New theoretical modeling by Carnegie's Alan Boss provides clues to how the gas giant planets in our solar system—Jupiter and Saturn—might have formed and evolved. New stars are surrounded by rotating gas disks during the early stages of their lives. Gas giant planets are thought to form in the presence of these disks.
Observations of young stars that still have these gas disks demonstrate that sun-like stars undergo periodic outbursts, lasting about 100 years, which transfer mass from the disk onto the young star, increasing its luminosity. It is thought that these short bursts of mass accretion are driven by marginal gravitational instability in the gas disk.
"Gas giant planets, once formed, can be hard to destroy," said Boss, "even during the energetic outbursts that young stars experience."
Boss developed highly detailed, three dimensional models demonstrating that regardless of how gas giant planets form, they should have been able to survive periodic outbursts of mass transfer from the gas disk onto the young star.
One model similar to our own Solar System was stable for more than 1,000 years, while another model containing planets similar to our Jupiter and Saturn was stable for more than 3,800 years. The models showed that these planets were able to avoid being forced to migrate inward to be swallowed by the growing proto-sun, or being tossed completely out of the planetary system by close encounters with each other.
Given that searches for extrasolar gas giant planets have found them to be present around about 20% of sun-like stars, this is a reassuring outcome. It suggests that our improved theoretical understanding of the formation and orbital evolution of gas giants is on the right track.
This research was supported in part by the NASA Origins of Solar Systems Program and contributed to in part to the NASA Astrobiology Institute. The calculations were performed on the Carnegie Alpha Cluster, the purchase of which was partially supported by a NSF Major Research Instrumentation grant.
The study was published recently by the Astrophysical Journal.
The Daily Galaxy via Carnegie Institution for Science
The image at the top of the page is an ALMA observation of the disc and gas streams around HD 142527. Credit: ALMA (ESO/NAOJ/NRAO), S. Casassus et al.