#aglomeradodegalaxia

[wonders-of-the-cosmos]

Galactic treasure chest RXC J0142.9+4438

Galaxies abound in this spectacular Hubble image; spiral arms swirl in all colours and orientations, and fuzzy ellipticals can be seen speckled across the frame as softly glowing smudges on the sky. Each visible speck of a galaxy is home to countless stars. A few stars closer to home shine brightly in the foreground, while a massive galaxy cluster nestles at the very centre of the image; an immense collection of maybe thousands of galaxies, all held together by the relentless force of gravity. ESA/Hubble & NASA, RELICS

[wonders-of-the-cosmos]

This rich galaxy cluster, catalogued as CL0024+17, is allowing astronomers to probe the distribution of dark matter in space. The blue streaks near the center of the image are the smeared images of very distant galaxies that are not part of the cluster. The distant galaxies appear distorted because their light is being bent and magnified by the powerful gravity of CL0024+17, an effect called gravitational lensing. Dark matter cannot be seen because it does not shine or reflect light. Astronomers can only detect its influence by how its gravity affects light. By mapping the distorted light created by gravitational lensing, astronomers can trace how dark matter is distributed in the cluster. While mapping the dark matter, astronomers found a dark-matter ring near the cluster's center. The ring's discovery is among the strongest evidence that dark matter exists. The Hubble observations were taken in November 2004 by the Advanced Camera for Surveys.

Credit: NASA, ESA, M.J. Jee and H. Ford (Johns Hopkins University)

[wonders-of-the-cosmos]

A galaxy cluster, or cluster of galaxies, is a structure that consists of anywhere from hundreds to thousands of galaxies that are bound together by gravity. They are the largest known gravitationally bound structures in the universe and were believed to be the largest known structures in the universe until the 1980s, when superclusters were discovered. One of the key features of clusters is the intracluster medium (ICM). The ICM consists of heated gas between the galaxies and has a peak temperature between 2–15 keV that is dependent on the total mass of the cluster. Galaxy clusters should not be confused with star clusters, such as open clusters, which are structures of stars within galaxies, or with globular clusters, which typically orbit galaxies. Small aggregates of galaxies are referred to as galaxy group rather than clusters of galaxies. The galaxy groups and clusters can themselves cluster together to form superclusters. source

[wonders-of-the-cosmos]

Abell 2744: Pandora's Cluster of Galaxies 

Image Credit: NASA, ESA, J. Merten (ITA, AOB), & D. Coe (STScI)