Word: core
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Dates: during 1980-1989
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...inside out, merged to a common inward-driving sphere; the spherical detonation wave crossed into the second shell of solid fast Composition B and accelerated; hit the wall of dense uranium tamper and became a shock wave and squeezed, liquefying, moving through; hit the nickel plating of the plutonium core and squeezed, the small sphere shrinking, collapsing into itself, becoming an eyeball...
...evolution in general and of how, for some stars, an inevitable violent death occurs. The basic theme: a star performs a continual balancing act between its own immense gravity, which tries to pull all of its matter in toward the center, and the intense thermonuclear energy radiating from its core, which pushes the matter outward, keeping the star in the form of a distended ball of hot gases. For most of a star's lifetime, these forces are in equilibrium...
When the nuclear fuel is exhausted and the fusion reactions stop, however, gravity takes over. Without the outward pressure needed to keep it "inflated," the core of the star begins to collapse like a deflating balloon, its matter crushing down toward the center. For a star about the size of the sun, the collapse stops after several intermediate steps when the stellar material is compressed so much that its atoms virtually touch, forming what physicists call degenerate matter; what prevents further collapse is the tendency of the atoms' negatively charged electrons to repel one another. The star has become...
...long. The instant the remaining silicon in the core is fused into iron, the thermonuclear reactions stop. Without enough radiation pressure to sustain it, the now all-iron core, hidden under the star's outer layers, begins its final, catastrophic collapse. In the incredibly short time of just 1 second, according to University of Arizona Astrophysicist Adam Burrows, the core is compressed to more than the density of an atomic nucleus. "It's as if the earth had suddenly collapsed to the size of New York City," says Burrows. "At this point the rest of the star is oblivious...
...resulting shock waves spread outward through the core, enter the star's still unsuspecting outer layers, and hours later reach the surface, spewing the star's laboriously made elements into space in a mammoth explosion. All that is left behind is the neutron core, the strange entity that astronomers call a neutron star...