Wei Zhu（祝伟）
I'm now an Assistant Professor in the Department of Astronomy at Tsinghua University in Beijing.
An Inclusive View of Planetary Systems
Wei Zhu (祝伟)
TDLI Astrophysics Workshop
2018 December 20
HATNet
Keck
KMTNet
Kepler
Mayor & Queloz (1995)
Charbonneau et al. (2000)
Gillon et al. (2017)
Bond et al. (2003)
Hot Jupiters
Cold Jupiters
Cold Neptunes
Super Earths
Data from NASA Exoplanet Archive
(1%)
(10%)
(30%)
(?)
Image from Maruyama & Ebisuzaki (2017)
A Comprehensive Picture of
Planet Formation & Evolution
What is the initial condition (i.e., disk model)?
Do planets migrate in the gas disk?
Anything happens after disk disappears?
(See also R. Dong's talk)
Snow line
Minimum-mass solar/extra-solar nebula:
Weidenschilling (1977); Hayashi (1981)
\Sigma(r) \propto r^{-3/2}
Σ(r)∝r−3/2
The outer region dominates the mass and angular momentum budget
Nebula Model
Mimimum mass extra-solar nebula
Mimimum mass solar nebula
Chiang & Laughlin (2013)
(see also Schlichting 2014)
Planet Migration
Image credit: P. Armitage
- Transfers mass
- Changes orbital configuration: more mean-motion resonance
Image credit: M. Rex
Dynamical Instability
Credit: Raymond, Izidoro, & Morbidelli (2018)
- Transfers angular momentum (deficit)
- Modifies orbital spacing, eccentricity, inclinations
- Cold giants, if exists, play dominant roles
Super Earths alone
w/ outer Giants
HATNet
Keck
KMTNet
Understanding Planet Formation from Data
(by correlating different planets and planet populations)
Hot Jupiters
(~1%)
Cold Jupiters
(~10%)
Cold Neptunes
(?)
Super Earths
(30%)
Kepler Mission
- 1-m space telescope
- 10^5 target stars
- 4-yr observations
- ~5000 exoplanet detection (incl. 0 Earth-like)
Image credit: NASA/Ames, Batalha (2014)
Cui et al. (2012); Zhao et al. (2012); De Cat et al. (2015); Zong et al. (2018)
LAMOST-Kepler Survey
- 4mx6m; 5 deg^2 FoV
- 4000 fibers/plate
- ~40% of Kepler stars surveyed by 2017
If no dynamical instability...
- Planets very often reside in multi-planet systems
- Multi-planet systems are flat (<~5 deg); planets have (nearly) circular orbits
- Multi-planet systems should be well regulated (size & spacing)
- Planets very often reside in multi-planet systems
Architecture Revealed by
Kepler Mission
- Multi-planet systems are flat
- Multi-planet systems should be well regulated (size & spacing)
Image credit: NASA/Ames, Shallue & Vanderburg (2017)
Kepler Dichotomy?
Ballard & Johnson (2016)
(See also Lissauer et al. 2011, Johansen et al. 2012)
- If assuming small mutual inclinations, two populations are needed:
- compact systems
- 1-planet systems (or 2-planet with large mutual inclinations)
Transiting Planets (Tranets) vs. Planets
mutual inclination
No Sign for Kepler Dichotomy
Zhu et al. (2018)
(See also Xie et al. 2016, Weiss et al. 2018)
One-tranet hosts
Multi-tranet hosts
Transit Timing Variation (TTV)
- No interaction
- Interaction with additional planet
Holman & Murray (2005); Agol et al. (2005)
TTV Applications
Becker et al. (2015); Almenara et al. (2018)
- Characterizing known planets
- Detecting additional planets
Transit + TTV
-
Number of systems with k transiting planets
- ~50% in transit singles
-
# of systems with k transiting planets AND at least one showing TTV signals (Holczer++16)
- ~50% in transit singles
- Majority of transit singles are actually multi-planet systems with large mutual inclinations
Zhu, Petrovich, Wu et al., 2018
Transit singles
Transit multis
Intrinsic Architecture
{\rm inclination~dispersion~of~} \\
k{\rm -planet~system} \propto k^\alpha
inclination dispersion of k−planet system∝kα
Zhu, Petrovich, Wu et al., 2018
Planet-planet mutual inclinations affect the occurrence rate of planetary systems
{\rm \#~of~planetary~systems} = \frac{\rm \#~of~detected~systems}{\rm detectability~of~individual~system}
# of planetary systems=detectability of individual system# of detected systems
mutual inclination
Planet-planet mutual inclinations affect the occurrence rate of planetary systems
{\rm \#~of~planetary~systems} = \frac{\rm \#~of~detected~systems}{\rm detectability~of~individual~system}
# of planetary systems=detectability of individual system# of detected systems
Fraction of Sun-like stars with planets
- >50% (Fressin et al. 2013; Petigura et al. 2013; Winn & Fabrycky 2015)
- 30% (Zhu, Petrovich, Wu et al. 2018)
Kepler Planets Also Have Significant Eccentricities
\frac{P^2}{4\pi^2} = \frac{a^3}{GM_\star} = \frac{3(a/R_\star)^3}{4\pi G\rho_\star}
4π2P2=GM⋆a3=4πGρ⋆3(a/R⋆)3
\rightarrow T_0 \propto P^{1/3} \rho_\star^{-1/3}
→T0∝P1/3ρ⋆−1/3
T_0 = \frac{2R_\star}{2\pi a /P}
T0=2πa/P2R⋆
Seager & Mallen-Ornellas (2003)
Xie, Dong, et al. (2016)
(see also Van Eylen et al. 2018)
Intrinsic Architecture of
Inner Planetary System
- 30% of Sun-like stars have Kepler planets
- Fewer-planet systems are dynamically hotter
- Each system has on average 3 planets
- Our solar systems fits "well" in this picture
i,~e \propto k^\alpha
i, e∝kα
Zhu, Petrovich, Wu et al., 2018
Orbital eccentricity
- Planets very often reside in multi-planet systems: Yes
- Multi-planet systems are flat: No
- Multi-planet systems should be well organized (size & spacing): Maybe
Zhu, Petrovich, Wu et al., 2018
Intrinsic Architecture of
Inner Planetary System
Dynamical Instability Excites e, i
Kai Wu (吴开), et al. (in prep)
(see also Hansen & Murray 2013, Huang et al. 2017, etc)
Inner system alone cannot excite large enough mutual inclinations and eccentricities
Where Super Earths Form?
-
In situ
- Requires a massive disk
-
Migration
- Normal disk can work
- Mean-motion resonance pile-ups
Evidence for In Situ Formation?
- Period ratio distribution shows no preference for MMR pile-ups (Lissauer et al. 2011; Fabrycky et al. 2014)
- Asymmetry around period commesurability is a natural outcome of in situ formation (Petrovich et al. 2013)
Image from Winn & Fabrycky (2015)
Not conclusive: dynamical instability can modify the dynamical state
Where Super Earths Form?
-
In situ
- Requires a massive disk
- More inner super Earths, more outer cold Jupiters
-
Migration
- Normal disk can work
- More inner super Earths, fewer outer cold Jupiters
Super Earth-cold Jupiter relation
Cold Jupiters
Super Earths
Using data from NASA Exoplanet Archive
P({\rm CJ}|{\rm SE})
P(CJ∣SE)
(Plus another 22 systems from Kepler)
Zhu & Wu, 2018, AJ, 156, 92
(see also Bryan et al.2018)
Super Earth-cold Jupiter relation
Cold Jupiters
Super Earths
Using data from NASA Exoplanet Archive
P({\rm CJ}|{\rm SE}) \approx 33\% {\rm ~vs.~} P({\rm CJ})=10\%
P(CJ∣SE)≈33% vs. P(CJ)=10%
- Cold Jupiters are more likely found in super Earth systems.
Zhu & Wu, 2018, AJ, 156, 92
(see also Bryan et al.2018)
(Plus another 22 systems from Kepler)
Super Earth-cold Jupiter relation
Cold Jupiters
Super Earths
Using data from NASA Exoplanet Archive
Zhu & Wu, 2018, AJ, 156, 92
(see also Bryan et al.2018)
P({\rm CJ}|{\rm SE}) \approx 33\% {\rm ~vs.~} P({\rm CJ})=10\%
P(CJ∣SE)≈33% vs. P(CJ)=10%
- Cold Jupiters are more likely found in super Earth systems.
- Cold Jupiters are (almost) always accompanied by super Earths.
P({\rm SE}) = 30\%
P(SE)=30%
P({\rm SE}|{\rm CJ}) = \frac{P({\rm SE})}{P({\rm CJ})} P({\rm CJ}|{\rm SE}) \approx 100\%
P(SE∣CJ)=P(CJ)P(SE)P(CJ∣SE)≈100%
(Plus another 22 systems from Kepler)
Being confirmed by TESS!
10 M_{\rm J}\\
3~{\rm AU}\\
e=0.6
10MJ3 AUe=0.6
5 M_\oplus\\
6~{\rm d}
5M⊕6 d
Huang et al., (2018)
(see also Gandolfi et al. 2018)
- All-sky survey, bright stars
- 27 days per sector
- Looking for close-in planets around nearby stars
Transiting Exoplanet Survey Satellite
HATNet
Keck
KMTNet
Kepler
Hot Jupiters
(~1%)
Cold Jupiters
(~10%)
Cold Neptunes
Super Earths
(30%)
Data from NASA Exoplanet Archive
Hot Jupiters have distant companions
(Knutson et al. 2014, etc)
Hot Jupiters are lonely(?) (Steffen et al. 2010)
Super Earths & cold Jupiters tend to co-exist
(Zhu & Wu 2018)
An Inclusive View of Planetary Systems
(Un)Popularity of Solar system
P({\rm no~SE,~CJ}) = [1-P({\rm SE}|{\rm CJ})] \times P({\rm CJ}) \\
\approx 1\%
P(no SE, CJ)=[1−P(SE∣CJ)]×P(CJ)≈1%
Zhu & Wu, 2018, AJ, 156, 92
Hot Jupiters
(~1%)
Cold Jupiters
(~10%)
Cold Neptunes
Super Earths
(30%)
Hot Jupiters have distant companions
(Knutson et al. 2014, etc)
Hot Jupiters are lonely(?) (Steffen et al. 2010)
Super Earths & cold Jupiters tend to co-exist
(Zhu & Wu 2018)
- Solar system has no super Earth (~70%)
- Solar system has cold Jupiter (10%)
Inner-outer correlation
P({\rm SE}|{\rm CJ}) = 100\% \left( \frac{N_{\rm in,out}/N_{\rm out}}{5/12} \right) \left( \frac{R_\star/a_{\rm in}}{0.03} \right)^{-1}
\left( \frac{i_0}{4^\circ} \right)
P(SE∣CJ)=100%(5/12Nin,out/Nout)(0.03R⋆/ain)−1(4∘i0)
Herman, Zhu, & Wu (in prep)
i_0 \propto k^{-2}
i0∝k−2
1 yr
- 12 long-period giants in Kepler data
- 5 have inner transiting companions
- 1 has five inner planets:
Inner and outer regions correlate in occurrence rate & dynamical states
HATNet
Keck
Summary & Future Directions
Hot Jupiters
(~1%)
Cold Jupiters
(~10%)
Cold Neptunes
(?)
Super Earths
(30%)
- Planet formation is a global process
-
Systems with more planets are dynamically colder --> dynamical instability happened
- How was the gas envelop preserved/regained?
-
Inner and outer planetary systems show strong correlations --> in situ formation for super Earths
- What suppressed disk migration?
- What is the architecture of outer region down to lower masses (i.e., cold Neptune population)?
Inner
Outer
Hot Jupiters have distant companions
(Knutson et al. 2014, etc)
Hot Jupiters are lonely(?) (Steffen et al. 2010)
Super Earths & cold Jupiters tend to co-exist
(Zhu & Wu 2018)
Gaia, TESS, & RV Follow-ups
- TESS (2018-2020?) looks for close-in small planets; 1000s detections
- Gaia (2014-2024?) looks for distant giant planets; 1000s detections
- A ground-based RV instrument (2-4M USD) on a 2-4 m telescope has lots of science to do!
Space-based Microlensing
- WFIRST: NASA mission; 2.4 m; 1yr/5yr dedicated to microlensing; >2028
- Chinese Space Telescope (CST): ~2 m, detached to space station; early 2020s?
Penny et al. (2018)
(see also Zhu et al. 2014; 2017)
HATNet
Keck
Summary & Future Directions
Hot Jupiters
(~1%)
Cold Jupiters
(~10%)
Cold Neptunes
(?)
Super Earths
(30%)
- Planet formation is a global process
-
Systems with more planets are dynamically colder --> dynamical instability happened
- How was the gas envelop preserved/regained?
-
Inner and outer planetary systems show strong correlations --> in situ formation for super Earths
- What suppressed disk migration?
- What is the architecture of outer region down to lower masses (i.e., cold Neptune population)?
Inner
Outer
Wei Zhu (祝伟), CITA
Thanks for your attention!
Backup Slides
Things to improve on:
- Too much material to cover --> remove the microlensing part (could briefly mention it in the end, with 1 slide)
- Segmented topics --> unify everything into a single big question: how super Earths form?
- Theoretical motivation: in situ vs. migration
- Studying relations with CJ can help distinguish them
- This requires knowing P(SE)
- More theoretical stuff on the architecture(?):
- Why large mutual inclinations are hard to produce?
- Why 3 planets/system is an important result?
- Future explorations?
Talk Structure
- 1-slide overview of observations (techniques & results)
- Comprehensive overview of planet formation and evolution
- Kepler's puzzles
- How common are Kepler-like systems?
- Kepler dichotomy?
- How do super Earths form? (With focus on where they form)
- Summary
- Future directions
- TESS, Gaia follow-ups
- Space-based microlensing surveys
Kepler planets:
- Typical radii 1-4 R_Earth
- Close-in orbit
- Compact system
Kepler Telescope
Planets Migrate (or not?)
Credit: Cley & Nelson (2012)
Dynamical Instability?
Credit: M. Clement
Architecture of Planetary System
mutual inclination
- How many stars have (1, 2, ...) planets?
- What is the relative configuration of planetary orbits?
- Period distribution (=orbital spacing)
- Orbital inclinations
Hot Jupiter as (counter?) example
| Tidal migration | In situ formation | Disk migration | |
|---|---|---|---|
| Cold Jupiters | Yes | -- | -- |
| Super Earths | No | Yes | Yes |
Dawson & Johnson (2018)
Origin of Dynamical Hot State
Credit: C. Petrovich, with data from Hansen & Murray (2013)
Xie, Dong, et al. (2016)
- Transiting planets (tranets) vs. planets
- # of planets vs. # of planetary systems
Gravitational microlensing
Mao & Paczynski (1991), Gould & Loeb (1992), Gaudi (2012)
- Timescale: ~month
- Planet-to-star mass ratio
- Projected separation
Microlensing probes planets
beyond snow line
Gaudi (2012, ARAA)
WFIRST
Two-planet event OGLE-2012-BLG-0026
planet 2
planet 1
Han et al. (2013)
Both planets inside Einstein ring
Both planets outside Einstein ring
HATNet
Keck
KMTNet
Kepler
Hot Jupiters
(~1%)
Cold Jupiters
(~10%)
Cold Neptunes
Super Earths
(30%)
Data from NASA Exoplanet Archive
Friends of hot Jupiters (Knutson et al. 2014, etc)
Hot Jupiters are lonely(?) (Steffen et al. 2010)
Super Earth-cold Jupiter relations
(Zhu & Wu 2018, Bryan et al. 2018)
An Inclusive View of Planetary Systems
1. Two planets near resonance
2. P(CN|CJ)~100%
Work done by Sabrina Madsen (UBC)
50~M_\oplus~{\rm planet~not~predicted}\\
{\rm by~core~accretion~theory}
50 M⊕ planet not predictedby core accretion theory
Pollack et al. (1996)
Madsen & Zhu (in prep)
Face-on Edge-on
Effect of orbital orientations
Introducing eccentricity
Madsen & Zhu (in prep)
Introducing eccentricity
Madsen & Zhu (in prep)
Pluto & Neptune
Io, Europa, & Ganymede
Mean-motion resonance
Compare with known RV pairs
Madsen & Zhu (in prep)
Systems with cold Jupiters probably commonly have cold Neptunes
- A single detection out of ~20 microlensing systems with Sun-like hosts
- Low detection efficiency for Neptunes (~5%, Zhu et al. 2014).
- Perhaps all cold Jupiter systems also have cold Neptunes: P(CN|CJ)~100%.
- Mean-motion resonances may also be common.
Fraction of stars w/ planets is fundamental
- Tracing the planet formation efficiency as a function of stellar properties (mass, metallicity, etc)
Fischer & Valenti (2005)
f \propto Z^2 \propto N_{\rm Fe}^2
f∝Z2∝NFe2
Individual misaligned system: Kepler-108
Mills & Fabrycky (2017)
24 deg
Evidence from dynamical instability
Zhu & Wu, 2018, AJ, 156, 92
(including data from California-Kepler Survey, Petigura et al. 2017)
- (Undetectable) Cold Jupiters appear in high-metallicity, perturbing the inner system.
Small planet-metallicity correlation
Zhu, arXiv:1808.09451
(Un)Popularity of Solar system
- Conservative definition of Solar system-like?
- Dynamical evolution in early days?
Batygin & Laughlin (2015)
Evidence from dynamical instability
Zhu & Wu, 2018, AJ, 156, 92
- (Undetectable) Cold Jupiters appear in high-metallicity, perturbing the inner system.
w/ <=3 planets
w/ >=4 planets
Orbital solution of microlensing system
OGLE-2006-BLG-109: A Jupiter/Saturn analog
Gaudi et al. (2008); Bennett et al. (2010)
Orbital solution of microlensing system
Ryu (incl. Zhu) et al. (2018)
OGLE-2016-BLG-1190
OB0026: Sun-like host with a cold Jupiter & a cold Neptune
Beaulieu, Bennett, et al. (2016)
Compare with HR 8799
- Likely double 2:1 mean-motion resonances (b & c, c & d)
Fabrycky & Murray-Clay (2010)
(see also Wang et al. 2018)
b
c
d
An Inclusive View of Planetary Systems Wei Zhu (祝伟) TDLI Astrophysics Workshop 2018 December 20
Demographics (TDLI)
By Wei Zhu（祝伟）
Demographics (TDLI)
presentation on exoplanet demographics at TDLI on Dec 20, 2018
- 1,038
