One of many large mysteries about darkish matter particles is whether or not they work together with one another. We nonetheless don’t know the precise nature of what darkish matter is. Some fashions argue that darkish matter solely interacts gravitationally, however many extra posit that darkish matter particles can collide with one another, clump collectively, and even decay into particles we are able to see. If that’s the case, then objects with significantly robust gravitational fields akin to black holes, neutron stars, and white dwarfs would possibly seize and focus darkish matter. This might in flip have an effect on how these objects seem. As a living proof, a current examine seems to be on the interaction between darkish matter and neutron stars.
Neutron stars are fabricated from probably the most dense matter within the cosmos. Their highly effective gravitational fields might lure darkish matter and in contrast to black holes, any radiation from darkish matter gained’t be trapped behind an occasion horizon. So neutron stars are an ideal candidate for learning darkish matter fashions. For this examine, the group checked out how a lot darkish matter a neutron star might seize, and the way the decay of interacting darkish matter particles would have an effect on its temperature.
The main points rely upon which particular darkish matter mannequin you employ. Quite than addressing variant fashions, the group checked out broad properties. Particularly, they targeted on how darkish matter and baryons (protons and neutrons) would possibly work together, and whether or not that may trigger darkish matter to be trapped. Positive sufficient, for the vary of doable baryon-dark matter interactions, neutron stars can seize darkish matter.
The group then went on to have a look at how darkish matter thermalization might happen. In different phrases, as darkish matter is captured it ought to launch warmth vitality into the neutron star via collisions and darkish matter annihilation. Over time the darkish matter and neutron star ought to attain a thermal equilibrium. The speed at which this happens will depend on how strongly particles work together, the so-called scattering cross-section. The group discovered that thermal equilibrium is reached pretty rapidly. For easy scalar fashions of darkish matter, equilibrium may be reached inside 10,000 years. For vector fashions of darkish matter, equilibrium can occur in only a yr. Whatever the mannequin, neutron stars can attain thermal equilibrium in a cosmic blink of a watch.
If this mannequin is appropriate, then darkish matter might play a measurable function within the evolution of neutron stars. We might, for instance, establish the presence of darkish matter by observing neutron stars which might be hotter than anticipated. Or even perhaps distinguish totally different darkish matter fashions by the general spectrum of neutron stars.
Reference: Bell, Nicole F., et al. “Thermalization and annihilation of dark matter in neutron stars.” Journal of Cosmology and Astroparticle Physics 2024.04 (2024): 006.
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