M81 in True Color
Here's what a spiral galaxy REALLY looks like. Yesterday, M81 was shown in two colors only, but here we see M81 at its most colorful . In the above picture , note how blue the spiral arms are - this indicates the presence of hot young stars and on-going star formation . Also note the yellow hue of the nucleus, possibly designating a population of older stars many billions of years old. M81 is actually a dominant member of a group of galaxies which includes M82 and several other galaxies. Unlike our Local Group of galaxies, large galaxies in the M81 group are actually colliding . It is possible that M81's interaction with M82 create the density waves which generate M81's spiral structure.