A triplet of interacting galaxies, or maybe not?

Since its discovery, it has been assumed that this system, known as Arp 248, consists of three interacting galaxies. Recent observations of the Hubble Space Telescope have indicated that this may not be the case.

Let’s start from the beginning. Arp 248, also known as the Wild Triplet after its discoverer, is a system of interacting galaxies located 200 million light years from Earth, visible in the constellation of Virgo. The system consists of two large spiral galaxies connected by a 200,000-light-year-long tidal bridge and a smaller galaxy seen almost cut between these two.

There is no doubt that the two galaxies on either side of the image are interacting. The tidal bridge in fact indicates that stars and gas are being torn away due to mutual gravitational interactions. The two galaxies as a result will collide and merge into one giant spiral galaxy.

It was thought that the third central galaxy interacted with the other two, although no bridge of connection was observed between them. However, recent Hubble studies have allowed us to more accurately determine the distances of the three galaxies and this has allowed us to discover how in truth the central galaxy is much more distant than the other two and seems to be part of the system only for a pure effect prospective.

Credit: ESA/Hubble, NASA, Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA, J. Dalcanton.