The future of
planetary architectures
Melvyn B. Davies
Department of Astronomy and Theoretical Physics
Lund Observatory
www.astro.lu.se
We are fortunate
1. Our planetary system is stable
2. Our planet is within the habitable zone
3. Our planet is not too wet and not too dry
4. We are hit sometimes but not too often
5. We are in a safe region of the Milky Way
The Solar System is not like the others
Winn & Fabrycky 2015
Eccentric exoplanets
Winn & Fabrycky 2015
An unstable system
0.6
0.1
Scattering is seen to
reproduce the observed
eccentricity distribution.
0.08
0.4
e
e
0.06
0.04
0.2
0.02
0
1.75
0.05
0
“PLANET1.aei.0” using 1:2
“PLANET2.aei.0” using 1:2
“PLANET3.aei.0” using 1:2
1.5
0.04
0.03
|∆a| /AU
a/AU
1.25
1
0.02
0.75
0.01
0.5
0
2500
t/yr
5000
0
2000
e.g. Davies et al. 2014
2500
t/yr
3000
Do giant instabilities affect habitability?
1.0
4Gb
Cumulative distribution
0.8
3J
0.6
0
0.4
0.2
0.4
0.6
0.8
Probability of resilient habitability
1
0.2
0.0
0.0
0.2
0.4
0.6
0.8
Final eccentricity (G1 or inner J)
1.0
Carrera, Davies & Johansen 2016
Kepler finds many Super Earths
TESS
CHEOPS
Mustill, Davies & Johansen 2015
A better view of the Galaxy with Gaia
GAIA
1) Spiral arm pattern speed
2) Orbit of Sun
3) Origin of Hot Jupiters
NASA/JPL-Caltech/ESO/R. Hurt
Questions to be answered
1. Rock vs. ice vs. gas for close-in planets?
2. How common are stable systems?
3. What is the role of migration?
4. Are hot Jupiters formed by migration or by
scattering?
5. How common are Earth-like planets around
Sun-like stars? (The T.H.E.)