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Don Burnett,
Principal Investigator, Caltech |
GENESIS - Discovery 5 Mission
Understanding the transition between star and planet
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Cosmologists believe that the universe was created about 15 billion years ago with the "big bang," a cosmic explosion which resulted in an expanding cloud of the two lightest elements -- the gases hydrogen (H) and helium (He). That's all there was; the Periodic Table back then had only two elements! In some places there were higher concentrations of gas than in others, and the mutual gravitational attractions of the gas molecules in those local concentrations led to the growth of the first generation of stars. As more and more material fell into a new star the pressure at its center finally became high enough to start the process of nuclear fusion in which the nuclei of hydrogen and helium merged to form heavier elements. This was accompanied by the release of energy which made the star begin to shine -- and then there was light!
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Eta Carinae: Doomed Star.
HST, J. Morse, NASA.
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Eventually all the hydrogen and helium, and those products which could be used to generate energy in the core of the star, were exhausted. Then, the nuclear furnace was extinguished and the outer layers of the star could no longer be supported against gravity. What happened next depended on the mass of the star. In some cases the star became a supernova, exploding violently, rapidly creating even heavier elements, and spewing much of the stellar material into space.
In other cases, the process was slower; instead of an explosion, nuclear reaction products from interior zones were mixed to the surface and then lost to space when the outer layers were blown off. The end results were similar, with the space between the stars being enriched with heavy elements, many of which condensed to form small solid grains. These processes happened over and over again, with each successive generation of stars starting off with higher abundances of heavy elements than the previous generation. Learn more >>> |
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Out of the yawning September sky, pieces of the
sun tumbled toward the Utah desert. They were
captured solar particles, holding clues to the birth
of the solar system, and being returned to Earth in
a shiny, 200-kilogram capsule. The plan was for
parachutes to slow the pocket watch-shaped craft,
allowing a helicopter to swoop in, snatch it from
midair, and gently lower the fragile contents to the
ground. But on this bright morning in 2004, the
parachutes didn't open, and the helicopter didn't
have a chance. The capsule spun and wobbled as it
plunged into the ground at more than 300 kilometers
per hour. "Snatching Some Sun," by David Woo; Engineering and Science, No. 4, 2007.
Full story >>> 
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