While exploding, supernovas not spherical

X-rays reveal uneven allotment of element made by blowup

LOPSIDED  Blue regions represent radioactive titanium in the supernova remnant Cassiopeia A, located about 11,000 light-years away. Previous surveys detected other elements, shown in red, yellow and green. The clumpy distribution of titanium suggests that the deceased star was not perfectly spherical when it exploded.

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.

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