- 3428 - STARDUST - older than the Earth? Scientists have discovered the oldest solid material on Earth: 7-billion-year-old stardust trapped inside a meteorite. This stardust provides evidence for a 'baby boom' of new stars that formed 7 billion years ago, contrary to thinking that star formation happens at a steady, constant rate.
------------- 3428 - STARDUST - older than the Earth.
- It is great to study stuff that is older than your are. But, it keeps getting harder to find. I had to look to the stars. 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.
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- 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.
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- These are the oldest solid materials ever found, and they tell us about how stars formed in our galaxy. The materials are called “presolar grains-minerals” formed before the Sun was born. They're solid samples of stars, real stardust. 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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- Presolar grains are rare, found only in about five percent of meteorites that have fallen to Earth, and they're tiny-a hundred of the biggest ones would fit on the period at the end of this sentence.
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- The largest portion of this “Murchison meteorite” has a treasure trove of presolar grains that fell in Australia in 1969. Once the presolar grains were isolated, the researchers figured out from what types of stars they came and how old they were.
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- Using exposure age data, which basically measures their exposure to cosmic rays, which are high-energy particles that fly through our galaxy and penetrate solid matter. Some of these cosmic rays interact with the matter and form new elements. And the longer they get exposed, the more those new elements form.
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- By measuring how many of these new cosmic-ray produced elements are present in a presolar grain, we can tell how long it was exposed to cosmic rays, which tells us how old it is.
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- The researchers learned that some of the presolar grains in their sample were the oldest ever discovered-based on how many cosmic rays they'd soaked up, most of the grains had to be 4.6 to 4.9 billion years old, and some grains were even older than 5.5 billion years.
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- Our Sun is 4.6 billion years old, and Earth is 4.5 billion.
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- But the age of the presolar grains wasn't the end of the discovery. Since presolar grains are formed when a star dies, they can tell us about the history of stars. And 7 billion years ago, there was apparently a bumper crop of new stars forming-a sort of astral baby boom.
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- This finding contributes to a debate between scientists about whether or not new stars form at a steady rate, or if there are highs and lows in the number of new stars over time. This is direct evidence of a period of enhanced star formation in our galaxy seven billion years ago with samples from meteorites.
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- By examining the way that the minerals in the grains interacted with cosmic rays, the researchers also learned that presolar grains often float through space stuck together in large clusters.
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- Doing astronomy with geological samples you can hold in your hand looking at the history of our galaxy. Stardust is the oldest material to reach Earth, and from it, we can learn about our parent stars, the origin of the carbon in our bodies, the origin of the oxygen we breathe. With stardust, we can trace that material back to the time before the Sun.
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- January 24, 2022 STARDUST - older than the Earth? 3428
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----------------------------- Wednesday, January 26, 2022 ---------------------------
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