Space and Planet Formation: Gassy Giants Had Small Beginnings

Scientists have often wondered how Jupiter and Saturn formed in 1 to 10 million years, whereas smaller Earth took 30 million or more years to reach today's form. Until now, it's all been based on the idea that planets are created when ice and rock form and gas and dust add their layers above them. But how could a rocky core like the ones the gassy giants have--nearly 10 times the size of Earth--form within the expected time period?

Researchers from the Southwest Research Institute (SwRI) and Queens University in Canada say they have solved this mystery. In their research, they found that "planetary pebbles," or icy objects about a foot in diameter, gathered and were helped by gas to stick together more efficiently. As these icy objects whirled into the orbit of a proto-planet, they joined with other rocks, helped to assimilate more efficiently by a gaseous headwind. The scientists recently published their work in Nature.

The researchers also say that after years of running computer simulations of the established planetary-formation method without success in the proper time frame, the current theory does the job, according to a release. 

"As far as I know, this is the first model to reproduce the structure of the outer solar system, with two gas giants, two ice giants (Uranus and Neptune), and a pristine Kuiper belt," said Dr. Hal Levison with SwRI Planetary Science Directorate and lead author of the paper, in the release. 

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