Title: Making other Earths: NBody Simulations of the Formation of Habitable Planets
1Making other Earths N-Body Simulations of the
Formation of Habitable Planets
- Sean Raymond
- University of Washington
Collaborators Tom Quinn (Washington) Jonathan
Lunine (Arizona)
2Habitable Zone temperature for liquid water
3Habitable Planets NEED WATER!
4The Paradox of Habitable Planet Formation
- Liquid water T gt 273 K
- To form, need icy material T lt 180 K
?icy
rocky?
snow line
5The Paradox of Habitable Planet Formation
- Liquid water T gt 273 K
- To form, need icy material T lt 180 K
?icy
rocky?
snow line
Local building blocks of habitable planets are
dry!
6So where did Earth get its water?
- Late Veneer Earth formed dry, accreted water
from bombardment of comets, or - ?Some of Earths building blocks came from past
snow line Earth did not form entirely from local
material
7To Guide the Habitable Planet Search (TPF,
Darwin), we Need to Know
- 1. Are habitable planets common?
- 2. Can we predict the nature of extrasolar
terrestrial planets from knowledge of - giant planet mass?
- giant planet orbital parameters (a, e, i)?
- c) surface density of solids?
8Overview of Terrestrial Planet Formation
- Condensation of grains from Solar Nebula
- Planetesimal Formation
- Oligarchic Growth Formation of Protoplanets (aka
Planetary Embryos) - Late-stage Accretion
9Oligarchic Growth growth by the few
- Protoplanets grow faster closer to the Sun!
- Take approx. 10 Myr to form at 2.5 AU
- Mass, distribution depend on surface density
Kokubo Ida 2002
10Simulation Parameters
- aJUP
- eJUP
- MJUP
- tJUP
- Surface density
- Position of snow line
11Snapshots in time from 1 simulation
Eccentricity
Semimajor Axis
12Radial Migration of Protoplanets
13Simulation Results
- Stochastic Process
- All systems form 1-4 planets inside 2 AU, from
0.23 to 3.85 Earth masses - Water content dry to 300 oceans (Earth has
3-10 oceans)
14Trends
- Higher eJUP ? drier terrestrial planets
- Higher MJUP ? fewer, more massive terrestrial
planets - Higher surface density ? fewer, more massive
terrestrial planets
15Effects of eJUP
16Habitability
- In most cases, planet forms in 0.8-1.5 AU
- In 1/4 of cases, between 0.9-1.1 AU
- Range from dry planets to water worlds with 50
times as much water as Earth
1711 planets between 0.9-1.1 AU
1843 planets between 0.8-1.5 AU
19Conclusions
- Most of Earths water was accreted during
formation from bodies past snow line - Terrestrial planets have a large range in mass
and water content - Habitable planets common in the galaxy
20Conclusions Contd
- Terrestrial planets are affected by giant
planets! Can predict the nature habitability
of extrasolar terrestrial planets - - Useful for TPF, Darwin
- Future develop a code to increase number of
particles by a factor of 10
21Additional Information
- 2003 Paper astro-ph/0308159
- Nature Science Updates Aug 21, 2003
(www.nature.com) - Email raymond_at_astro.washington.edu
- Talk to me!
22Additional Slides
23What is a habitable planet?
- Habitable Zone Temperature for liquid water on
surface - 0.8 to 1.5 AU for Sun, Earth-like atmosphere
- varies with type of star, atmosphere of planet
- Habitable Planet Need water!
24Initial Conditions
- Assume oligarchic growth to 31 resonance with
Jupiter - Surface density jumps at snow line
- Dry inside 2 AU, 5 water past 2.5 AU, 0.1 water
in between - Form super embryos if Jupiter is at 7 AU
25Simulation Parameters
- aJUP 4, 5.2, 7 AU
- eJUP 0, 0.1, 0.2
- MJUP 10 MEARTH, 1/3, 1, 3 x real value
- tJUP 0 or 10 Myr
- Surface density at 1 AU 8-10 g/cm2
- Surface density past the snow line
26Simulations
- Collisions preserve mass
- Integrate for 200 Myr with serial code called
Mercury (Chambers) - 6 day timestep
- currently limited to 200 bodies
- 1 simulation takes 2-6 weeks on a PC
27Data from our Solar System
Raymond, Quinn Lunine 2003
28(No Transcript)
29Distributions of Terrestrial Planets