NASA’s Chandra telescope has taken a series of in-depth observations of Cassiopeia A, a supernova remnant located about 11,000 light-years away. The X-ray telescope was used to work out what elements were produced by the cosmic explosion and what's now being ejected.
The supernova heats up the elements that made up the original star to a whopping 50 million degrees Celsius. This causes the elements to shine brightly, emitting X-ray. Chandra was able to document the distribution of silicon (red), sulfur (yellow), calcium (green), and iron (purple), as well as estimate how much of each element was produced by the star before going supernova. Each of these elements has a characteristic wavelength in X-ray, so astronomers know that what they’re seeing is just those elements.
Cassiopeia A tossed out about 20,000 Earth masses worth of silicon and about 10,000 Earth masses worth of sulfur. It also released enough iron to cast 70,000 Earths made of the metal. Although these numbers are huge for us, none of these elements are by far the most abundant.
The main component of the supernova is oxygen – there is enough oxygen in Cassiopeia A to match the mass of three Suns. Oxygen has an X-ray emission that spans several X-ray wavelengths, so it is not possible to create an “oxygen-only” view of the explosion. Its distribution follows the blast wave as one would expect.
Astronomers have also detected carbon, nitrogen, phosphorus, and of course hydrogen in Cassiopeia A, showing that every element needed to make DNA is there in the supernova remnant. “We are made of star stuff” is not just a saying, the elements in our bodies truly come from dying stars. And all these elements that will one day be making planets, asteroids, and maybe living creatures are currently moving at over 4,000 kilometers (2,500 miles) per second away from the stellar core.
Scientists have not been able to confidently date the explosion, and the general assumption is that its light first reached Earth around the year 1680. The progenitor star of Cassiopeia A is estimated to be 16 times the mass of the Sun, but blew away most of its material during its giant phase. By the time it collapsed on itself and became a supernova, it was only five times the mass of our Sun.