recent developments of studies for transiting exoplanets
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Recent Developments of Studies for Transiting Exoplanets. Norio Narita National Astronomical Observatory of Japan. Outline. Introduction of Science of Transiting Exoplanets What’s New and What’s Going on Now? Near Future Prospects. Planetary transits. transit in the Solar System. - PowerPoint PPT PresentationTRANSCRIPT
Recent Developments of
Studies for Transiting Exoplanets
Norio NaritaNational Astronomical Observatory of Japan
Outline
• Introduction of Science of Transiting Exoplanets
• What’s New and What’s Going on Now?
• Near Future Prospects
Planetary transits
2006/11/9transit of Mercury
observed with Hinode
transit in the Solar System transit in exoplanetary systems(we cannot spatially resolve)
slightly dimming
The first exoplanetary transits
Charbonneau+ (2000)for HD209458b
Transiting planets are increasing
So far 69 transiting planets have been discovered.
Why are transits interesting?
We can characterize
origin, structure, and environment
of respective planets!
Scientific Subjects of TransitsOngoing• Mass-Size relation (structure)• The Rossiter-McLaughlin effect (origin)• Transmission Spectroscopy (environment)• Secondary Eclipses (environment)
Near Future• Transit Timing Variations• Exo-Rings and Exo-Moons
Mass-Size Relation
Charbonneau et al. (2006)
(too inflated)
HAT-P-3 b(heavy core)
TrES-4 b, etc
The Rossiter-McLaughlin effect
the planet hidesthe approaching side→ the star appears to
be receding
the planet hidesthe receding side
→ the star appears tobe approaching
planet planetstar
When a transiting planet hides stellar rotation,
radial velocity of the host star would have an apparent anomaly.
Transmission Spectroscopy
stellar linedimming with
excess absorption
upperatmosphere
planet
star
A tiny part of starlight passes through planetary atmosphere.
Secondary Eclipse
transit
secondary eclipse
Knutson et al. (2007)
transit
secondary eclipse
IRAC 8μm
provide information of thermal emissions of the dayside
Transit Timing Variations (TTV)perturbing but not transiting planet (or exo-moon)
orbit of transiting planetobserver observer
Exo-Rings and Exo-Moons
Taken by the Cassini spacecraft on September 15, 2006(Credit: NASA/JPL/Space Science Institute)
Summary of Recent News
1. Discoveries of transiting super earths
2. Discoveries of highly tilted transiting planets
3. Kepler launched and recently announced results
4. Possible Transit Timing Variations?
5. Discovery of the largest Saturnian ring
1: Discoveries of Transiting Super Earths
and their Meanings
First Transiting Super Earth CoRoT-7b
CoRoT-7b: Rp=1.7 Rearth Mp=4.8 MEarth
CoRoT-7: K0V star, d = 150 pcLeger et al. (2009), Queloz et al. (2009)
Second Discovery by MEarth Team
GJ1214b: Rp=2.68 REarth Mp=6.55 MEarth
GJ1214: M4.5V star, d = 13 pcCharbonneau et al. (2009)
Previous Mass-Radius Relation
Hartman et al. (2009)
inflated !!
HD149026
HAT-P-3
Diversity of Jovian Planets
Charbonneau et al. (2006)
(too inflated)
HAT-P-3 b(heavy core)
TrES-4 b, etc
New Mass-Radius Relation
Charbonneau et al. (2009)
Parameter space now comes to Earth-like region
H+He
pure H2O
H2O dominatedEarth-like
Diversity of Earth-like planets
2: Discoveries of Highly Tilted Planets
and their Meanings
Do Such Planets Exist?
Stellar Spin
Planetary Orbit
Semi-Major Axis Distribution of Exoplanets
Snow line
Jupiter
Eccentricity Distribution
Jupiter
Eccentric Planets
Standard Migration Models
consider gravitational interaction between
proto-planetary disk and planets
• Type I: less than 10 Earth mass proto-planets
• Type II: more massive case (Jovian planets)
well explain the semi-major axis distribution
e.g., a series of Ida & Lin papers
predict small eccentricities and small inclination for
migrated planets
Type I and II migration mechanisms
Migration Models for Eccentric Planets
consider gravitational interaction between
planet-planet (planet-planet scattering models)
planet-binary companion (Kozai migration)
may be able to explain eccentricity distribution
e.g., Nagasawa+ 2008, Chatterjee+ 2008
predict a variety of eccentricities and also misalignments
between stellar-spin and planetary-orbital axes
ejected planet
The Rossiter-McLaughlin effectreflects the trajectory of planetary orbit in front of stellar surface
well aligned misaligned(tilted)
Radial velocity during transits = Keplerian motion + Rossiter effect
Gaudi & Winn (2007)
1. HD209458 Queloz+ 2000, Winn+ 20052. HD189733 Winn+ 20063. TrES-1 Narita+ 20074. HAT-P-2 Winn+ 2007, Loeillet+ 20085. HD149026 Wolf+ 20076. HD17156 Narita+ 2008,2009, Cochran+ 2008, Barbieri+ 20097. TrES-2 Winn+ 20088. CoRoT-2 Bouchy+ 20089. XO-3 Hebrard+ 2008, Winn+ 200910. HAT-P-1 Johnson+ 200811. HD80606 Moutou+ 2009, Pont+ 2009, Winn+ 200912. WASP-14 Joshi+ 2008, Johnson+ 200913. HAT-P-7 Narita+ 2009, Winn+ 200914. CoRoT-3 Triaud+ 200915. WASP-17 Anderson+ 201016. CoRoT-1 Pont+ 201017. WASP-3 Simpson+ 201018. Kepler-8 Jenkins+ 201019. TrES-4 Narita+ to be submitted20. HAT-P-13 Winn+ to be submitted
Previous studies of the RM effectRed: EccentricBlue: BinaryGreen: Both
Summary of RM Studies
4 out of 7 eccentric planets have highly tilted orbits tilted planetary orbits may be common for eccentric planets
3 out of 13 non-eccentric planets also show tilted orbits spin-orbit misalignements are rare for non-eccentric planets
we can add samples to learn a statistical population of
alinged/misaligned/retrograde planets
2 out of 20 transiting planets show retrograde orbits
Distribution of spin-orbit alignment angles would be useful to
test planetary migration models
3: Kepler launched in 2009
and recently announced results
Beginning of the Kepler Era
Kepler launched on March 6, 2009
Just before the 5th Exoplanet Conference
in Kona
Kepler website
First result announced in August 2009
Kepler website
albedo
heat transfer
Kepler website
Kepler Started Exploration• large number of Jovian, Neptunian, Earth-like
planets will be discovered
Mass-Radius Distribution
Spin-Orbit Alignment Distribution
Albedo
Heat Transfer
Many theoretical studies will be stimulated!
By the way…
Kepler can determine transit times of transiting planets precisely.
What can we do with the Kepler data.
4: Observations of Transit Timing Variations
and Near Future Prospects
Transit Timing Variations (TTV)perturbing but not transiting planet (or exo-moon)
orbit of transiting planetobserver observer
Theoretical Studies• For another planet:
– Agol et al. (2005) / Holman & Murray (2005)
– a few min for a hot Jupiter having an earth-mass planet in 2:1 resonance orbit
– If an earth-mass planet exists around a hot Jupiter, even ground-based telescope would be able to detect TTV
• For exo-moon:– Kipping 2009a, 2009b, Kipping et al. (2009) – Exo-moons would be detectable with the Kepler
Likely First Discovery of TTV
Transit Epoch
01
-1-2
266 366 446
O-C
[m
in]
case of no TTV
Transit timing of OGLE-TR-111b (Diaz et al. 2008)
and TTV in this system is ongoing.
an Earth-mass planet in 4:1 resonant orbit?
Kepler will discover numbers of additional planets and exo-moons with TTV!
5: Discovery of the Largest Saturnian Ring
and Implication for Exo-Ring Exploration
Exo-Rings and Exo-Moons
Taken by the Cassini spacecraft on September 15, 2006(Credit: NASA/JPL/Space Science Institute)
Enceladus Earth
Methodology of Ring Detection• Transit light curves for ringed
planets are slightly different from those for no-ring planets
• Residuals between observed light curves and theoretical planetary light curves are ring signals
• Signals are typically ~10-4
level– Detectable with HST/Kepler
• We can learn configuration of rings with high precision photometryBarnes & Fortney (2004)
Discovery of the Largest Saturnian Ring
Verbiscer et al. (2009)(Credit: NASA/JPL
Caltech/Keck)
Largest ring extended
from 128 RSaturn to 207RSaturn
If we observe the Saturn as a transiting planet,differences of multiband transit light curves are quite large!
Characterization of Particle Size of Rings
• Diffractive forward-scattering depends on ring’s particle size and causes difference in depth of transit light
curve ramp just before and after
transits• Multi-wavelength
observations would be useful to characterize distribution of particle size
• SPICA’s wide wavelength coverage is useful to probe wide variety of particle size
Barnes & Fortney (2004)(for 0.5 micron observations)
Next Generation TelescopesJames Webb Space Telescope SPICA
after 2014 after 2018
Thirty Meter Telescope after 2018
Summary
Transit observations provide us
various interesting information to
characterize extrasolar planets!
Questions?