The extrasolar planets discovered to date possess unexpected orbital elements .
Most orbit their host stars with larger eccentricities and smaller semi-major axes than similarly sized planets in our own solar system do .
It is generally agreed that the interaction between giant planets and circumstellar disks ( Type II migration ) drives these planets inward to small radii , but the effect of these same disks on orbital eccentricity , \epsilon , is controversial .
Several recent analytic calculations suggest that disk-planet interactions can excite eccentricity , while numerical studies generally produce eccentricity damping .
This paper addresses this controversy using a quasi-analytic approach , drawing on several preceding analytic studies .
This work refines the current treatment of eccentricity evolution by removing several approximations from the calculation of disk torques .
We encounter neither uniform damping nor uniform excitation of orbital eccentricity , but rather a function d \epsilon / dt that varies in both sign and magnitude depending on eccentricity and other solar system properties .
Most significantly , we find that for every combination of disk and planet properties investigated herein , corotation torques produce negative values of d \epsilon / dt for some range in \epsilon within the interval [ 0.1 , 0.5 ] .
If corotation torques are saturated , this region of eccentricity damping disappears , and excitation occurs on a short timescale of less than 0.08 Myr .
Thus , our study does not produce eccentricity excitation on a timescale of a few Myr – we obtain either eccentricity excitation on a short time scale , or eccentricity damping on a longer time scale .
Finally , we discuss the implications of this result for producing the observed range in extrasolar planet eccentricity .