University of Copenhagen/Lars Buchhave

Artist's impression of a protoplanetary disk forming baby planets around our young sun.University of Copenhagen/Lars Buchhave

The stellar nursery that produced our solar system separated out from the rest of the galaxy some 30 million years before the sun was born, new research shows.

“Considering that it took less than 100 million years for the terrestrial planets to form, this incubation time seems astonishingly long,” chemist and planetary scientist Martin Bizzarro, with the University of Copenhagen Natural History Museum in Denmark, writes in an article in this week’s Science.

The study reconciles a long-standing discrepancy between the abundances of two radioactive isotopes -- iodine-129 and hafnium-182 -- at the time of the sun’s birth some 4.567 billion years ago. The samples came from meteorites and were previously analyzed in laboratories.

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“We did not measure these nuclei in meteorites, but explained the data already available,” lead researcher Maria Lugaro with Monash University in Australia, wrote in an email to Discovery News.

“The new research “delivers the first successful interpretation of meteoritic data that were presented beforehand but were difficult to explain,” she added.

Lugaro and colleagues calculated that the last time elements such as lead were added into the solar system’s birthing materials was no more than 30 million years before formation of the sun.

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“This timing is significant because it represents the maximum time that the solar system matter was isolated from the rest of the galaxy -- and hence could not experience any more addition -- inside a stellar nursery before the formation of the sun,” Lugaro said.

Not only was the sun’s birthplace old, it also was likely very crowded, a finding that has implications for understanding how other star systems evolve, including those that host potentially habitable planets.

“The planets in the solar system survived dynamical interaction with the sun's siblings. At the moment, we cannot exclude that the sun's nursery may have been a very massive, long-living region where thousands or even tens of thousands of stars were born together. In this case, we would have the proof that extrasolar planetary systems can form and survive in crowded conditions,” Lugaro said.

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Stars form in regions of space that are dense and cooler than interstellar areas, which are regularly bathed in hot matter, like lead, from dying stars.

Researchers hope to narrow down the time frame for the sun’s prenatal years by studying other radioactive nuclei heavier than iron, such as lead-205.

“We are planning to reanalyze the nuclear physics information required in our stellar simulation to try to work out a complete picture that accounts for as many of these nuclei as possible,” Lugaro said.