Hubble Space Telescope: Kepler's supernova remnant (close-up, visible-light data)

Four hundred years ago a "new star" appeared in the western sky, rivaling the brilliance of the nearby planets. In fact this 'new star' was a supernova, now named Kepler's supernova, and was the last such object seen to explode in our Milky Way galaxy. Seen here are some of its remains.

This image was taken with Hubble's Advanced Camera for Surveys (ACS) with filters onboard to isolate visible light emitted by hydrogen, nitrogen, and oxygen in the remnant but let through starlight from foreground and background stars. The image reveals in Kepler's supernova remnant the detailed knots, which are dense clumps that form behind the outward moving shock wave, and filamentary ribbons, which reveal where the shock wave is encountering lower-density, more uniform interstellar material.