Credit: NASA/ESA/R. Sankrit and W. Blair (Johns Hopkins University)

This infrared image from NASA's Spitzer Space Telescope shows the expanding remains of a supernova, called Kepler's supernova remnant, first seen 400 years ago by sky watchers, including famous astronomer Johannes Kepler. The supernova remnant is a fast-moving shell of iron-rich material from an exploded star, surrounded by an expanding shock wave that is sweeping up interstellar gas and dust. The image reveals a bubble-shaped shroud of gas and dust that is 14 light-years wide and is expanding at 4 million miles per hour (2,000 kilometers per second).

The Spitzer telescope shows microscopic dust particles that have been heated by the supernova shock wave. The dust re-radiates the shock wave's energy as infrared light.

Kepler's supernova, the last such object seen to explode in our Milky Way galaxy, resides about 13,000 light-years away in the constellation Ophiuchus.

The Spitzer observations were taken in August 2004.