Scientists estimate solar nebula's lifetime February 9, 2017 Please Register or Log in to view the hidden image! Solar system. Credit: NASA About 4.6 billion years ago, an enormous cloud of hydrogen gas and dust collapsed under its own weight, eventually flattening into a disk called the solar nebula. Most of this interstellar material contracted at the disk's center to form the sun, and part of the solar nebula's remaining gas and dust condensed to form the planets and the rest of our solar system. Now scientists from MIT and their colleagues have estimated the lifetime of the solar nebula—a key stage during which much of the solar system evolution took shape. This new estimate suggests that the gas giants Jupiter and Saturn must have formed within the first 4 million years of the solar system's formation. Furthermore, they must have completed gas-driven migration of their orbital positions by this time. "So much happens right at the beginning of the solar system's history," says Benjamin Weiss, professor of earth, atmospheric, and planetary sciences at MIT. "Of course the planets evolve after that, but the large-scale structure of the solar system was essentially established in the first 4 million years." Read more at: https://phys.org/news/2017-02-scientists-solar-nebula-lifetime.html#jCp
http://science.sciencemag.org/content/355/6325/623 Meteorite magnetism in the early solar system The young solar system contained a disc of gas and dust within which planet formation occurred. The disc eventually dissipated after the Sun ignited and the planets formed, but exactly when that happened has been difficult to determine. Wang et al. measured tiny magnetic fields preserved in angrites, an ancient type of meteorite. They interpret a drop in magnetic field strength about 4 million years after the solar system formed as a sign that the gas had cleared—along with the magnetic field that it carried. The results will enhance our understanding of planet formation, both in our solar system and around other Sun-like stars. Science, this issue p. 623 Abstract A key stage in planet formation is the evolution of a gaseous and magnetized solar nebula. However, the lifetime of the nebular magnetic field and nebula are poorly constrained. We present paleomagnetic analyses of volcanic angrites demonstrating that they formed in a near-zero magnetic field (<0.6 microtesla) at 4563.5 ± 0.1 million years ago, ~3.8 million years after solar system formation. This indicates that the solar nebula field, and likely the nebular gas, had dispersed by this time. This sets the time scale for formation of the gas giants and planet migration. Furthermore, it supports formation of chondrules after 4563.5 million years ago by non-nebular processes like planetesimal collisions. The core dynamo on the angrite parent body did not initiate until about 4 to 11 million years after solar system formation.
Another interesting article on the time frame of planetary formation from the solar nebular, and a nice supplementary article to the previous WD and "stuff of life" one previous.
