![]() By the time these dry planetesimals grown into large planets, most of their primordial water is gone. The decay of aluminum-26 might also have helped water and other volatiles escape from small planetesimals, drying these worlds. Its radioactive decay melts the rock at the world’s center, enabling heavier, metallic elements to sink into the core, while lighter elements float, remaining in the outer layers. “It might just be a property of all or many stellar systems.” An Important Ingredient for Rocky Planetsīeyond its value as a signature of extreme conditions, the decay of aluminum-26 (more so than other radioactive isotopes) seems to have played an important role in the formation of planetary bodies with layered interiors - such as Earth, with its core, mantle, and crust. “The fact that our solar system has aluminum-26 might not be unique or special,” Gaches says. This corresponds to about 4.5 billion years ago, when the CAIs found in meteorites formed. Gaches and his team found that aluminum-26 production peaks when the protostar blows out the surrounding gas, slowing down its accretion. ![]() ![]() The findings appear in The Astrophysical Journal. Now, Brandt Gaches (University of Cologne, Germany) and colleagues have developed new computer simulations showing that the young Sun would have not only made cosmic rays, it would have made them in the abundance required to produce meteorites’ aluminum-26. But researchers didn’t think forming stars could make cosmic rays. A carbonaceous chondrite meteorite, whose white specks are calcium–aluminium-rich inclusions.Īmerican Museum of Natural History / CC BY-SA 3.0Īnother way to make aluminum-26 is when cosmic rays, highly energetic charged particles, bombard other elements that might be present in a protostellar disk. The Sun itself might have produced the right conditions to produce the right amount of aluminum-26 within its own protostellar disk, the dust and gas that surrounds a newborn star. Researchers suggested that the isotope might have blown into the solar system from a nearby supernova or via the winds from extremely massive stars - or maybe both - making the birthplace of our Sun a rather busy neighborhood.īut new research points to a much simpler explanation that doesn’t require an outside source. Aluminum-26 decays pretty quickly, with a half-life of 717,000 years, which means that the isotope must have been abundant very early in the history of the solar system. In 1976, scientists found that when they first formed, these CAIs contained unusually high amounts of aluminum-26, a radioactive isotope that only forms in hot environments such as supernova explosions. CAIs were one of the first solids to condense in the protostellar disk around the still-forming Sun. One of those clues is calcium-aluminum-rich inclusions (CAIs), tiny bits of bright-colored material found in larger meteorites. What did the environment that formed the solar system look like? While most information about that long-ago era is lost, some meteorites and other primordial objects contain clues about that early epoch. An artist's illustration of the solar system in its early years.
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