Isotope analysis of meteorites suggests that about 4.5 billion years ago, our solar system may have formed in less than 200,000 years.
Scientists estimate our universe to be about 13.8 billion years old. And our own solar system is a mere 4.5 billion years old. Humans, on the other hand, have only been on Earth a minute fraction of that broad piece of millennia. We emerged between five and seven million years ago.
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After looking at isotopes of the element molybdenum found on meteorites, a group of Lawrence Livermore National Laboratory (LLNL) concluded that it took the solar system less than 200,000 years to form.
Our Solar system formed from the collapse of a large gas cloud about 4.5 billion years ago.
Scientists first thought that the formation was a very gradual process, taking place across hundreds of millions of years. Subsequent studies had the solar system forming over two million years, as the Sun and the planets coalesced out of a great disk of gas and cosmic dust.
Now, the LLNL study suggests our solar system formed over a period of about 40,000 to 200,000 years.
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Scientists reached these conclusions by investigating lingering isotopes for the element molybdenum in calcium-aluminum-rich inclusions (CAIs) discovered in carbonaceous chondrite meteorites. CAIs range from a micrometer to a centimeter in size.
Previous measurements were based on observations of the formation of other systems elsewhere in the galaxy. CAIs, however, present a more promising approach because they are the oldest solid compounds found in the solar system.
These tiny inclusions in meteorites formed in a high-temperature environment (more than 1,300 Kelvin), probably near the young sun. They later migrated outward and became embedded into what became carbonaceous chondrite meteorites.
The majority of CAIs formed 4.567 billion years ago, over a period of about 40,000 to 200,000 years.
LLNL’s international crew measured the molybdenum (Mo) isotopic and trace element compositions of a selection of CAIs obtained from carbonaceous chondrite meteorites. These specimens included Allende, the largest carbonaceous chondrite ever found on Earth. Because they found that the distinct Mo isotopic compositions of CAIs cover the entire range of material that formed in the protoplanetary disk instead of just a small slice, these inclusions must have formed within the time span of cloud collapse.
Since the observed time span of stellar accretion (1-2 million years) is much longer than CAIs took to form, the team was able to pinpoint which astronomical phase in the solar system’s formation was recorded by the formation of CAIs, and ultimately, how quickly the material that makes up the solar system accreted.
Scientists published their research in Science.