Eccentric Extrasolar Planets: The Jumping Jupiter Model HD217107b as imagined by Lynette Cook Stacy Teng TERPS Conference Dec. 9, 2004

Background Formation of Jupiter and Saturn in our Solar System –Gradual accumulation of planetesimals into cores followed by gravitational capture of gaseous envelopes from the surrounding nebula –Theory needs the giant planets to have formed beyond the “snow line” (at ~ 4AU) so volatiles could condense into ices for capture –Jupiter and Saturn formed on almost circular orbits as expected for protoplanets evolving from an accretion disk See the same thing in other planetary systems? –No!

Extrasolar Planets Jupiter-mass planets detected by Doppler shift –Biased toward massive planets with short orbital periods Most of the planets detected have semimajor axis < 4 AU What is the formation mechanism of these “Hot Jupiters”? Diagram by Marcy et al., updated March, 2004

Formation Theory “Hot Jupiters” formed near the stars [Bodenheimer et al. (2000)] –Need to accrete a lot of mass quickly Migration – tidal coupling [Lin et al. (1996)] –Interaction between the planet and the disk to move the planet inward Does not explain the large eccentricities that are observed

Formation Theory Migration – Jumping Jupiter Model –A system with 3 or more planets Encroachment of the Hill spheres as the planets grow –Numerical simulations Systems with 3 planets each with ~10 -3 M sun Planets had various initial separations Non-coplanar planets with initial inclinations 0.5, 1, and 1.5 degrees for the inner, middle, and outer planet Full tri-dimensional integrations using a mixed variable symplectic integrator with fixed stepsize of 20 days

Simulation Results Result of the simulations: –1 planet gets ejected from the system –1 planet moves to a smaller orbit –1 planet migrates further out –Theory works even for systems with planets formed within 2 AU

Comparison with Observations Statistical distribution of eccentricity agrees well with current data As the systems evolve, semimajor axis will get smaller as the orbits get circularized Future observations should detect distant planets in systems currently known to have planets

References Marzari, F. & Weidenschilling, S.J., 2002, Icarus, 156, 570 Levison, H.F. & Duncan, M.J., 1994, Icarus, 108, 18