Alternative Planet Formation Scenarios
Robert L. Kurucz (CFA)
Monday 13th September 2010, 12:00pm
Pratt conference room, 60 Garden Street
FU Orionis events:
I have worked out processes that conserve angular momentum by
ejecting protostellar material at the equator to balance infall
at high latitudes during an FU Ori event. Excess infall blocks
convective downflow but not convective upflow. The convective
upflow produces meridional flow toward the equator. Stellar
material inside the dipole torus that connects the star to the
disk flows outward carrying angular momentum to make an oblate
supergiant-type envelope that is not strongly coupled to the star.
When the infall drops back to normal levels, the oblate envelope
is slowly evaporated by strong UV and X radiation from the protostar.
Some matter flows or blows into the inner wall of the disk.
Magnetically-driven planet formation:
If the dipole field pulls out of the disk during an FU Ori
event, the field wraps and tangles around the extended envelope.
Reconnections compress the trapped plasma into an unstable magnetic
torus orbiting the star (a tokamak). The torus reconnects into
self-gravitating magnetic spheroids (spheromaks) that become
planetary cores. The reconnection radiation and winds heat and
compress the disk causing agglomeration out to the snow line.
The cores grow by collecting material infalling toward the star.
They are in unstable orbits that can change radically or they
can be ejected from the system. A core in a highly eccentric
orbit that goes far into the disk can become very massive
because it sweeps up material over a wide range of radii.
Radiatively-driven planet formation:
If the dipole field pulls out of the disk when the protostar
is not in an Fu Ori phase, the field wraps and tangles but there
is no large reservoir of plasma to compress. The reconnections
fill 75% of the surface of the star with CMEs and flares.
The reconnection radiation and winds heat and compress the disk
causing agglomeration out to the snow line. The agglomerated
material rapidly forms planetesimals and inner planets.
Classical planet formation:
Outer disks form planets by slow uniformitarian processes.