Two merging galaxies' immense gravity warps their arms into an embrace in a stunning new image from the Hubble Space Telescope.
The galaxy merger, Arp-Madore 417-391, was first described in the Arp-Madore catalog of strange and unusual galaxies and is located about 670 million light-years away, in the Southern Hemisphere constellation Eridanus. What makes this particular galaxy merger so compelling is the force of the two galaxies' gravity twisting and distorting their shapes to form an irregular ring, with the nuclei of the two colliding galaxies left side by side on the bottom left of the structure, Hubble Space Telescope scientists explained in a statement.
Arp-Madore 417-391 is somewhat reminiscent of a different class of galactic structure known as a ring galaxy, the most famous of which is Hoag's object; these ring galaxies make up less than 0.1% of known galaxies. As the name suggests, ring galaxies have a pronounced ring structure rather than the arms of a typical spiral galaxy. Astronomers are still debating how these kinds of galaxies form, but galaxy collisions are considered a likely candidate.
The Hubble Space Telescope snapped the image during its survey of "intriguing targets" meant to identify candidates for more detailed follow-up observations by the James Webb Space Telescope. The Hubble team recently released another such Arp-Madore object, Wild's Triplet, which also shows the gravitational influence of a pair of interacting galaxies, though it's not as dramatic as Arp-Madore 417-391.
To capture the image of Arp-Madore 417-391, Hubble relied on its Advanced Camera for Surveys, which is specifically tailored to hunt for ancient galaxies and galaxy clusters that formed in the early days of the universe. The James Webb Space Telescope is much better suited for this kind of deep-space observation, however, thanks to its sensors that can see much further into the infrared spectrum and, therefore, reveal finer details of galaxies that are even older than Arp-Madore 417-391.
It's too soon to say whether Webb will make a return to Arp-Madore 417-391, but compiling a list of interesting candidates for the advanced space telescope is a necessary first step.