Exoplanet Research with TMT
Jianghui JI
( Purple Mountain Observatory, Chinese Academy of Sciences )
2014/01/13, TMT-Planetary Science Definition Workshop, Beijing
Outline
Introduction
Overview of our work
Scientific issues with TMT
Summary
Detected exoplanets
As of 12 Jan., 1056 planets / 175 multiple planetary systems
Radial velocity or Astrometry: 539 planets orbiting 405 stars
Transit technique: 430 planets orbiting 327 stars
Akeson et al., 2013, PASP
Scientific Issues
• 空间与地面的大量观测与统计表明，在恒星附近有很多短周期气态
巨行星、类地行星。这些行星是在当地（in-situ）形成还是在行星
盘经历了轨道迁移，抑或是引力不稳定性导致？
•在迁移过程中原行星是否仍然吸积盘中气体而继续生长？什么动力
学机制使行星轨道迁移停止？
• 短周期行星长期潮汐和动力学演化状况如何？
•它们内部结构与物质分布如何，与太阳系行星有何异同？
•大气成分有何特征，是否存在水、二氧化碳、甲烷、氧气等适合生
命存在的重要化学指纹？
•是否可以发现宜居的地球大小的行星？
Current Research and Future Projects
Current Research:
Dynamics and evolution of planetary system,
Internal structure of terrestrial planets,
Planetary atmosphere and spectroscopy,
Follow-up Observations
Future Projects:
Atmosphere modelling and retrieval
Transit follow-up observations: TrES-3b
(In collaboration with NTHU, Taiwan) TrES-3 b transit event on Oct. 9, 2010,
observed by 105/120 cm telescopic finder with 4K×4K drift scanning CCD finder
at Xuyi Observation Station, Purple Mountain Observatory. Curve fitted and
physical parameters derived using tools supplied by TRESCA database.
Jiang et al., 2013, AJ
Catalogue data
Measured data
Rp:
1.295 +/- 0.081 RJup
1.183 -0.039+0.038 RJup
R*:
0.813 +/- 0.027 RSun
fixed, errors included in i
A:
0.0226 +/- 0.0013 AU
fixed, errors included in i
Per: 1.30619 days
i:
82.15 +/- 0.21 °
fixed
1
81.77 -0.34|1.64+0.37|1.70 °
Planetary migration
Ou, Ji et al. (2007), ApJ
Kley et al. (2004), A&A
Close-in planets formation: a new mechanism
A new mechanism is revealed by which the collision–merger of planetary embryos can
kick terrestrial planets directly into orbits extremely close to their parent stars.
Ji, Jin &Tinney, 2011, ApJ
Kepler planets formation:
1:2:4 MMRs
The system of KOI-152
•
•
•
Final locations of three planets
Three planets are assumed to have
formed in the region away from the star.
Planets undergo type I migration. Three
planets are trapped into MMRs during
the migration.
tidal effects, arising from the central star,
circularize their orbits.
Wang, Ji & Zhou, 2012, ApJ
Evolution of three planets
Tidal evolution of Kepler-10 system
Dong & Ji, 2012, MNRAS
Time variations of a1 and e1 with various eccentricity pairs
a2 and e2 remain almost constant because of its far distance from the star
Numerical results are consistent with those from the general secular theory
Planet population synthesis coupled with evaporation
Left: Temporal evolution of a synthetic planet population
Right: Radius Distribution Compared with the Kepler Candidates
Evaporation could lead to a bimodal distribution in planet size
Jin et al. in prep
Planetary internal structure
We propose three possible internal
structure models for Europa.
Jin & Ji, 2012, Sci China-phys Mech Astron
Mass-radius relationship of terrestrial
plants and the Kepler detections.
Jin & Ji, in prep.
Constrain the planet structure
Lissauer et al. 2013, ApJ
From Wikipedia
•Find the possible structure of a planet in combination with the possible formation
scenarios.
•Does a planet have a atmosphere? Can the pressure and temperature at the bottom
of the atmosphere support liquid water?
TMT Science I: Primary eclipse and secondary eclipse
Transmission Spectrum, HD 189733b
Swain et al. 2008, Nature
•
Planet mass and radius are the only
information that we could get.
However, there is large degeneracy in
them (Valencia 2007; Seager 2007)
•
One possible way to break this
degeneracy is try to get the bulk
composition of the planet through
spectroscopy.
Thermal Emission, HD 189733b
Madhusudhan & Seager 2009, ApJ
Transit observations reveal a cloudy atmosphere
Kreidberg et al. 2014, Nature
Transit observations with the Wide Field Camera 3 (WFC3) show that the super-Earth planet
GJ 1214b may contain clouds in its atmosphere.
Featureless transmission spectrum of GJ 436b also suggests a cloudy atmosphere.
Knutson et al. 2014, Nature
TMT Science II: Direct Imaging
HR 8799 direct imaging planets detections.
Marios et al. 2008, Science; Marios et al. 2010, Nature
•
Obtain the luminosity and spectroscopic information of a planet.
•
Provide us clues about the atmospheric chemistry and composition.
•
Planet luminosity at young age could help us to distinguish how it is
formed, by core accretion (cold start) or by gravitational instability (hot
start).
Ongoing project in our group: atmosphere modeling and
spectroscopy
PT structure of HD 209458b:
Pressure-Temperature (PT) structure of HD
209458b. (Moses et al. 2012 ApJ)
PT structure of HD 209458b from our
calculation. For spectroscopy study, the
red p-T profile is used (nominal model).
Chemical abundance under thermochemical equilibrium:
Moses et al. 2012 ApJ
Calculation assuming solar abundances for the
chemical elements in planet atmosphere.
Moses et al. 2012 ApJ
Calculation assuming solar abundances for the
chemical elements in planet atmosphere.
Our work: a forward spectroscopy model
Emergent spectrum and observational data of HD 189733b. Moses et al. 2012, ApJ
For comparison, we superimpose our result, the green line, in this Figure.
The next step: Planet Atmosphere Retrieval
• First:
substitute
2-band
atmosphere profile with the nongrey model.
(Parmentier & Guillot 2013)
• Second: combine the MCMC
with our forward model to build
an atmospheric retrieval program.
(Madhusudhan & Seager 2009)
Best-fit after MCMC run
Modeled by Madhusudhan N.
TMT Science I I I : Habitable Planets
Planet with sufficient atmosphere that can support
liquid water on their surfaces.
About 5.7% stars have planets with
P = 200-400 d, Rp = 1-2 RE.
Kasting et al. 1993, Icarus
Petigura et al. 2013, ApJ
Petigura et al. 2013, PNAS
TMT ScienceＩＶ: 小行星直接成像？
采用光变曲线反演的方法获得了1996FG3的三维形状模型
采用已获得的7条光变曲线进行
反演
同时获得了该小行星的自转轴指
向为（237.70， -83.80）
与雷达图像比较显示：两者都存
在中间的隆起结构。
图中显示的是形状从四个不同的角度的图像
Arecibo获得的1996 FG3的雷达图像
TMT Ｖ: 小行星表面热物理性质研究
利 用 热 物 理 模 型 拟 合 Wolters et al
(2011)和Walsh et al (2012)公开的三
组中红外数据，得到了1996 FG3的
如下表面物理性质：
Summary
• Transit observations and spectroscopy study could reveal the atmospheric
feature and composition of close-in exoplanets (gas-giants, super-Earths
and Earth analogs ).
• Direct imaging will obtain the luminosity and the spectroscopic
information of a planet at large separations, especially at young ages.
• A lot of theoretical studies are required, such as atmospheric chemistry,
atmospheric circulation, spectroscopy and retrieval, radiation transfer, etc.
• TMT will definetely provide us a good opportunity to extensively
investigate exoplanets, understand the complexity and diversity of
planetary systems, to detect Earth-like planets in HZs.
Thank you for your attention!