Hubble presents six magnificent galaxy mergers

It is during rare fusion events that galaxies undergo dramatic changes in their appearance and stellar content. These systems are excellent laboratories for tracking the formation of star clusters under extreme physical conditions.

The Milky Way generally forms clusters of stars whose masses are 10,000 times the mass of our Sun. It doesn’t compare to the masses of star clusters that form in colliding galaxies, which can be millions of times the mass of our Sun.

These dense star systems are also very bright. Even after the collision, when the resulting galactic system begins to merge into a calmer phase, these very massive star clusters will shine throughout their host galaxy, as enduring witnesses to past fusion events.

By studying the six galaxy mergers presented here, the Hubble Imaging Probe of Extreme Environments and Clusters (HiPEEC) survey investigated how star clusters are affected in collisions by the rapid changes that dramatically increase the rate at which new stars form in these galaxies. Hubble’s capabilities have made it possible to resolve large star-forming “nodes” into many young, compact star clusters. Hubble’s ultraviolet and near infrared observations from these systems were used to derive the ages, masses and extinctions of star clusters and to analyze the rate of star formation in these six molten galaxies.

The HiPEEC study reveals that the populations of star clusters undergo large and rapid variations in their properties, the most massive clusters being formed towards the end of the fusion phase.