Beryllium-10
Beryllium-10 is a radioactive isotope made by cosmic rays, used to measure exposure and terrestrial ages of meteorites.
Beryllium-10 is a radioactive isotope with a half-life of about 1.39 million years. It is produced when high-energy cosmic rays smash into atoms of oxygen, magnesium, silicon and other elements in a meteoroid travelling through space.
While a meteoroid is exposed, beryllium-10 builds up until production and decay balance. When the meteorite lands on Earth, the atmosphere shields it, production stops and the beryllium-10 begins to decay. Comparing measured amounts with expected production rates, often together with other isotopes such as chlorine-36 and aluminium-26, gives the cosmic-ray exposure age and the terrestrial age.
In 2000, researchers reported excess boron-10 in CAIs from Allende, showing that beryllium-10 was alive when they formed. Because supernovae do not make it, this suggests it was produced by intense radiation from the young Sun acting on nearby material, offering a glimpse of the early Sun's violent activity.
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