Isotopes suggest solar system formed in under 200,000 years
Based on isotope analysis of meteorites, a team of scientists at the Lawrence Livermore National Laboratory (LLNL) has determined that about 4.5 billion years ago, our solar system may have formed in less than 200,000 years.
At one time it was thought that the formation of the solar system was a very gradual process, taking place across hundreds of millions of years. More recent revisions 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.
The new LLNL study suggests that the transition from large cloud of gas to nascent solar system was just 40,000 and 200,000 years. This conclusion is based on an isotopic analysis of the element molybdenum in calcium-aluminum-rich inclusions (CAIs) found in carbonaceous chondrite meteorites, which are a direct record of the solar system's formation.
The previous time scale estimate of between one and two million years was a deduction based on observations of the formation of other systems elsewhere in the galaxy. CAIs present a more promising approach, because they are the oldest solid compounds found in the solar system.
Formed at temperatures of over 1,300º Kelvin (1,880º F, 1,027º C) near the new sun, these micrometer to centimeter sized particles later migrated outward and became embedded into what became carbonaceous chondrite meteorites.
By measuring the molybdenum isotopes in a number of carbonaceous chondrite meteorites found on Earth, the LLNL team found the isotopic composition in the CAIs, was uniform throughout the entire range of the primordial material, which means that the CAIs were spread throughout the protoplanetary disc. The conclusion is that since the CAIs formed during a period 4.567 billion years ago over a span of 40,000 to 200,000 years and had then spread uniformly, that's how long it took for the system to form as the dust and gas cloud collapsed.
"Previously, the timeframe of formation was not really known for our solar system," says LLNL cosmochemist Greg Brennecka. "This work shows that this collapse, which led to the formation of the solar system, happened very quickly, in less than 200,000 years. If we scale this all to a human lifespan, formation of the solar system would compare to pregnancy lasting about 12 hours instead of nine months. This was a rapid process."
The research was published in Science.