July 26, 1997
The oldest light in the universe still hums faintly through space, a relic of the beginning itself.
M81 in True Color
Birthday · July 26, 1997
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APOD published July 26, 1997. Full image credits are on the original APOD entry below. A publication-date match, not a photo taken on your date. Independent of NASA.
Here's is a spiral galaxy in true colors. Previously, M81 was shown in two colors only, but M81's real colors are just as dramatic. 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, indicating am ancient population of 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.