Astronomy Picture of the Day (38 Hours with the M81 Group)
From a garden on planet Earth, 38 hours of exposure with a camera and small telescope produced this cosmic photo of the M81 galaxy group. In fact, the group’s dominant galaxy M81 is near the center of the frame sporting grand spiral arms and a bright yellow core. Also known as Bode’s galaxy, M81 itself spans some 100,000 light-years. Near the top is cigar-shaped irregular galaxy M82.  The pair have been locked in gravitational combat for a billion years. Gravity from each galaxy has profoundly affected the other during a series of cosmic close encounters.  Their last go-round lasted about 100 million years and likely raised density waves rippling around M81, resulting in massive star forming regions arrayed along M81’s spiral arms.  M82 was left with violent star forming regions too, and colliding gas clouds so energetic that the gal