X-rays reveal uneven allotment of element made by blowup
JPL-Caltech, CXC/SAO and NASA
Giant stars are slightly off-kilter as they go kablooey, research in the Feb. 20 Nature suggests.
When massive stars run out of elements to fuse in their core, they collapse under their own gravity; the imploding material then bounces off the core and explodes in a bright display known as a core-collapse supernova. But computer simulations indicate that if material collapses symmetrically, as scientists long assumed, a star would not explode.
To address this conundrum, a team including Caltech astrophysicist Brian Grefenstette pointed NASA’s recently launched Nuclear Spectroscopic Telescope Array at Cassiopeia A, the remnant of a nearby core-collapse supernova whose light first reached Earth about 350 years ago. The researchers plotted the spatial distribution of high-energy X-rays emitted during the decay of the radioactive element titanium-44, which is forged in the depths of supernova explosions.
The X-rays revealed that the titanium is concentrated in several dense clumps, which suggests that the explosion was not symmetrical. The study offers an unprecedented look at a supernova’s inner workings, Grefenstette says, bringing scientists closer to learning exactly how these spectacular cosmic fireworks get set off.
B.W. Grefenstette et al. Asymmetries in core-collapse supernovae from maps of radioactive 44Ti in Cassiopeia A. Nature. Vol. 506, February 20, 2014, p. 339. doi: 10.1038/nature12997.
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