Word: outward
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...last week scientists had already amassed more data than they could immediately analyze, confirming some theoretical predictions and making several observations that for the time being puzzled everyone. Earliest readings showed that the shell of gases expanding around 1987A was initially traveling outward at nearly 10,000 miles per second. Since then the color of the supernova has been changing from blue to red much faster than expected. "That change is five to ten times faster than other supernovas," says Robert Williams, director of the U.S.-financed Cerro Tololo Inter-Observatory in Chile. This phenomenon indicates that the rapid expansion...
...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...
...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...
...surrounding the core. The interior of the sun will now be hotter than ever, a dense core of incandescent helium surrounded by a thin shell of hot, fusing hydrogen. Over the next few hundred million years, heat from the core will drive surface layers of the sun so far outward that they will cool to about two-thirds of the current 6,000 degrees C surface temperature, and redden. The sun will have become a red giant, so large that it will engulf the planet Mercury, perhaps extending to encompass the orbit of the earth. Even if the swollen...