Astronomers Dr Dan Milisavljevic of Harvard-Smithsonian Center for Astrophysics and Dr Robert Fesen of Dartmouth College have generated a three-dimensional map of the interior of the young supernova remnant (SNR) Cassiopeia A, revealing that it is composed of at least six gigantic cavities.
3D reconstruction of SNR Cassiopeia A provides the first detailed look at the distribution of stellar debris following a supernova explosion; the blue-to-red colors correspond to the varying speed of the emitting gas along our line of sight; the background is a Hubble composite image of the remnant. Image credit: Dan Milisavljevic / Robert Fesen / NASA / ESA / Hubble Heritage Team.
To make the map, the scientists examined SNR Cassiopeia A in near-infrared wavelengths of light using the Mayall 4-m telescope at Kitt Peak National Observatory in Tucson, Arizona.
Spectroscopy allowed the team to measure expansion velocities of extremely faint material in the remnant’s interior, which provided the crucial third dimension.
The scientists found that the large interior cavities appear to be connected to – and nicely explain – the previously observed large rings of debris that make up the bright and easily seen outer shell of the remnant.
“Our three-dimensional map is a rare look at the insides of an exploded star,” noted Dr Milisavljevic, who is the lead author of a paper published in the journal Science.
The two most well-defined cavities are 3 and 6 light-years in diameter, and the entire arrangement has a Swiss cheese-like structure.
The bubble-like cavities were likely created by plumes of radioactive nickel-56 generated during the stellar explosion.
Since this nickel will decay to form iron, the team predicts that Cassiopeia A’s interior bubbles should be enriched with as much as a tenth of a solar mass of iron.
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Dan Milisavljevic & Robert A. Fesen. 2015. The bubble-like interior of the core-collapse supernova remnant Cassiopeia A. Science, vol. 347, no. 6221, pp. 526-530; doi: 10.1126/science.1261949
