An image captured by the Hubble Space Telescope shows a trio of interacting galaxies. Cataloged as SDSSCGB 10189, the trio is a rare case of three massive, star-forming galaxies less than 50,000 light-years apart. At a galactic level, that’s a very short distance, and that’s why their shape is already distorting.

Galaxy mergers are an important topic of astronomical research and in this case, SDSSCGB 10189 is also an object of study for research on the origins of the so-called Brightest Cluster Galaxies (BCGs), the brightest within their clusters and also the most massive.

The Hubble Space Telescope’s Advanced Camera for Surveys (ACS), with two optical frequency filters, and Wide Field Camera 3 (WFC3), with an ultraviolet filter, were used for this observation of SDSSCGB 10189. Mergers between two galaxies are considered normal and many cases in different phases are known and studied by astronomers. However, an interaction between three massive galaxies is a rare and therefore particularly interesting case.

From Earth, we see this trio, cataloged as SDSSCGB 10189, still in an early stage where it’s possible to distinguish the three galaxies involved in the merger. They are less than 50,000 light-years away from each other and for this reason, the gravity of each of them is already affecting its neighbors. Strains of gas and dust have already started being torn away from their galaxies and their progressive approach will increase the distortion of their shapes.

Brightest Cluster Galaxies are the brightest within their clusters and also the most massive, behemoths even by galactic standards. Astronomers suspect that these behemoths form after the merger of massive, gas-rich galaxies. The galaxies of the trio SDSSCGB 10189 are of that type, so the study of their interaction is interesting from various points of view.

It takes millions of years for two or more galaxies to complete a merger. Over that long period, their shapes distort more and more until it’s no longer possible to distinguish the individual galaxies involved in that process. Eventually, a new balance leads to a definitive shape. In the case of the trio SDSSCGB 10189, astronomers have plenty of time to examine the details of the process right from the start.