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星形成・惑星・太陽系班報告
TMTによる太陽系外惑星の探究
成田憲保（国立天文台）
＆星形成・惑星・太陽系班メンバー
＠TMTサイエンス検討報告会
星形成・惑星・太陽系班活動報告
グループ会議履歴
第1回 5月14日(金) 08:15-10:00 三鷹解析棟+TV-con
議題：班員紹介、検討班の方針とスケジュール決定、
第2回 6月14日(月) 08:00-10:00 三鷹解析棟+TV-con
議題：サイエンストピックスの決定と分担
第3回 8月 5日(木) 13:00-18:00 三鷹解析棟
議題：班員によるサイエンス検討状況発表
第4回 12月 10日(木) 13:00-18:00 三鷹解析棟
議題：報告書原稿の確認とフィードバック
星形成・惑星・太陽系班キャッチフレーズ
“星と惑星の誕生、そしてその環境に迫る”
Science Group Members
Star/Planet Formation
•
•
•
•
•
•
•
•
•
•
•
T. Fujiyoshi
M. Fukagawa
S. Hirahara
M. Honda
S. Inutsuka
T. Muto
H. Nomura
Y. Oasa
T. Pyo
Y. Takagi
M. Takami
Exoplanets
•
•
•
•
•
T. Matsuo
N. Narita
B. Sato
T. Sumi
T. Yamashita
Solar System
• Y. Kasaba
• T. Sekiguchi
• T. Terai
Science Topics of Star Formation
1. Search for new interstellar molecules by high-dispersion Mid-IR
spectroscopic observation
2. Initial Mass Function (IMF), Masses and Ages of Young Stars
3. The Solution to The Angular Momentum Problem in Star Formation:
Jets and Outflows from Young Stellar Objects
4. High Mass Star Formation
Science Topics of Planet Formation
1. Observation of the Detailed Morphology of Circumstellar Disks
2. Observations of the Spatial Distributions of Dust and Ice Grains in
the Protoplanetary Disk
3. Mapping the magnetic field in the circumstellar disks by MIR
polarimetry
4. Observations of H2 Line Emission to Probe Gas Dispersal
Mechanism of Protoplanetary Disks
5. Spatial Distribution of Organic Molecules in Protoplanetary Disks
Science Topics of Exoplanets
1. Exoplanet Searches with Precise RV Method
2. High resolution spectroscopy of exoplanet biomarkers at transits
3. Search for Biomarkers in Habitable Exoplanet Atmospheres by
Multi-Object Spectroscopy
4. High Dispersion Spectroscopy of Sodium Atmospheric Absorption in
Exoplanet Atmospheres
5. Uncovering Migration Mechanisms of Earth–like Planets by the
Rossiter-McLaughlin Effect
6. Direct Imaging Survey of Terrestrial Planets in Habitable Zone
7. Study of Exoplanet Distribution by Identifying the Host Stars of
Planetary Gravitational Microlensing Events
8. Direct imaging and low resolution spectroscopy of exoplanets in the
mid-infrared
Science Topics of Solar System
1. High Spatial Resolution Imaging for Small Solar System Bodies and
Dwarf Planets
2. High Spatial Resolution Imaging for Planets and Satellites
3. High Spectral Resolution Spectroscopy of Atmospheres of Planets
and Satellites
Exploring (Earth-like) Exoplanets
• RV search for new low-mass planets
• Transit follow-up studies
• Gravitational microlensing follow-up studies
• Direct imaging studies
Exoplanet Searches with Precise RV Method
• Precise Radial Velocity Measurements
– High-dispersion spectrograph with very precise wavelength
calibration is required
– Ultimate precision depends on S/N of stellar spectrum
• Huge aperture of TMT enables us to
– observe faint stars with high S/N
– Targets: low-mass stars, stars in clusters, microlense objects,
etc.
– observe relatively bright stars with ultra high S/N (ultra
high precision)
– Targets: solar-type stars, giants and subgiants, early-type
stars etc.
Detecting Earth-mass Planets in HZ
RV semi-amplitude of host stars by companions in HZ
Infrared preferred
red solid
Optical preferred
blue dashed
10ME
5ME
3ME
2ME
1ME
M6
M5
M0 K0
G0 F0
Detecting Earths around Solar-type Stars by
Optical-RV Method: Targets
• ESO 3.6m+HARPS-type
– 3800-6900Å, R=115,000, Simultaneous Th-Ar method
– Texp=900s, σ=1m/s  mv~10
• Subaru 8.2m+HDS-type
– 5100-5700Å, R=100,000, Iodine Cell
– Texp=900s, σ=1m/s  mv~10
• Texp=1800s, σ=0.1m/s
–
–
–
–
–
ESO(3.6m)+HARPS-type  mv~5--6
VLT(8m)+HARPS-type  mv~7.5
E-ELT(42m)+HARPS-type  mv~11
Subaru(8.2m)+HDS-type  mv~5--6
TMT(30m)+HDS-type  mv~8.5
At least ~1800 s exposure is
required to average out
stellar p-mode oscillation
down to <0.2 m/s level
(Mayor & Udry 2008)
Searching for Habitable Earths around
M Stars by IR-RV Method: Targets
Data from Lepine et al. (2005)
400
400
Mv=130.3M 
300
Subaru
1630 stars
250
5<=J<10
200
150
Mv=16
0.1M 
100
50
0
350
Number of stars
Number of stars
350
2871 stars
300
250
5<=J<12
200
150
100
50
0
8
9
10
11
12
13
14
15
16
17
18
19
20
8
9
10
11
12
13
MV
15
16
17
18
19
20
MV
400
400
2534 stars
300
250
5<=J<11
200
150
100
50
TMT
350
Number of stars
350
Number of stars
14
3039 stars
300
250
5<=J<14
200
150
100
50
0
0
8
9
10
11
12
13
14
MV
15
16
17
18
19
20
8
9
10
11
12
13
14
15
16
17
18
19
MV
TMT has many target stars for which we can search for habitable earths.
20
Planetary Transit Follow-up
• Transmission spectroscopy
– method to observe exoplanetary atmospheres
• high spectral resolution (HROS, NIRES, etc)
• MOS (WFOS/MOBIE, IRMOS etc)
• Rossiter effect
– method to observe exoplanetary orbital tilts
• precise RV measurements during transits
Transmission Spectroscopy
star
One can probe atmospheres of transiting exoplanets by
comparing spectra between during and out of transits.
Targets and Methods
• Target Stars: Earth-like planets in HZ
– M stars: favorable
– Solar-type stars: difficult
• Target lines
– molecule lines in NIR
– oxygen A lines
– sodium D lines
• Methods
– High Dispersion Spectroscopy
– Multi-Object Spectroscopy
Rossiter effect of transiting planets
star
planet
planet
the planet hides an approaching side
→ the star appears to be receding
the planet hides a receding side
→ the star appears to be approaching
One can measure the obliquity of the planetary orbit
relative to the stellar spin.
The obliquity can tell us orbital evolution mechanisms of exoplanets.
What we learned from the Rossiter effect
 For Jovian planets, tilted or retrograde planets are not so rare
(1/3 planets are tilted)
 How about low-mass planets?
Detectability of the Rossiter effect
Current
Opt. RV
Subaru
IR RV
TMT IR
(1m/s)
TMT opt.
(0.1m/s)
F, G, K
Jupiter
○
○
○
○
F, G, K
Neptune
△
△
○
○
F, G, K
Earth
×
×
×
○
M
Jupiter
△
○
○
○
M
Neptune
△
○
○
○
M
Earth
×
△
○
△
○：mostly possible, △：partially possible, ×：very difficult
Planetary Microlensing Follow-up
Ground-based surveys (e.g., OGLE,
MOA) and future space-based
survey (e.g. WFIRST) will find
many planets via this method
Planet Distribution
•RV
•transit
•Direct image
•Microlensing：
Mass measurements
Mass by Bayesian
Only half of planets have
mass measurements.
Need to resolve lens
star to measure lens
and planet’s mass!
TMT can resolve source and lens star
Average relative proper motion of lens and source star: μ=6±4mas/yr
Resolution:
•1.2x2.2μm/8.2m= 66mas
(~80mass in VLT/NACO and Keck AO)
•1.2x2.2μm/30m=18mass
Required time to separate by 2×psf:
8.2m: T8.2= 22+44-9 yr
30m: T30 = 6+12-2 yr
Direct Imaging
• TMT/PFI can resolve outer side of planetary systems
• Also, TMT may be able to detect a second Earth
around late-type stars -> Talk by Matsuo
使いたい観測装置
• 可視高分散分光器 (HROS) ４
• 近赤外高分散分光器 (NIRES) ３
• 高コントラスト・高空間分解能撮像装置 (PFI/SEIT) 2
• 広視野可視多天体分光器 (WFOS-MOBIE) １
• 広視野撮像装置 (WIRC) １
• 広視野近赤外多天体分光器 (IRMOS)
• L バンド分光・撮像装置
日本の独自性と戦略
• TMTの本格稼働前にすばる望遠鏡などでどれだけ独自のター
ゲットとなる惑星を発見できるかが重要
•
すばる望遠鏡IRDによる視線速度サーベイ
•
MOAによるマイクロレンズサーベイ
•
岡山などでのトランジットサーベイ
• すばる望遠鏡で木星型・海王星型惑星に対する観測を進め
TMT稼働後すぐに地球型へ挑戦
• 観測提案の土台となる方法論の確立・スキル・結果が大事
まとめ
• 系外惑星に対するサイエンスは、視線速度・トラン
ジット・マイクロレンズ・直接撮像からそれぞれ提案
された
• TMTの集光力、空間分解能、新装置によって、より
小さくて軽い系外惑星（＝地球型惑星）の研究への
ブレイクスルーが期待される

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