Planet formation around intermediate mass stars

• Published in: Proceedings of the International Astronomical Union Vol. 3; no. S249; pp. 293 - 300
• Main Authors: Kretke, Katherine A., Lin, D. N. C., Turner, Neal J.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.10.2007
• Subjects: Angular momentum; Astronomy; Contributed Papers; Extrasolar planets; Gas giant planets; Ionization; Jupiter; Planet formation; Planetology; Protoplanetary disks; Stars; planetary systems: formation; protoplanetary disks
• ISSN: 1743-9213; 1743-9221
• DOI: 10.1017/S1743921308016724

We present a mechanism by which gas giants form efficiently around intermediate mass stars. MRI-driven turbulence effectively drives angular momentum transport in regions of the disk with sufficiently high ionization fraction. In the inner regions of the disk, where the midplane temperature is above ∼1000K, thermal ionization effectively couples the disk to the magnetic field, providing a relatively large viscosity. A pressure maximum will develop outside of this region as the gaseous disk approaches a steady-state surface density profile, trapping migrating solid material. This rocky material will coagulate into planetesimals which grow rapidly until they reach isolation mass. Around intermediate mass stars, viscous heating will push the critical radius for thermal ionization of the midplane out to around 1 AU. This will increase the isolation mass for solid cores. Planets formed here may migrate inwards due to type II migration, but they will induce the formation of subsequent giant planets at the outer edge of the gap they have opened. In this manner, gas giants can form around intermediate mass stars at a few AU.