This image was made by combining three CCD frames, taken at the Kitt Peak National Observatory's 0.9-meter telescope in April of 1987. By using different filters in front of the monochrome detector, corresponding approximately to the primary colors red, green and blue, it is possible to recreate a true color picture. Each image was processed to correct for detector sensitivity variations and to remove incorrect regions caused by manufacturing defects and by the arrival of cosmic rays at the telescope.
The dynamic range in this picture has been compressed in order to show both the inner nucleus and the outer structures. In actual fact, the central bright-spot is over 350 times as bright as the faint arc structure visible in the upper right of the picture. In 1991, a supernova went off in the inner ring of NGC3310 near this nucleus.
NGC3310, also known as Arp 217 from its appearance in the Atlas and Catalog of Peculiar Galaxies, is an unusual Sbc galaxy in the constellation of Ursa Major. More than forty-five million light-years from Earth, it is over forty-seven thousand light-years across, when we include the outer low surface brightness areas shown quite effectively in this picture. NGC3310 is sometimes referred to as the 'bow and arrow' galaxy, because of the linear jet-like feature running from near the center towards the upper right of the picture, and crossing a pronounced arc about half-way out. The central region comprises a confused inner ring and a very bright, off-center nucleus, with a second very bright HII region embedded in the ring. The dynamics of this region are chaotic. There is also considerable hydrogen alpha emission throughout this galaxy, indicating active star formation in progress.
NGC3310 has been interpreted both as a violent ejection, causing the inner turmoil and 'squirting' the 'arrow' out across the 'bow', and as a merger remnant, wherein a much smaller system plunged almost directly into the heart of NGC3310, leaving the 'arrow' as a debris trail and disturbing the pre-existing nuclear structure.
