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Divining a New Solar System Timeline from Rocks Older than Earth

We ogle images of gorgeous star-forming nebula from afar, but it’s tougher to reconstruct the nebula that formed our own cosmic hood.
NASA/JHUAPL/Hernan Canellas

Nebulas are among the most visually astounding phenomena in the universe. These expansive clouds of gas and dust act as stellar nurseries, gestating baby stars as they condense under their own gravitational momentum. Our own Sun was born within one of these collapsing clouds some 4.6 billion years ago, a process that rapidly transformed its environment into the flattened "solar nebula." This was the ancient birthplace of the planets and assorted space junk within the modern solar system.

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Sadly, there's no way to directly image this bygone nebula that laid down the foundations of our cosmic neighborhood. But nonetheless, researchers are finding ingenious ways to unravel the mysteries of this ancestral solar womb.

Case in point: A team led by Massachusetts Institute of Technology (MIT) planetary scientist Huapei Wang has now pinpointed the lifespan of the solar nebula with greater accuracy than ever before. Previous attempts to guage the solar nebula's age range had produced figures ranging from one to 10 million years after the Sun's nuclear furnace first ignited.

But by examining the properties of angrites, an ultra-rare class of meteorites older than Earth itself, Wang and his colleagues have narrowed down the nebula's lifetime to three to four million years, post-ignition. Their research was published Thursday in the journal Science.

Image result for solar nebula

"So much happens right at the beginning of the solar system's history," commented paper co-author Benjamin Weiss, professor of earth, atmospheric, and planetary sciences at MIT, in a statement. "Of course the planets evolve after that, but the large-scale structure of the solar system was essentially established in the first four million years."

The team used four angrite specimens, sourced from meteorite impacts in Argentina, Brazil, Antarctica, and the Sahara Desert. These basaltic visitors from outer space were formed about 4.653 billion years ago, while the solar nebula and its powerful magnetic field encapsulated the infant solar system. Forged in ultra-hot conditions, the igneous specimens were imprinted with the magnetic fingerprints of the solar nebula as they cooled.

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Wang's team was able to decipher this primordial record by studying the meteorites' remnant magnetization at the MIT Paleomagnetism Laboratory. The electron alignment within the samples revealed that the nebula's magnetic influence was waning when these rocks were created, suggesting it had faded into obscurity within four million years of the Sun's first light.

The team hopes sample-return trips to pristine asteroids, including the ongoing OSIRIS-REx and Hayabusa 2 missions, will further elucidate the timeline of the solar nebula, and thus the birth of the solar system itself.

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