Galaxy clusters much more common than thought

Data mining exercise reveals a whole new class of astronomical structure. Andrew Masterson reports.

Bright galaxy clusters on dark background
Galaxy clusters are enormous collections of hundreds or thousands of galaxies and vast reservoirs of hot gas embedded in massive clouds of dark matter. These images contain X-ray data from Chandra (blue), optical light from Hubble (red, green, and blue), and radio data from the Very Large Array (pink).