How much of the universe is dark matter
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The Proportion of Dark Matter in the Universe
Overview of Dark Matter Composition
Dark matter constitutes a significant portion of the universe's mass. Current estimates suggest that approximately 25% of the universe's mass is made up of dark matter 234. This non-luminous matter does not emit, absorb, or reflect light, making it invisible and detectable only through its gravitational effects on visible matter.
Observational Evidence and Distribution
Large-Scale Observations
On the largest scales, such as galaxy clusters and superclusters, dark matter can account for up to 99% of the total mass . This is inferred from various observations, including the rotation curves of galaxies, gravitational lensing, and the distribution of hot gas in clusters . These methods consistently show that the visible matter we can observe directly is only a small fraction of the total mass.
Smaller-Scale Observations
In smaller scales, such as within individual galaxies, dark matter still plays a dominant role but to a lesser extent. For instance, dark halos surrounding galaxies contain 10 to 20 times more mass than the luminous stars and cold gas within those galaxies . This indicates that even on smaller scales, dark matter is a crucial component of the universe's mass.
Dark Matter and Cosmic Structure
Dark matter is not only abundant but also essential for the formation and evolution of cosmic structures. It is six times more abundant than ordinary matter and has controlled the growth of structures in the universe . This dominance is crucial for understanding the large-scale structure of the cosmos, including the formation of galaxies and clusters.
Challenges in Direct Detection
Despite its significant presence, dark matter has so far evaded direct detection. Various experiments have been conducted to detect dark matter particles, such as WIMPs (Weakly Interacting Massive Particles) and axions, but none have yet succeeded 710. Indirect detection methods, such as searching for the products of dark matter particle annihilation or decay, are also being actively pursued .
Conclusion
In summary, dark matter constitutes about 25% of the universe's mass and is a critical component in the formation and structure of the cosmos. While it remains undetectable through direct means, its gravitational effects provide compelling evidence of its existence and abundance. Understanding dark matter continues to be one of the most significant challenges in modern astrophysics and cosmology.
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