The debris from a supernova observed in 1604.

This composite image of Kepler’s supernova remnant shows different colors ranging from lower to higher energies: red, yellow, green, blue and purple. An optical image from the Digitized Sky Survey (pale yellow and blue) shows stars in the field. The Kepler supernova was a Type Ia event, the thermonuclear explosion of a white dwarf. New analysis suggests that the supernova explosion was not only more powerful, but might have also occurred at a greater distance, than previously thought.