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  Genesis spacecraft model  
  Don Burnett

Don Burnett,
Principal Investigator, Caltech

GENESIS - Discovery 5 Mission

Understanding the transition between star and planet

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!

  Doomed Star
Eta Carinae: Doomed Star.
HST, J. Morse, NASA.

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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Image of sun

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 >>> PDF icon

Sample analysis
Scientist analyzes sample

Genesis solar wind sample at
Johnson Space Center collection

Find out more about what's going on at
NASA's Johnson Space Center.

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Curator: Aimee Meyer
Updated: November 2009

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