems that host the much more visible neutron stars we call pulsars. However, this question remains unanswered for now.
Provided by phys.org
