The Terrestrial-Mass Free-Floating Planet Population

A talk I gave at the American Astronomical Society Division of Planetary Sciences Meeting 48 in Pasadena, CA

Transcript

1. Tom Barclay NASA Ames Research Center DPS 48 Oct 19 2016 The Terrestrial-Mass Free-Floating Planet Population
2. Collapse of molecular cloud core proto-star + disk (Shu, Adams, & Lizano 1987) Planets Form From Disks
3. Early stage dust grains planetesimals ~ μm ~1-10 km Middle stage planetesimals planetary embryos ~103 km Late stage embryos planets Classical Solar Nebular Theory
4. Hundreds of Simulations Sun + Jupiter + Saturn (at present orbits) Bimodal protoplanetary disk: 26 embryos (0.1 MEarth ) 260 planetesimals (0.01 MEarth ) Smallest fragments = 0.5 lunar mass Small change in initial conditions in each simulation 2 Gyr simulations, where all bodies fully interact gravitationally and collisionally
5. 5 WFIRST’s microlensing program is going to be searching for free-floating planets. How many will it find?
6. 6 WFIRST is going to be searching for free-floating planets. How many will it find?
7. 7 Properties of Ejected Material
8. 8 With giant planets ejections happen early Two epochs of ejection: first primordial material followed by processed material Giant planets only Times of Ejections
9. 9 Outer disk is ejected first Efficient radial mixing with no giant planets Fragments from inner system ejected later Dependence on Initial Semimajor Axis
10. 10 WFIRST will find plenty of Mars’ but few earths If Giant planets are rare, WFIRST finds no FFP WFIRST Detections
11. 11 Sun-Only
12. 12 Micro-Oort Clouds?
13. Conclusions We modeled ejections from planetary systems with and without giant planets With giant planet • Around 1.0 Mearth of material is ejected but in bodies no larger than 0.3 Mearth • i.e. lots go Mars’, no Earth’s • Ejections happen in two stages, an early stage of primordial material followed by a stage of process material With no giant planet about almost very little mass is ejected WFIRST will likely find a few dozen Mars’, but only if giant planets are not uncommon