NGC 6240 is a peculiar, butterfly- or lobster-shaped galaxy consisting of two smaller merging galaxies. It lies in the constellation of Ophiuchus, the Serpent Holder, some 400 million light-years away. Observations with NASA's Chandra X-ray Observatory have disclosed two giant black holes, about 3,000 light-years apart, which will drift toward one another and eventually merge together into a larger black hole. The merging process triggered dramatic star formation and sparked numerous supernova explosions. The merger will be complete in some tens to hundreds of millions of years.
This image is part of a large collection of 59 images of merging galaxies taken by the Hubble Space Telescope and released on the occasion of its 18th anniversary on 24th April 2008.
Image Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)
Explanation from: https://www.spacetelescope.org/images/heic0810ai/