In the upper left is the spiral galaxy M81, surrounded by blue arms and decorated with reddish nebulae. At the bottom right is M82, an irregular galaxy with a bright streak running through its center and surrounded by red gas. This impressive image reflects the gravitational struggle between two massive galaxies that has been going on for nearly a billion years.

These galaxies come close to each other about every hundred million years, strongly influencing each other. During the last close passage, M82's gravity created density waves around M81, which shaped the distinctive structure of M81's arms today. At the same time, M81's influence triggered violent star formation in M82, while colliding gas clouds created energetic regions that emitted X-rays.

From the Milky Way Galaxy, this celestial encounter can be seen through a faint “Integrated Changing Nebula” of gas and dust, of which little is still known. In the next few billion years, these two galaxies are expected to merge, leaving only one galaxy.

May 7, 2025 Astronomy Photo of the Day (NASA APOD)

Image Source and Copyright: Collaborative Astrophotography Team (CAT)