Kepler's Supernova Remnant in 60 Seconds

Narrator (April Hobart, CXC): Over 400 years ago, Johannes Kepler and many others witnessed the appearance of a new "star" in the sky. Today, this object is known as the Kepler supernova remnant. For some time, astronomers have thought that the Kepler remnant comes from a so-called Type Ia supernova. These supernovas are the result of a thermonuclear explosion of a white dwarf. However, there is an ongoing controversy about Type Ia supernovas. Are they caused by a white dwarf pulling so much material from a companion star that it becomes unstable and explodes? Or do they result from the merger of two white dwarfs? New Chandra images reveal a disk-shaped structure near the center of the remnant. Researchers interpret this X-ray emission to be caused by the collision between supernova debris and disk-shaped material that a giant star expelled before the explosion. This and other pieces of evidence suggest that at least the Type Ia explosion that created Kepler was not the result of a merger between white dwarfs. Since these supernovas are used to measure the expansion of the Universe itself, astronomers are eager to understand them inside and out.