The Hubble Space Telescope has captured an intriguing image of an interacting galaxy pair known as Arp-Madore 2339-661. This pair of galaxies lies approximately 500 million light years from Earth in the constellation Tucana, interacting gravitationally with one another. They are so close together that some science literature refers to them as a ‘merging group,’ which means that the galaxies are on a course to become a single entity eventually.
In the Hubble image, the large spiral galaxy NGC 3227 is intertwined in a turbulent gravitational dance with its smaller elliptical companion NGC 3226. The two galaxies also referred to as Arp 94, reside relatively close to each other – 50-60 million light-years away in the direction of the constellation Leo, the Lion. NGC 3227 is a Seyfert galaxy, which boasts a supermassive black hole at its center that emits massive amounts of radiation.
NGC 7733, located below and to the right of NGC 7734, is a member of the elliptical galaxy class and contains a supermassive black hole at the center of its bulge. The elliptical galaxy is siphoning gas and dust from its partner NGC 7734, resulting in the spectacular dance of interaction that Hubble has captured.
What makes this image even more unique is the discovery that there are not just two but three galaxies interacting in this group. In addition to NGC 7733 and NGC 7734, which can be seen quite clearly in this image, there is also a knot-like structure within NGC 7733 that appears to be an additional galaxy. The knot has a distinct color compared to NGC 7733 and is obscured by dust. Astronomers have dubbed this additional galaxy NGC 7733N, and they are attempting to determine its nature and whether it is an independent galaxy or just part of NGC 7733.
The NGC 7733N knot is located in the upper spiral arm of NGC 7733 and is visible as a prominent knot-like structure that stands out against the background of NGC 7733. In a blog post, the ESA explains that this type of knot is prevalent in spiral-shaped galaxies. Astronomers have dubbed these knots filaments, and they are an essential feature in the shaping of galaxy arms, as well as providing insight into how a galaxy merges with its neighbors.
The image also reveals that NGC 7733 is a spiral galaxy with bright regions of star formation, interstellar gas clouds, and prominent dust arms that swirl out from the galaxy’s center. The NGC 7733N knot is most likely a tidal stream of gas and dust, which may result from the interaction between NGC 7733 and NGC 7773. Astronomers are presently trying to determine its origin and what role it may play in this cosmic dance. The image was captured by the Hubble Space Telescope, operated jointly by NASA and the European Space Agency. The telescope has logged over three decades in orbit and recently emerged from a severe technical glitch earlier this year.