© NASA, W. Sparks (STScI) and R. Sahai (JPL). Inset: SiC grain with ~8 micrometers in its longest dimension. Inset image courtesy of Janaína N. Ávila.Dust-rich outflows of evolved stars similar to the pictured Egg Nebula are plausible sources of the large presolar silicon carbide grains found in meteorites like Murchison.
Stars have life cycles. They're born when bits of dust and gas floating through space find each other and collapse in on each other and heat up. They burn for millions to billions of years, and then they die. When they die, they pitch the particles that formed in their winds out into space, and those bits of stardust eventually form new stars, along with new planets and moons and meteorites. And in
a meteorite that fell fifty years ago in Australia, scientists have now discovered stardust that formed 5 to 7 billion years ago-the oldest solid material ever found on Earth.
"This is one of the most exciting studies I've worked on," says Philipp Heck, a curator at the Field Museum, associate professor at the University of Chicago, and lead author of a paper describing the findings in
PNAS. "These are the oldest solid materials ever found, and they tell us about how
stars formed in our galaxy."
The materials Heck and his colleagues examined are called presolar grains-minerals formed before the Sun was born. "They're solid samples of stars, real stardust," says Heck. These bits of stardust became trapped in meteorites where they remained unchanged for billions of years, making them time capsules of the time before the solar system..
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