October 24, 2023

Arp-Madore 2339-661 (Image ESA/Hubble & NASA, J. Dalcanton, Dark Energy Survey/DOE/FNAL/NOIRLab/NSF/AURA Acknowledgement: L. Shatz)

An image captured by the Hubble Space Telescope depicts Arp-Madore 2339-661, an object that until not many years ago was considered a pair of interacting galaxies, cataloged as NGC 7733 (bottom right) and NGC 7734 (top left). However, observing the upper arm of NGC 7733, it’s possible to see a sort of large knot of a color different from the predominant blue which is actually a dwarf galaxy, now cataloged as NGC 7733N. The consequence is that the interaction taking place is what some call a merging group. Mergers between two galaxies are normal but sometimes there are more galaxies and in this case, there are three of them that show signs of having active galactic nuclei.