Wei Zhu
I'm now an Assistant Professor in the Department of Astronomy at Tsinghua University in Beijing.
Wei Zhu (祝伟)
Planet Group Meeting
Tsinghua University
2021 March 5th
Zhu & Dong 2021, ARAA in press (arXiv:2103.02127)
Image credit: iLectureOnline
Transit (ground)
Transit (space)
RV
Microlensing
Imaging
Based on data from NASA Exoplanet Archive.
Hot Jupiters
Cold Jupiters
Super Earths
Cold Neptunes
Sub-Earths
What You See Is Not What You Get!
w/ known companions
w/o known companions
Based on data from NASA Exoplanet Archive.
Hot Jupiters
Cold Jupiters
Super Earths
Cold Neptunes
Sub-Earths
Spacing in mutual Hill radii
Transit duration \(T\)
Transit singles
Transit doubles
Transit triples
Transit quadruples
Based on DR25 MCMC parameters and Berger et al. (2020) stellar parameters.
Transit singles have \(\sigma_e\approx0.3\), whereas transit multis have \(\sigma_e\approx0.05\) (Van Eylen et al. 2015, 2019, Xie et al. 2016, Mills et al. 2019).
Transit duration \(T\)
Based on DR25 MCMC parameters and Berger et al. (2020) stellar parameters.
Systems with more planets have smaller eccentricities and are dynamically colder.
Transit singles
Transit doubles
Transit triples
Transit quadruples
\( \xi \equiv \frac{\rm (Transit~chord~length)_{in}}{\rm (Transit~chord~length)_{\rm out}} = \frac{T_{\rm in} P_{\rm in}^{-1/3}}{T_{\rm out} P_{\rm out}^{-1/3}} = \sqrt{\frac{1-b_{\rm in}^2}{1-b_{\rm out}^2}} \)
Transit chord length = \( 2\sqrt{1-b^2} = v \cdot T \)
\(b\)
\( \xi \equiv \frac{\rm (Transit~chord~length)_{in}}{\rm (Transit~chord~length)_{\rm out}} = \frac{T_{\rm in} P_{\rm in}^{-1/3}}{T_{\rm out} P_{\rm out}^{-1/3}} = \sqrt{\frac{1-b_{\rm in}^2}{1-b_{\rm out}^2}} \)
Weighted transit duration ratio \(\xi\)
Observed \(\xi\) distribution
\(\sigma_i=0\)
\(\sigma_i=1.8^\circ\)
\(\sigma_i=6^\circ\)
Figure from Ballard & Johnson (2016)
Transit doubles
Transit triples
Transit quadruples
\( \xi = \frac{T_{\rm in} P_{\rm in}^{-1/3}}{T_{\rm out} P_{\rm out}^{-1/3}} = \sqrt{\frac{1-b_{\rm in}^2}{1-b_{\rm out}^2}} \)
Zhu et al., 2018
(see also He et al. 2020)
\( \sigma_i,~\sigma_e \propto k^\zeta \)
Coplanarity \(\longrightarrow\)>50% of Sun-like stars have Kepler-like planets (e.g., Fressin et al. 2013, Petigura et al. 2013).
mutual inclination
(Colors mean different multiplicities.)
Cold Jupiters
Super Earths
22 from Kepler (triangles) + 39 from RV (squares)
\(M_{\rm b}=3.9\pm2.1\,M_\oplus\)
\(P_{\rm b}=4.78\) d
\(M_{\rm c}=14.6\pm2.3\,M_\oplus\)
\(P_{\rm c}=9.67\) d
\(M_{\rm d}=7.9\pm4.6\,M_\oplus\)
\(P_{\rm d}=42.90\) d
\(M_{\rm e}=2.1\pm0.1\,M_{\rm J}\)
\(P_{\rm d}=982\) d
Cold Jupiters
Super Earths
22 from Kepler (triangles) + 39 from RV (squares)
\( P({\rm SE}|{\rm CJ}) \cdot P({\rm CJ}) = P({\rm CJ}|{\rm SE}) \cdot P({\rm SE}) \)
\( \rightarrow P({\rm SE}|{\rm CJ})=100\% \)
Cold Jupiters
Super Earths
22 from Kepler (triangles) + 39 from RV (squares)
Zhu & Wu (2018), Bryan et al. (2019)
2 yr
Figure from Herman, Zhu & Wu (2019)
Pebbles (\(\sim\) cm)
Pebble isolation mass (\(\sim10\,M_\oplus\))
See reviews by Ormel (2017), Liu & Ji (2020)
Figure adapted from Penny et al. (2019)
(See also Lissauer et al. 2011, Ciardi et al. 2013, Millholland et al. 2017)
Radius of the inner planet \(R_\oplus\)
Radius of the outer planet \(R_\oplus\)
Image from Chatterjee & Tan (2014)
(See also Ormel et al. 2017)
Pebble isolation mass (Lambrechits et al. 2014, Liu et al. 2019)
$$M_{\rm iso} \approx 10 \left(\frac{h/r}{0.04}\right)^3 \left(\frac{M_\star}{M_\odot}\right) M_\oplus $$
Pebble
(\(\sim\) cm)
Detection threshold
Systems around
Radius of inner Kepler planet
Radius of outer Kepler planet
Planet size
Stellar noise
Numbers
Planet size
(see also Murchikova & Tremaine 2020)
Systems around
Radius of inner Kepler planet
Radius of outer Kepler planet
Planet size
Stellar noise
Numbers
Planet size
(see also Murchikova & Tremaine 2020)
Future super-Kepler mission (e.g., Earth 2.0) should find sub-Earths in known systems.
(see also Murchikova & Tremaine 2020)
See Zhu (2020) and Murchikova & Tremaine (2020).
Figure adapted from Penny et al. (2019)
Figure adapted from Penny et al. (2019)
Figure from Zhu & Wu (2018)
(Kepler planets around Sun-like stars, based on Kepler DR25 & Gaia parameters)
0.4 \(R_\oplus\)
0.9 \(R_\oplus\)
1.0 \(R_\oplus\)
0.5 \(R_\oplus\)
11 \(R_\oplus\)
9 \(R_\oplus\)
4.0 \(R_\oplus\)
3.9 \(R_\oplus\)
See Zhu (2020) and Murchikova & Tremaine (2020).
By Wei Zhu