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This image combines data from four different space telescopes to create a multi-wavelength view of all that remains of the oldest documented example of a supernova, called RCW 86. The Chinese witnessed the event in 185 AD, documenting a mysterious "guest star" that remained in the sky for eight months. X-ray images from the European Space Agency's XMM-Newton Observatory and NASA's Chandra X-ray Observatory are combined to form the blue and green colors in the image. The X-rays show the interstellar gas that has been heated to millions of degrees by the passage of the shock wave from the supernova. Infrared data from NASA's Spitzer Space Telescope, as well as NASA's Wide-Field Infrared Survey Explorer (WISE) are shown in yellow and red, and reveal dust radiating at a temperature of several hundred degrees below zero, warm by comparison to normal dust in our Milky Way galaxy. By studying the X-ray and infrared data together, astronomers were able to determine that the cause of the explosion witnessed nearly 2, 000 years ago was a Type Ia supernova, in which an otherwise-stable white dwarf, or dead star, was pushed beyond the brink of stability when a companion star dumped material onto it. RCW 86 is approximately 8, 000 light-years away. At about 85 light-years in diameter, it occupies a region of the sky in the southern constellation of Circinus that is slightly larger than the full moon.
