NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) is unraveling the mystery of how stars go supernova by mapping the remnants of radioactive material left in the wake of a supernova. The findings go against previous theories to create a more chaotic view of the conditions prevailing directly before a star explodes.
NuSTAR, launched on 13 June, 2012, represents the first telescope capable of imaging radioactive elements left behind after a supernova. This is achieved by focussing its search to the high energy X-ray (6 -79 KeV) area of the electromagnetic spectrum. Previous telescopes, which hosted coded apertures, were found to be insufficient in observing light in this part of the electromagnetic spectrum.
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The array gathered the new data by observing the remnants of a supernova designated Cassiopeia A, a star which before it went supernova was roughly eight times as large as our Sun. When mapping Cas A the telescope searched for titanium-44, a radioactive isotope which can only be forged in the final stages of a dying star, and therefore the perfect element with which to detect and map a supernova explosion.
"Previously, it was hard to interpret what was going on in Cas A because the material that we could see only glows in X-rays when it's heated up," said Brian Grefenstette of Caltech. "Now that we can see the radioactive material, which glows in X-rays no matter what, we are getting a more complete picture of what was going on at the core of the explosion."
NuSTAR found that the titanium-44 was primarily found grouped around the center of Cas A. This has led NASA scientists to deduce a possible explanation for the death of these stellar giants.
It appears that the cause of a supernova is a massive shock wave that literally tears the star apart. Sometimes, however, the shock wave fails to reach a critical mass and stalls, preventing the star from shedding its outer layers and effectively preventing the supernova from taking place.
Information gathered from NuSTAR's observation of Cas A suggests that an exploding star sloshes around like a disturbed liquid, with the effect of kick-starting the stalled shock wave, continuing the supernova.
This chaotic new theory shakes off previous symmetrical theories regarding the processes required to create a supernova put forward by running data through powerful supercomputers, the results of which suggested an explosion which was symmetrical in all directions.
The ability to detect elements such as titanium-44 has also cast a level of doubt on some previous models of supernova explosions. One such model involved the dying star spinning at a great speed prior to exploding, however while searching the tell-tale jets ejected by the star during the high velocity spin, NuSTAR detected no signatures of titanium-44, meaning that the jets emitted from the star were not the trigger of the supernova explosion.
The team continues to examine Cas A in an attempt to further understand the dramatic ends of these stellar behemoths. A paper on the findings was recently published in Nature.
The video below shows a sloshing star going supernova.