What is the 'Ring Galaxy' mentioned by Carl Sagan in an interview?

I suspect he might have been referring to the 'Cartwheel Galaxy'. It is 500 million light years distant in the constellation Sculptor. It was involved in a collision with a smaller galaxy about 200 million years ago, whose direct collision produced the galaxy's ring-like shape. For more information, see the Hubble Space Telescope web site which shows recent dramatic pictures of this galaxy taken by astronomers Curt Struck, Philip Appleton, Kirk Borne and Ray Lucas in 1996.
Copyright 1997 Dr. Sten Odenwald
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