Exploring the Immensity of Galaxy Clusters

Formation & Growth

Galaxy clusters formed through a hierarchical process beginning with smaller groups of galaxies. These groups then merged over billions of years, driven by the mutual gravitational attraction between their constituent members. This process is often referred to as ‘bottom-up’ formation.

Composition & Dark Matter

Clusters are dominated not by galaxies themselves, but by hot, X-ray emitting gas – the intracluster medium (ICM). This ICM makes up roughly 60% of the cluster’s mass. The remaining ~40% is attributed to dark matter, which interacts gravitationally but not through electromagnetic forces, making it invisible.

ρ ≈ M / V³  (Density approximation)

Dynamics & Hubble Diagrams

The velocities of galaxies within a cluster are used to determine its distance. This technique, known as the Faber-Jackson relation, relates a galaxy’s radius to its velocity dispersion – a measure of the random motions of its stars. Clusters also serve as valuable ‘standard rulers’ in cosmology.

v = √(GM/R) (Velocity due to gravity)

Examples & Research

Notable examples include the Coma Cluster and the Bullet Cluster, where observations of gravitational lensing provide strong evidence for dark matter’s existence. Studying clusters helps us understand galaxy formation, evolution, and the nature of dark matter and dark energy.

Frequently asked questions

Try it live

Everything above runs in your browser — open SPH Fluid and change the parameters while it is running. Nothing is installed, nothing is uploaded, the whole model lives in one tab.