Test puts pedal to heavy metal.Cosmic atom factories crank out gold and other heavy elements faster than scientists had suspected. So say physicists who have made the first measurement ever of the half-life of the isotope nickel-78. Scientists consider stellar explosions, called supernovas, the blast furnaces in which about half of all heavy elements found in nature today were, and continue to be, forged. In a supernova, light nuclei pack on extra neutrons and then become heavier elements when some of the neutrons decay into protons. Every additional proton moves the evolving nucleus up one place in the Periodic Table of the Elements Periodic Table of the Elements (showing atomic number and atomic symbol; click on atomic symbol for more detailed information) Groups . However, many aspects of the process, called rapid neutron capture Neutron capture is a kind of nuclear reaction in which an atomic nucleus collides with one or more neutrons and they merge to form a heavier nucleus. Since neutrons have no electric charge, they can enter a nucleus more easily than charged particles which are repelled by , remain poorly understood. Every heavy nucleus formed in a supernova briefly becomes nickel-78 along the way, says Hendrik Schatz of Michigan State University Michigan State University, at East Lansing; land-grant and state supported; coeducational; chartered 1855. It opened in 1857 as Michigan Agricultural College, the first state agricultural college. in East Lansing. "If [nickel-78] decays quickly, you can build up heavy elements quickly," he says. Using a particle accelerator to bombard bom·bard tr.v. bom·bard·ed, bom·bard·ing, bom·bards 1. To attack with bombs, shells, or missiles. 2. To assail persistently, as with requests. See Synonyms at attack, barrage2. 3. a beryllium beryllium (bərĭl`ēəm) [from beryl ], metallic chemical element; symbol Be; at. no. 4; at. wt. 9.01218; m.p. about 1,278°C;; b.p. 2,970°C; (estimated); sp. gr. 1.85 at 20°C;; valence +2. target with 100 billion krypton krypton (krĭp`tŏn) [Gr.,=hidden], gaseous chemical element; symbol Kr; at. no. 36; at. wt. 83.80; m.p. −156.6°C;; b.p. −152.3°C;; density 3.73 grams per liter at STP; valence usually 0. ions per second for about a week, Schatz and his colleagues produced exactly 11 nickel-78 nuclei. Few as they were, those nuclei were enough to reveal that the isotope's half-life is only 110 milliseconds, about a fourth of what theorists had predicted, Schatz says. The implication, he notes, is that elements heavier than nickel in the periodic table form faster in supernovas than physicists have predicted. Scientists are now using the result to refine models of the cosmos' element-making processes, Schatz says. |
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