NGC 4618 and NGC 4625

NGC 4618 (left) is a large, one-armed spiral galaxy located in the constellation Canes Venatici. The smaller, compact-looking galaxy to the right is NGC 4625. In this visible light image, spiral arms are very difficult to see, which originally led astronomers to believe it was a fairly plain and old galaxy. Back in 2005, NASA's Galaxy Evolution Explorer imaged NGC 4618 with a combination of visible and ultra-violet light. The resulting image showed bright spiral arms emitting significant ultra-violet light, indicating large amounts of star formation. This stage of galaxy evolution was once thought to only be found in distant galaxies, but NGC 4625 is a mere 31 million lightyears away! Studies of this galaxy could potentially clue astronomers in to how stars were formed within our own Milky Way galaxy. It is hypothesized that a collision with NGC 4618 could have potentially triggered the creation of NGC 4625's spiral arms, although that theory leaves NGC 4618's lack of spiral arms a mystery.

This image was taken as part of Advanced Observing Program (AOP) program at Kitt Peak Visitor Center during 2014.