Galaxy Cluster
A gravitationally bound structure containing hundreds to thousands of individual galaxies bound together by gravity.
Governing formula
M_total ~ 10¹⁴–10¹⁵ M_☉ (80% Dark Matter, 15% Intracluster Gas, 5% Stars)
SI unit
Megaparsecs (Mpc) & M_☉
In depth
Galaxy clusters are the largest gravitationally bound structures in the universe. Most baryonic mass resides in hot X-ray emitting intracluster medium gas (T ~ 10⁷–10⁸ K), while dark matter dominates total gravitational mass.
Examples in the real world
The Coma Cluster (Abell 1656) containing over 1,000 identified galaxies ~320 million light-years away.