Galactic Clusters: Families of Galaxies Bound Together

  1. Galactic clusters are groups of dozens to thousands of galaxies held together by gravity.
  2. The Milky Way belongs to the Local Group, a small cluster of over 50 galaxies.
  3. Giant clusters like the Virgo Cluster contain thousands of galaxies spanning millions of light-years.
  4. Dark matter makes up most of a cluster’s mass, holding it all together.
  5. Hot gas between galaxies in clusters glows in X-rays, outshining the galaxies themselves.
  6. Galaxy clusters often form superclusters—the largest structures in the known universe.
  7. Collisions between galaxies in clusters can spark bursts of star formation.
  8. Gravitational lensing by clusters bends light, magnifying distant galaxies behind them.
  9. Studying clusters helps astronomers understand dark matter and cosmic structure.
  10. Clusters are the “cities” of the universe—where galaxies gather, grow, and evolve.