Word: hydrogen
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Dates: during 1980-1989
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These are the theoretical scenarios. And at first 1987A seemed to be following the rules: it jumped from near invisibility to respectable brightness literally overnight, and while its wave-front speed was high, its spectrum revealed the unmistakable hydrogen-bearing signature of a Type II. But when the International Ultraviolet Explorer satellite reported a rapid drop in ultraviolet light, scientists began to wonder. Says Robert Kirshner, of the Harvard-Smithsonian Center for Astrophysics: "The spectrum we're seeing in the ultraviolet resembles the spectrum of a Type I. That's a puzzle." Admits Texas' Wheeler: "There are some funny features...
...real trouble will begin as the sun nears the 10 billion-year mark, when the thermonuclear fires that have been burning since its birth have fused all the hydrogen fuel in the solar core into helium. As the fuel runs out, the nuclear fire will die down, and the now largely helium core -- which has been kept distended by the heat -- will begin to contract under its own gravitational pull...
...February, barely two months after Soviet authorities unexpectedly released him from internal exile, Andrei Sakharov created a worldwide sensation by turning up at an international forum in Moscow. Sakharov, 65, a nuclear physicist often described as the "father of the Soviet hydrogen bomb" and a courageous defender of human rights in his homeland, spent nearly seven years under virtual house arrest with his wife Elena Bonner in the closed city of Gorky. During the February forum, Sakharov delivered three speeches eloquently expressing his concerns about human rights, U.S.-Soviet relations and the nuclear arms race. He made a slightly edited...
...principle divide every nuclear charge into four relatively independent systems: electronic, ballistic, atomic and (for a hydrogen device) thermonuclear. The reliability of the first three systems can be confirmed by laboratory tests supplemented by experiments in which a low-yield fission or fusion reaction releases a small quantity of neutrons, which can be measured by a counter close to the charge to be tested. The fourth system -- thermonuclear -- does not require testing in the majority of cases, since its reliability may be established by analogy to previously tested charges based on the same physical and design principles. At the same...
...degrees, and elements like silicon, sulfur and platinum, synthesized by the star, began spewing out over a vast region of space, where they will form clouds of gas and dust that can coalesce into new stars and planets. Indeed, most of the elements abundant on earth today, except hydrogen, were cooked up in some star that became a supernova. Says Woosley: "The calcium in our bones, the iron in hemoglobin and the oxygen we all breathe came from explosions like this...