Margaret Pan

SMACK: A NEW ALGORITHM FOR MODELING COLLISIONS AND DYNAMICS OF PLANETESIMALS IN DEBRIS DISKS

We present the Superparticle-Method/Algorithm for Collisions in Kuiper belts and debris disks (SMACK), a new method for simultaneously modeling, in three dimensions, the collisional and dynamical evolution of planetesimals in a debris disk with planets. SMACK can simulate azimuthal asymmetries and how these asymmetries evolve over time. We show that SMACK is stable to numerical viscosity and numerical heating over 107 yr and that it can reproduce analytic models of disk evolution. We use SMACK to model the evolution of a debris ring containing a planet on an eccentric orbit. Differential precession creates a spiral structure as the ring evolves, but collisions subsequently break up the spiral, leaving a narrower eccentric ring.

Detection of Exocometary CO within the 440 Myr Old Fomalhaut Belt: A Similar CO+CO2 Ice Abundance in Exocomets and Solar System Comets

Author(s): Matra, L; MacGregor, MA; Kalas, P; Wyatt, MC; Kennedy, GM; Wilner, DJ; Duchene, G; Hughes, AM; Pan, M; Shannon, A; Clampin, M; Fitzgerald, MP; Graham, JR; Holland, WS; Panic, O; Su, KYL | Abstract:

ON THE MASS AND ORIGIN OF CHARIKLO’S RINGS

Observations in 2013 and 2014 of the Centaur 10199 Chariklo and its ring system consistently indicated that the radial width of the inner, more massive ring varies with longitude. That strongly suggests that this ring has a finite eccentricity despite the fast differential precession that Chariklos large quadrupole moment should induce. If the inferred apse alignment is maintained by the rings self-gravity, as it is for the Uranian rings, we estimate a ring mass of a few times 10^16 g and a typical particle size of a few meters. These imply a short collisional spreading time of ~10^5 years, somewhat shorter than the typical Centaur dynamical lifetime of a few Myrs and much shorter than the age of the solar system. In light of this time constraint, we evaluate previously suggested ring formation pathways including collisional ejection and satellite disruption. We also investigate in detail a contrasting formation mechanism, the lofting of dust particles off Chariklos surface into orbit via outflows of sublimating CO and/or N_2 triggered after Chariklo was scattered inward by giant planets. This latter scenario predicts that rings should be common among 100-km class Centaurs but rare among Kuiper belt objects and smaller Centaurs. It also predicts that Centaurs should show seasonal variations in cometary activity with activity maxima occurring shortly after equinox.

A Complete ALMA Map of the Fomalhaut Debris Disk

National Science Foundation Graduate Research Fellowship [DGE1144152]; NRAO Student Observing Support; STFC; European Union through ERC [279973]; NASA [NNX15AC89G, NNX15AD95G/NEXSS, NNX15AK23G, NNX15AM35G]; NSF [AST-1518332, HST-GO-13726, AST-1412647]; NASAs Science Mission Directorate; Royal Society as a Royal Society University Research Fellow; Royal Society Dorothy Hodgkin Fellowship; Center for Exoplanets and Habitable Worlds; Pennsylvania State University; Eberly College of Science; Pennsylvania Space Grant Consortium

Stochastic flights of propellers

Kilometre-sized moonlets in Saturn’s A ring create S-shaped wakes called ‘propellers’ in surrounding material. The Cassini spacecraft has tracked the motions of propellers for several years and finds that they deviate from Keplerian orbits with constant semimajor axes. The inferred orbital migration is known to switch sign. We show using a statistical test that the time series of orbital longitudes of the propeller Bl´ eriot is consistent with that of a time-integrated