| Abstract |
Nearly 500 extrasolar planets have been discovered to date. The observed planetary
systems are very different from our solar system and surprisingly diverse. The
large number of planets detected suggests that planet formation is common around
main sequence stars. The major problem facing the scientific community with
regards to these discoveries is that observations cannot trace the history of
planet formation. Instead observations provide snapshots of either the early
stages of a protoplanetary gas disk orbiting a young star or the late stages after
planetary systems have formed. But the evolution from a young star to a planetary
system has not been observed. Thus, the challenge is to connect the early and late
stages of planet formation.
Planets form from the collisional growth of planetary building blocks,
planetesimals. In recent numerical work we have found that the resistance of
planetesimals to collisional erosion changes dramatically during planet formation.
Young planetesimals are weak aggregates that are easily disrupted due to efficient
momentum coupling during low-velocity collisions in the early phases of their
collisional evolution. However, as impact speeds increase the same weak
planetesimals become dramatically stronger because the shock from a supersonic
impact loses energy to deformation and phase changes. Our work identifies a
paradox for the early stages of planet formation. Objects in the km-size range
are weak and susceptible to collisional disruption. However, this disruption may
actually produce large amounts of debris that can be accreted by remaining
undisrupted planetesimals allowing growth. As we work to disentangle these sorts
of conundrums we can expect to put forward hypotheses for collisional remnants in
our solar system – for example, the dwarf planet Haumea and its collisional
family.
In this talk I will review the current understanding of planetesimal evolution and
discuss how future numerical simulations may connect observational snapshots to
provide a complete history of planet formation.
|