# Presentation: 338911

## Exoplanet Task Force

- Worlds Beyond: A Strategy for the Detection and Characterization of Exoplanets
*Final Report Briefing by*
*Jonathan I. Lunine, Chair*

- “Better is the end of the thing than the beginning thereof.”
*-Ecclesiastes*

## Task Force Membership

| Debra Fischer
San Francisco State  | Gary Melnick
CFA |
| --- | --- |
| Heidi Hammel
Space Science Institute | David Monet
USNO |
| Lynne Hillenbrand
Cal Tech | Charley Noecker
Ball |
| James Kasting
Penn State | Stan Peale
UCSB |
| Greg Laughlin
UCSC | Andreas Quirrenbach
Landessternwarte Heidelberg |
| Bruce Macintosh
Lawrence Livermore | Sara Seager
MIT |
| Mark Marley
NASA Ames | Josh Winn
MIT |

- Jonathan Lunine (chair) - LPL/University of Arizona

- Thomas Henning - MPI (ESA liaison)

## Task Force Process 

- Five Task Force meetings in 2007
- Public Input
- 18 external presentations
- 84 exoplanet white papers contributed from the community
- Open sessions during the first 4 meetings
- 7 external readers
- Report was reviewed by seven experts 12/07
- Report revised in response to the readers & submitted to AAAC 2/4/08.
- Final presentation to AAAC 2/11/08.

## Compelling Questions Identified by the Task Force

- What are the characteristics of Earth-mass/Earth-size planets in the habitable zone around nearby, bright stars?
- What is the architecture of planetary systems?
- How do planets and planetary systems form?

## Strategic Goals by end of time horizon

- To a high degree of statistical significance, η⊕should be determined around a broad range of main sequence stellar types.
- The architectures of planetary systems, both in the nearby solar neighborhood of order 106 cubic pc, and in the larger galactic bulge, should be constrained down to sub-Earth masses for semi-major axes out to several AU (for G-dwarfs)
- Provided  η⊕is large (at least 0.1), and exo-zodiacal emission typically low (< 10 zodis), at least one Earth-sized planet should have its mass and basic atmospheric composition characterized

## Recommendations: Towards Earths

**Intensify RV studies to reach down to (several) Earth-mass planets around bright stars**
- More telescope time/higher precision
- Invest in IR spectrograph development for late M stars
**Search for transiting terrestrial-size exoplanets around nearby M dwarfs and characterize with Warm Spitzer and JWST**

## Recommendations: Towards Earths

**Develop a space-borne astrometric planet search mission**
- Mass and orbits are required to understand habitability
- Find the Earth-mass exoplanets in habitable zones of nearby sun-like stars and get their orbits
- Sub microarcsecond astrometric signatures on order of 100 stars
- Study planetary architectures whether or not Earth-mass planets are common, whether or not zodi is large
**Prepare for space-based direct imaging characterization mission**
- Ongoing development to be ready for launch after some targets are known
- Exozodi measurements down to 10 zodi around nearby stars

## Recommendations: Planetary Architectures/Formation

**Microlensing for planetary masses and separations **
- Augment ground-based facilities
- Space-based mission if possible at Discovery level or below, if does not affect the astrometric and direct imaging missions
**Ground-based direct imaging**
- Develop and implement extreme AO
- Support construction of a 30-m telescope with extreme AO

## Recommendations: Planetary Architectures/Formation

**Circumstellar Disk Science**
- Maintain US involvement in Herschel and ALMA
- Archival analysis for relevant Spitzer, Chandra, Hubble, and ground-based data
- Invest in appropriate instrumentation on large-aperture telescopes
**Support for activities that maximize the knowledge return from data and train new scientists in the field**
- Theoretical studies
- Stellar property surveys
- Competitive fellowships for young researchers

## Two-Pronged Strategy

- Prong 1: M dwarfs

- Prong 2: F, G, K dwarfs

## If  η⊕ is > 0.1

-         ,masses, addresses   Density, detectability      Characterize for habitability

- M dwarfs

- F, G, K dwarfs

- Density, addresses                   Characterize for habitability

- Exo-zodi studies

- If  η⊕ is > 0.1

*RV  +  Transit surveys--*> Spitzer-->JWST

- Corot/ Kepler   *--*> Astrometry+RV  --> Space Direct Imaging

## If  η⊕ is < 0.1

-         ,masses, addresses   Density, detectability

- M dwarfs

- F, G, K dwarfs

- Planetary Architecture

- Exo-zodi studies

- If  η⊕ is < 0.1

*RV  +  Transit surveys*

- Corot/Kepler              Astrometry
-                                 Microlensing

- Ground-based EXAO on ELT for giant planets

- Larger space-based system

## If  Exozodi > 10 Earth Zodi

-         ,masses, addresses   Density, detectability      Characterize for habitability

- M dwarfs

- F, G, K dwarfs

- Planetary architecture

- Exo-zodi studies

*RV  +  Transit surveys--*> Spitzer-->JWST

- Corot/ Kepler   	Astrometry

- Microlensing

- Ground-based EXAO on ELT for giant planets

**Notes:**
A 

We always 14
A 37

## Recommended Programs, Missions and Activities

-    Advanced and intensive RV studies - Kepler followup
-                  Advanced ground-based microlensing
-                                Advanced ground-based transit searches
-                                                              ELT advanced imaging (extreme AO)

- Technology development

- Discovery Microlensing Mission

- Spitzer transit followup

- JWST transit followup

- Kepler

- Astrometric mission

- IR Characterization

- Visible Characterization

- Ground-based

- Existing Missions

- Proposed Missions

- Exozodi characterization, lab, theory, fellowships, other supporting data

## Strategy Summary

**Two-pronged approach**
- Potential for early results on Earth-sized planets orbiting M stars
- Astrometric search is insensitive to zodi and background objects; ensures significant results on planetary architectures and Earth-mass planets
- Known targets simplify the space-based direct detection mission
**Flexibility**
- Decision points occur early enough in the strategy to shift focus toward the end, contingent on η⊕and zodi
- Individual elements can be delayed or stretched out while the overall program still provides exciting discoveries

## Reader comments & responses I

- N.B. No reader challenged the fundamental strategy.
*Hinging the strategy on a space-borne astrometric mission requiring 0.2 μarcsec is risky*
**The TF reviewed this very carefully and we conclude that the astrometric goal is challenging but achievable. Our recommendations include early non-advocate, expert review of spaceborne astrometric technology. **
**A modified approach could proceed without astrometry, but it is much riskier and leaves us without knowledge of the mass and orbit data. **
*Completeness figures should be plotted in universal axes. *
***Done***

## Reader comments & responses II 

*The detailed discussion of techniques is too lengthy for the report’s readership*
**We have relegated this discussion to an appendix, while moving its key material up front to a beefed-up summary of techniques.**
*There was a bias in favor of coronagraphy as pposd to interferometry as the first direct detection mission, *
***The Task Force believes that coronagraphy or the external occulter are more mature than interferometry for this application. However, we have rebalanced the discussion and added a recommendation that more effort be put into determining the technical maturity of each. ***

## Slide 18

## Depth of Search Figures

- The number of detectable planets assuming every star to be examined has a planet of the given mass and semi-major axis
- No assumptions need be made about planet distributions
- No imposed mission lifetime
- Scaled x-axis allows all star types on the same plot
- Both x- and y-axes are on a log scale

## RV Studies

- Optical

- Near IR

## Terrestrial Transits for Characterization

- Transits from space

- Atmospheres with JWST

## JWST transit studies (M -dwarfs only)

## Kepler

## Space-Based Microlensing

## Space-based microlensing

## Space -based Direct Imaging

- Space -based Direct Imaging

## Ground-Based Direct Imaging

## Issue of cost

- There are three new missions within the 15 year time horizon, two of which are essential (of which one can be stretched out).
- Key to costing is early, intense technology studies and blue ribbon reviews on cost, risk.

## Recommended Programs, Missions and Activities

-    Advanced and intensive RV studies - Kepler followup
-                  Advanced ground-based microlensing
-                                Advanced ground-based transit searches
-                                                              ELT advanced imaging (extreme AO)

- Technology development

- Discovery Microlensing Mission

- Spitzer transit followup

- JWST transit followup

- Kepler

- Astrometric mission

- IR Characterization

- Visible Characterization

- Ground-based

- Existing Missions

- Proposed Missions

- Exozodi characterization, lab, theory, fellowships, other supporting data

## Conclusions

- Are there habitable planets around other stars?
- What is the architecture of planetary systems?
- How do planets fit in to the process of star formation?
**2. The plan provides the opportunity for early discoveries and risk reduction; spaceborne direct imaging is significantly simplified**
**3. Plan depends on a balance of ground and space; existing and future assets**
**4.** **Plan is flexible to surprises, failures and new discoveries**
**5. Plan is already streamlined in cost but can be stretched out**

## I personally want to thank

- The Task Force
- The AAAC
- The Readers
- All of our NASA and NSF experts
- The community
*but especially....*
- Dana Lehr
- Stephen Ridgeway
- Garth Illingworth