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Cassiopeia A: Supernova Remnant

Cas A in Context

X-ray image of Cas A
Cassiopeia A, or Cas A is the remnant of a massive star that exploded around three hundred years ago. The material from the explosion is rushing outward at supersonic speeds in excess of ten million miles per hour. As this matter crashes into gas that surrounded the former star, shock waves analogous to awesome sonic booms heat the gas and heat the ejected matter to temperatures in excess of fifty million degrees Celsius. The colors in this picture show the brightness of the X-rays, where yellow reveals the areas with the most intense X-ray emission.

X-ray image of Cas A
Image courtesy Gordon Garmire,
Penn State U & the ACIS Team.
This is the same Chandra/ACIS image of Cas A as the picture above, but this coloring reveals additional information. It shows the temperature of the hot gas in the supernova remnant: red colors correspond to temperatures below approximately 20 million degrees Celsius, and blue colors correspond to temperatures above approximately 30 million degrees Celsius.

The study of remnants of exploded stars, or supernovas, is essential for our understanding of the origin of life on Earth. The cloud of gas and dust that collapsed to form the Sun, Earth and other planets was composed mostly of hydrogen and helium, with a small amount of heavier elements such as carbon, nitrogen, oxygen and iron. The only place where these and other heavy elements necessary for life are made, is deep in the interior of a massive star. There they remain until a catastrophic explosion spreads them throughout space.

About every fifty years in our galaxy, a massive star explodes. The shell of matter thrown off by the supernova creates a bubble of multi-million degree Celsius gas called a supernova remnant. Cas A is a prime example. The hot gas will expand and produce X-rays for thousands of years.

Return to Cassiopeia A (26 Aug 99)