Galaxy clusters
Other Astronomical Objects
Galaxies are social entities; they rarely appear alone. Since galaxies possess enormous masses—consisting of stars, gas, and dark matter—they attract one another through gravitational forces, forming groups and clusters.
While the universe has been expanding since the Big Bang, gravity within groups and clusters is strong enough to hold them together. Smaller galaxy groups attract additional galaxies, grow, and—over long periods—merge to form large galaxy clusters.
Dark matter is an invisible form of matter in the universe that neither emits nor reflects light. It is not directly visible, but it makes itself known through its gravitational force. Without dark matter, galaxies would fly apart, as it acts like an invisible "glue" that holds the stars together.
Further information on galaxy clusters:
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Ingredients:
Galaxy clusters consist of galaxies (of various types, such as spiral, elliptical, or irregular galaxies), hot gas (the intracluster medium, which often emits X-rays), and dark matter, which accounts for the majority of the mass and stabilizes the structure.
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Size and Mass:
Sie erstrecken sich über Millionen von Lichtjahren und haben typischerweise eine Masse von etwa 10^{14} bis 10^{15} Sonnenmassen.
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Entstehung:
Galaxy clusters form through the gravitational attraction of smaller groups of galaxies and matter over billions of years. They are part of the large-scale structure of the universe, which forms a network of filaments, walls, and voids.
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Examples:
Well-known galaxy clusters are the Virgo Cluster (approximately 54 million light-years away; contains our Milky Way) and the Coma Cluster.
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Meaning:
They are important for cosmology, as they provide clues regarding the distribution of matter, the expansion of the universe, and the role of dark matter and dark energy.
Link to Wikipedia: Galaxiy Cluster
Link to Wikipedia: Virgo Cluster
Link to Wikipedia: Abell catalogue
