A galactic cluster is a gravitationally bound system of galaxies. It contains hundreds to thousands of galaxies, held together by their mutual gravitational attraction.

Elliptical galaxies are the most common type of galaxy found in galactic clusters. They are characterized by their smooth, round or elliptical shape and lack of prominent spiral arms.

Abell 2218 is the largest known galactic cluster, containing thousands of galaxies. It is located about 2.7 billion light-years away from Earth.

The intracluster medium is the hot gas that fills the space between galaxies in a cluster. It is composed of hydrogen and helium, and can reach temperatures of millions of degrees Celsius.

Dark matter plays a significant role in galactic clusters. It helps to hold the galaxies together, provides the energy needed to heat the intracluster medium, and shapes the distribution of galaxies within the cluster.

Studying galactic clusters provides valuable insights into the formation and evolution of galaxies, helps us understand the large-scale structure of the universe, and allows us to measure the Hubble constant.

Galactic clusters are larger, contain more galaxies, and are more densely packed than groups of galaxies.

The typical mass of a galactic cluster is around 10^14 solar masses.

The typical size of a galactic cluster is around 10 million light-years.

The typical number of galaxies in a galactic cluster is around 1,000.

The typical temperature of the intracluster medium is around 10^8 K.

The typical density of the intracluster medium is around 10^-3 atoms/cm^3.

The typical X-ray luminosity of a galactic cluster is around 10^44 erg/s.

The typical radio luminosity of a galactic cluster is around 10^43 erg/s.