Hubble spies huge clusters of stars formed by ancient encounter

These two views of the heart of the galaxy M82 were snapped by the NASA/ESA Hubble Space Telescope. The image on the left was taken in visible light with the Wide Field and Planetary Camera 2 (WFPC2); the picture on the right, in infrared light. In the infrared view, the telescope's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) peered through thick dust lanes to find some of the galaxy's more than 100 super star clusters. The clusters are the larger white dots scattered throughout the picture. They were formed during a violent encounter with the galaxy M81 about 600 million years ago. The thousands of stars in the galactic background belong to a population of red giant stars in M82. In the lower right corner the full WFPC2 image is shown. The white outline indicates the field of the NICMOS image. The galaxy is 12 million light-years from Earth in the constellation Ursa Major. The NICMOS and WFPC2 pictures were taken on September 15, 1997. Two images each composed of eight exposures were combined for the NICMOS mosaic: 768 seconds in J (1.1 micron - here coloured blue) and 768 seconds in H (1.6 micron - here coloured red) in total. Green is constructed from a mix of J and H. This image is issued jointly by NASA and ESA.