There is a large spherical area made up of dark matter particles in the centre of spiral galaxies — both those close to us and those billions of light-years away. Dark stars, strange objects in the sky are also made up of this Dark matter
This raises the question on what exactly does “Dark matter” mean and what is the information we currently have on it. In simple terms, Dark matter is a hypothetical form of matter which composites 85% of the observable universe.
Dark matter was first theorized by James Peebles when he published his theory “Cold Dark Matter” in 1982. This theory was published at the same time the “Warm Dark Matter” theory that was published by J. Richard Bond and his team.
The formation of the structure of Dark matter (in accordance with the cold dark matter theory) grows hierarchically, with tiny objects collapsing under their self-gravity and then merging continuously to form larger and more massive objects. The predictions of the cold dark matter theory are accurate as they agree with observations of cosmically large structures.
The reason for choosing the cold dark matter theory over the warm dark matter theory was because of its relevance and accuracy. The cold dark matter theory is more preferred by scientists and has become popular in late 1980s or 1990s. The hot dark matter theory was more popular in the early 1980s.
Dark matter is detected through its gravitational interactions with regular matter and radiation. As a result, determining the elements of cold dark matter is extremely challenging. The candidates that make up Dark matter fall into 3 categories.
Axions are extremely light particles with a unique sort of self-interaction that makes them a good candidate for the CDM. Although axion particles offer the theoretical benefit of solving the strong CP problem in quantum chromodynamics, they have only been postulated and never found. Axions are a kind of WISP (weakly interacting “slender” or “slim” particle), which are the low-mass equivalents of WIMPs.
Massive compact halo objects (MACHOs), which are enormous, dense objects like black holes, neutron stars, white dwarfs, very dim stars, or non-luminous objects like planets. The hunt for these objects involves detecting the influence of these objects on background galaxies through gravitational lensing. The limits imposed by those searches, according to most experts, rule out MACHOs as a possible candidate for dark matter.
Massive particles with weak interactions (WIMPs). Although no particle with the requisite qualities has yet been discovered, numerous extensions of the standard model of particle physics anticipate them. Attempts to directly detect WIMPs with very sensitive detectors, as well as attempts to produce WIMPs with particle accelerators, are all part of the quest for WIMPs. WIMPs are widely considered to be one of the most promising options for dark matter composition. Many scientists are suspicious about the DAMA/NaI experiment and its successor, DAMA/LIBRA, which claim to have directly observed dark matter particles travelling through the Earth. No results from similar experiments appear to be compatible with the DAMA results.
Dark matter is quite a fascinating concept to learn about. We still don’t know for sure about its composition as this is a theory, but we always are making more discoveries in these mysterious topics, more than ever. This always leads us closer to the answer we’re hoping for. I hope all of you have more knowledge on this topic, as I tried my best to break it down. Thank you for reading!