Where do most of the elements essential for life on Earth come from? The answer: inside the furnaces of stars and the explosions that mark the end of some stars' lives. Astronomers have long studied exploded stars and their remains — known as "supernova remnants" — to better understand exactly how stars produce and then disseminate many of the elements on Earth and throughout the cosmos. Cassiopeia A, or Cas A for short, is one of the most intensely studied of these supernova remnants. A new image from NASA's Chandra X-ray Observatory shows the location of different elements in the remains of the explosion: silicon, sulfur, calcium, and iron. Each of these elements produces X-rays within narrow energy ranges, allowing maps of their location to be created. Astronomers also see the blast wave from the explosion in the form of the blue outer ring. X-ray telescopes such as Chandra are important to study supernova remnants and the elements they produce because these events generate extremely high temperatures — millions of degrees — that remain even thousands of years after the explosion. This means that many supernova remnants, including Cas A, glow most strongly at X-ray wavelengths that are undetectable with other types of telescopes. Chandra's sharp X-ray vision helps astronomers not only determine what elements are present in Cas A, but also how much of each there is. For example, Cas A has dispersed about 10,000 Earth masses worth of sulfur alone, and about 20,000 Earth masses of silicon. The iron in Cas A weighs about 70,000 times that of the Earth, and astronomers detect a whopping one million Earth masses worth of oxygen being ejected into space from Cas A, equivalent to about three times the mass of the Sun. Chandra has repeatedly observed Cas A since the telescope was launched into space in 1999. It will continue to do so, revealing new information about the dense core left behind in the center of Cas A, details of the powerful explosion, and specifics of how the important debris is ejected into space.
