It is possible that dark matter holds an even darker secret
Introduction
Researchers are comparing the behavior of hypothesized dark matter with actual galaxies.
Dark Matter and Cold Dark Matter
The prevailing idea regarding dark matter refers to the cold dark matter (CDM) theory, which posits that dark matter is composed of low-velocity particles that do not interact with each other. This belief has been discussed and may be discussed again. A team of researchers from the University of California, Riverside, led by astronomer Hai-Bo Yu, has put forward an alternative idea that explains two extreme cases where cold dark matter does not perform well.
Self-Interacting Dark Matter
Yu and his colleagues instead believe that some dark forces cause dark matter particles to collide with one another. This is known as self-interacting dark matter (SIDM).
Cold Dark Matter and Hot Dark Matter
Dark matter is considered “dark” because its interactions with visible matter and electromagnetic radiation are weak or non-existent. Light cannot illuminate it due to its inability to significantly interact with any kind of electromagnetic radiation. The reason dark matter is considered “cold,” at least according to cold dark matter theory, is that slow-moving particles move at speeds slower than light.
Self-Interacting Dark Matter and Its Interpretation
Believing in the existence of invisible particles that interact either by pushing each other away into a dispersed halo or pulling each other closer into a dense halo allows for new interpretations. But first, why is it overwhelmingly believed that dark matter is cold?
More Light on Self-Interacting Dark Matter
It is being tested whether self-interacting dark matter can explain an aspect of cold dark matter that really does not work: it struggles to explain very dense and widely dispersed dark matter halos.
The Effect of Self-Interacting Dark Matter on Gravitational Lensing
This second scenario deals with very dense dark matter halos that affect gravitational lensing. These dense halos contain enough dark matter to bend spacetime such that light passing through that region of space is also bent. Due to these distortions, the object behind the specific galaxy appears magnified, although often in a somewhat warped manner. Self-interacting dark matter also supports sufficient concentrations of dark matter to affect gravitational lensing because colliding particles must be able to go inward just as they go outward. Increasing the proximity of the particles to each other raises the halo’s density, and their masses can form a massive amount of dark matter that produces gravitational lensing.
Conclusion
We are still in the dark about dark matter in many ways. Until we can directly detect it, we must rely on theoretical work to see if ideas like self-interacting dark matter might have merit. Perhaps one day we will have a direct detection method that will finally unveil the secrets of dark matter.
Source: Astrophysical Journal Letters, 2023. DOI: 10.3847/2041-8213/ad0e09
Source: Elizabeth Rayne
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