Knowra Galaxy group Galaxy group A gravitationally bound collection of galaxies, typically smaller and less massive than a galaxy cluster. Its members orbit within a shared dark-matter halo.
Galaxy : A gravitationally bound system of stars, stellar remnants, gas, dust, and dark matter. Each group is assembled from galaxies such as the Milky Way.
Dynamical friction : A drag on a massive object moving through a background of particles, caused by its gravitational wake. It can slow group galaxies and help them sink toward the group's center.
Local Group : The galaxy group that contains the Milky Way, the Andromeda Galaxy, and dozens of smaller galaxies. It is the nearest example and establishes the setting of the Milky Way.
Galaxy group catalog : A compiled list of galaxy groups identified from astronomical observations or simulations. Catalogs let astronomers compare group populations across the sky and cosmic time.
Large-scale structure of the universe : The cosmic arrangement of matter into galaxies, groups, clusters, filaments, and voids. Groups form as dense nodes within this larger distribution.
Dark matter halo : A region of dark matter whose gravity shapes the motion and structure of galaxies. Its gravity supplies most of the mass binding a group.
Galaxy merger : The collision and eventual gravitational coalescence of two or more galaxies. Frequent encounters in groups can drive mergers and reshape member galaxies.
M81 Group : A nearby galaxy group centered on the spiral galaxy Messier 81. Its interacting galaxies show how group gravity can produce tidal structure.
Friends-of-friends algorithm : A method that links nearby data points into sets using a chosen linking distance. It identifies candidate groups by linking galaxies close in position and velocity.
Cosmic web : The network of matter in the universe, organized into filaments, sheets, and voids. Filaments funnel galaxies and dark matter into groups.
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