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17.7: Key Terms

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    Evolution of Galaxies Key Terms

    • cold dark matter: slow-moving massive particles, not yet identified, that don't absorb, emit, or reflect light or other electromagnetic radiation
    • cosmological principle: the assumption that, on the large scale, the universe at any given time is the same everywhere—isotropic and homogeneous
    • dark energy: an energy that is causing the expansion of the universe to accelerate; the source of this energy is not yet understood
    • evolution (of galaxies): changes in individual galaxies over cosmic time, inferred by observing snapshots of many different galaxies at different times in their lives
    • galactic cannibalism: a process by which a larger galaxy strips material from or completely swallows a smaller one
    • homogeneous: having a consistent and even distribution of matter that is the same everywhere
    • hot dark matter: massive particles, not yet identified, that don't absorb, emit, or reflect light or other electromagnetic radiation; hot dark matter is faster-moving material than cold dark matter
    • isotropic: the same in all directions
    • Local Group: a small cluster of galaxies to which our Galaxy belongs
    • merger: a collision between galaxies (of roughly comparable size) that combine to form a single new structure
    • quasar: a distant, point-like energy source originating from a powerful active galactic nucleus. Its luminosity is generated by the accretion of gas onto a supermassive black hole
    • starburst: a galaxy or merger of multiple galaxies that turns gas into stars much faster than usual
    • supercluster: a large region of space (more than 100 million light-years across) where groups and clusters of galaxies are more concentrated; a cluster of clusters of galaxies
    • void: a region between clusters and superclusters of galaxies that appears relatively empty of galaxies

    17.7: Key Terms is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by LibreTexts.

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