LLNL

The sun and the solar system may have taken less than 200,000 years to form, according to scientists at the Lawrence Livermore National Laboratory after studying isotopes of the element molybdenum found on meteorites.

Scientists believe the material that makes up the sun and the rest of the solar system came from the collapse of a large cloud of gas and dust about 4.5 billion years ago. By observing other stellar systems similar to the Earth’s, astronomers have estimated that it can take between 1 million and 2 million years for a cloud of gas to collapse and a star to ignite. But this is the first study to provide numbers for the formation of the Earth’s solar system.

“Previously, the timeframe of formation was not really known for the solar system,” said LLNL cosmochemist Greg Brennecka, lead author of a paper appearing in Science. He said the study suggests the collapse that 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,” Brennecka said.

The oldest dated solids in the solar system are calcium aluminum inclusions, millimeter-sized objects found in primitive chondrite meteorites, that provide scientists a record of solar system formation. The inclusions formed in a high-temperature environment (more than 1,300 degrees Kelvin), probably near the young sun. Scientists believe they were then pushed out to the region where carbonaceous chondrite meteorites (and their parent bodies) formed, and where they are found today.

The majority of CAIs formed 4.567 billion years ago, over a period of about 40,000 to 200,000 years, according to scientific studies.

This is where the LLNL team comes in. The international team measured the molybdenum (Mo) isotopic and trace element compositions of a variety of CAIs from carbonaceous chondrite meteorites, including Allende, the largest carbonaceous chondrite ever found on Earth.

Because 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, the LLNL scientists believe they must have formed within the time span of cloud collapse.

Since the observed time span of stellar accretion is much longer than the CAIs took to form, the scientists were 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.

Former LLNL scientist Thomas Kruijer, now at the Museum für Naturkunde in Berlin, also contributed to this study, as well as researchers from the University of Münster, California Institute of Technology and the University of California, Santa Cruz. The work is funded by LLNL’s Laboratory Directed Research and Development program and NASA.