March 6, 2013
Giants Like Jupiter May Have Formed In The Gas Disk Of Young Stars
Lawrence LeBlond for redOrbit.com - Your Universe Online
New research from Carnegie Institution for Science looks at how gas giants similar to Jupiter and Saturn formed and evolved. Using theoretical modeling, lead researcher Alan Boss provides clues that gas giants may form in the presence of gas disks that surround stars in their infancy. The work was recently published in the Astrophysical Journal.
By observing young stars that are surrounded by gas disks, Boss demonstrated that these celestial beings undergo periodic outbursts, some which last around a hundred years, and transfer mass from the disk onto the young, growing star, which in turn increases its luminosity. It is theorized that marginal gravitational instability within the gas disk drives the short bursts of mass accretion in these stars.
When it comes to how gas giants form around proto-suns, there a few theories.
One proposes that slowly growing ice and rock cores were followed by rapid accretion of gas from the surrounding gas disk, which led to the formation of super gas giants.
A second theory proposes that clumps of dense gas form spiral arms, which increase in mass and density and then form into a gas giant in a single step.
Regardless of how gas giants formed, Boss´ three-dimensional models demonstrate that they should have been able to survive the periodic outbursts of mass transfer from the gas disk to the proto-sun. One model similar to our own Solar System was stable for more than a millennium, while another model containing planets similar to Jupiter and Saturn remained stable for more than 3,800 years.
These models demonstrated that gas giants are able to avoid a forceful migration inward, avoiding being swallowed up by the growing star. The models also suggest these planets are capable of withstanding pressure of being tossed completely out of the planetary system by close encounters with one another.
"Gas giant planets, once formed, can be hard to destroy," said Boss, "even during the energetic outbursts that young stars experience."
Boss added that it is a reassuring outcome when the hunt for extrasolar gas giants shows that they are present in about 20 percent of the sun-like stars discovered. This indicates that improved theoretical understanding of the formation and evolution of gas giants is on the right path.