HCG 86, the quartet of galaxies identified by a Frederick study

It comes from a study, published in Astronomy & Astrophysics, led by Ph.D. student Rossella Ragusa of the Frederick Department of Physics, in collaboration with theNational Institute of Astrophysics, the image of the week from the European Southern Observatory (ESO), Europe's reference body for optical astronomy in Europe.

It is the group of four galaxies, HCG 86, about 270 million light-years from Earth in the constellation Sagittarius and arranged in a triangular shape, with three of them in a straight line and one to the south, immortalized by the VLT Survey Telescope (VST) located at the Eso Observatory in Paranal, Chile, among the world's largest survey telescopes dedicated to mapping the sky in visible light wavelengths.

HCG stands for Hickson Compact Group and is used to describe groups of four to ten galaxies in which the members are physically very close to each other. Because of their compactness, such groups are ideal environments for studying galactic interactions, which can sometimes lead to galaxies merging with each other.

"With VST we are able to investigate very faint structures in the periphery of galaxies, which are relics of past gravitational interactions and merger events," Ragusa says.

In particular, by mapping the distribution of light in and around the group's galaxies in this study, the team concluded that these faint structures are the remnants of satellite galaxies devoured by the group some seven billion years ago.