A Roadmap for Exoplanets

The ExoPlanet Roadmap Advisory Team

(EP-RAT)

The EPRAT

Artie Hatzes, (Chair), Thüringer Landessternwarte, Germany Anthony Boccaletti, Observatoire de Meudon, France Rudolf Dvorak, Institute for Astronomy, University of Vienna,

Austria Giusi Micela, INAF - Osservatorio Astronomico di Palermo, Italy Alessandro Morbidelli, Observatoire de la Cote d'Azur, France Andreas Quirrenbach, Landessternwarte, Heidelberg, Germany Heike Rauer, German Aerospace Center (DLR), Germany Franck Selsis, Laboratoire d'Astrophysique de Bordeaux (LAB),

France Giovanna Tinetti, University College London, UK Stephane Udry, Université de Genevé, Switzerland Anja C. Andersen, Dark-Cosmology Center, Copenhagen, Dk (Expert)

Malcolm Fridlund, (Secretary), ESA

The EPRAT was formed to:

EPRAT is to advise ESA on the best scientific and technological roadmap to pursue in order to address the characterization of terrestrial exo-planets (up to the possible detection of biomarkers)

The Roadmap

Things to Keep in Mind

• The Roadmap is just a draft and is by no means the final product. If you do not like it, now is the time to speak!

• The EP-RAT is merely an advisory board to the community as a whole and not just to ESA. ESA does not propose missions, the community does

• Like all roadmaps this one will be outdated in a few years

“Yeah, well, you know, that’s just, like, your opinion, man.“

Jeffery Lebowski „The Big Lebowski“

• It is our opinion and we bring our own biases to the roadmap

Things to Keep in Mind

The EPRAT does not:

• Propose missions, we propose science and a suggest directions the field should go

• „Bless some missions over others“

• Replace the peer review process: proposals for space missions come from the community and we are not the ones evaluating these

Things to Keep in Mind: Budget Landscape

Bleak

Depressing

Should we become truck drivers?

Things are bad, and are not expected to get better in the next 10-15 years.

Large flagship missions may have gone the way of the dinosaurs, for now.

8

Approximate Timeline and Definitions

Near term: ~2011-2017:

Long-term: ~2020 and beyond

Mid-term : ~2015-2022:

We know what we want to learn and we know how to do it.

We know what we want to learn and we think we know how to do it.

We think we know what we want to learn but we are not quite sure how to do it.

Milestones range from detection through characterization:

• Architecture: multiple planets, accurate orbital elements

• Mass, radius, and mean density of exoplanets• Spectroscopic features of exoplanetary

atmospheres• Exo-magnetospheres• Possible biosignatures.

Milestones for the Roadmap

• What is the diversity and architecture of exoplanetary systems?

• What is the diversity of composition, structure, and atmospheres?

• What is the origin of the diversity and how do planets form?

• What makes a planet habitable?• Can we detect exo-life and if so, how

common is it?

Key Questions

We want to do comparative Exoplanetology

Short period high mass → Short period low mass →

Long period high mass → Long period low mass →

The Path of Discovery Space

The Path of Characterization

Moderately Easy

Difficult

Easy

Very Difficult

Easy

Very Difficult

Moderately Easy

Forget it1

1Radius and mass comes from evolutionary tracks

Caveat: Characterization requires a discovery

Ground

CoRoT

Kepler

mostly

Kepler

PLATO

2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025

Kepler

CoRoT

GAIA

VLTI:PRIMA

Keck: ASTRA

Space Interferomertry Mission

HST

(Warm) Spitzer)

Herschel

James Web Space Telescope

PLATO

30 Meter Telescope and Giant Magellan

SPICA

Extreme Adaptive Optics on ELTs

Transit Survey Missions

Spectroscopy

Astrometry

LOFAR

SKA

ESA CV2: M-Class

NASA Explorer Probe

NASA ExplorerCompetitive Mission Opportunities

Long Wavelength facilities

ALMA

European Extremely Large Telescope

Imaging and

Large Binocular Interferometer

Planet Finders (Large Tel.)

N2: Radial velocity monitoring of several thousand nearby F-K main sequence stars and evolved, intermediate mass stars using optical spectrographs. OPTICAL SURVEYS

Detection: Radial Velocities

• Statistics as a function of stellar parameters (mass, abundance, binarity, etc)

• Targets for characterization

N3: RV Planet Searches in the Infrared with emphasis on short-period, low-mass planets around M dwarfs. INFRARED SURVEYS

• Atmospheric characterization of terrestrial planets in a habitable

zone of a planet will most likely be done on M dwarfs• Targets for characterization • Planet formation around low mass stars• Planet confirmation

N4: Terrestrial planets in the habitable zone of G-type stars: High cadence monitoring of a sample of 50-100 G-type stars with low levels of activity.

• Improved wavelength calibration (e.g. Laser Frequency Combs)

• Lots of observations (beat down oscillations and activity noise)

• Superearths and possibly earth-mass in habitable zone of G-type stars are detectable with RVs

• Targets for characterization

M13 Obtain a sample of Terrestrial planets in the Habitable Zone of G-K type stars

Detection: Radial Velocities

N6: Continued RV monitoring of all known exoplanet hosting stars in order to investigate the architecture of exoplanetary systems and to derive accurate orbital parameters.

Don‘t forget to keep monitoring the known exoplanet hosting stars:

• If a star has one planet it probably has several. We need to understand this architecture

• Accurate orbital parameters are needed for dynamical studies (stable planets in habitable zone), accurate ephemeris needed (transit searches even for long period planets)

M5: Continue long term RV surveys to find planets at large orbital distances, multiple systems, and to refine orbital parameters of known exoplanets.

N5: A Search for Planets Among Stars in Diverse Environments

• The role of environment for planet formation is still poorly known

• Planet searches in clusters, binary stars, young stars, etc.

Detection: Radial Velocities

M10: Use of ALMA to study exoplanets in their birth environments

N7: Securing the necessary telescope resources

• Dedicated facilities (4-8m class telescopes) for RV

measurements.

• Inclusion of small telescopes in the effort. Ideal niche for

small, underutilized 2-4 m class telescopes.

• Coordinated search activities: Workshops and working groups

• Increased funding at a National and European level.

Detection: Radial Velocities

M12: Astrometric Searches for Terrestrial Planets with SIM-lite

Detection: Astrometry

• One goal of SIM-lite is to detect terrestrial planets in habitable zone of G-type star

• Targets for future characterization missions

M11: True mass determination of known giant planets with GAIA: Deriving the true mass function for giant exoplanets..

The most fundamental property of a planet is its mass. The true mass only comes from transiting planets, or astrometry.

Detection: Microlensing

N15: Continue ground-based microlensing searches

• Probes the low-mass planet regime

• Can give statistics

Note: Microlensing searches most likely cannot produce targets for future characterization studies

Do not recommend a dedicated microlensing space mission, but „piggy-back“ would be good.

N13: Increase the sample size of pulsar planets

Detection: Pulsar Planets

• We know very little about pulsar planets due to the very small number statistics

• Every type of planet helps in our understanding of planet formation.

• We need to find more milli-second pulsars (LOFAR)

N16: Make Effective use of Planet finders for Exoplanets Studies

Detection: Angularly Resolved Detections

• Ground-based telescopes (VLT, Gemini and Subaru) will soon (2011) be equipped with “planet-finders” (SPHERE, GPI and HiCIAO) making use of extreme adaptive optics, achromatic coronagraphy and differential imaging. These instruments will achieve contrasts of 106 to 108 in the near IR and will be able to probe the region within 5-10 AU to search for giant planets.

M6: Continue direct imaging studies from the ground (AO, coronography) to find large planets at large orbital distances.

Characterization: Structure (M, R)

N9: Optimizing ground-based transit searches

• Focusing on bright stars. Ideal for characterization studies.• A search for transiting low-mass planets around M dwarfs (e.g

MEarth project). Targets for Herschel, JWST, or future spectral characterization missions.

• A search for transits for planets found by the RV method, including long period systems.

• A search Transit timing variations (TTVs) and transit duration variations (TDVs).

M7: Keep facilities to determine radii of transiting planets found by RV surveys and to search for transit timing and transit duration variations.

N10: Continuation of the CoRoT and Kepler past the nominal mission life

• We are lucky to have 2 exoplanet space missions flying. We should keep them going as long as possible

• Possible modest support from ESA?

Characterization: Structure (M, R)

Characterization: Structure (M, R)

N14: Ground-based support of CoRoT, Kepler, and preparation for ground-based support for GAIA.

• Lesson from CoRoT and Kepler: There can be insufficient telescope resources for support. For PLATO this essential for science goals. Organization of ground-based support should start as soon, if not sooner, PLATO is approved.

• ESA support (in words if not resources) is important

• Prepare for follow-up of Gaia detections. 1) High-resolution, high-precision spectroscopy of Gaia-discovered systems, 2) Direct imaging campaigns (SPHERE/VLT,EPICS/E-ELT) will complement astrometric detections.

M3: Secure the ground-based support necessary for follow-up of PLATO transit candidates

Characterization: Structure (M, R)

M2: Transit Searches for Small Planets around solar-type stars

• This will require PLATO or TESS

Characterization: Atmospheres

N17: Effective use of JWST for Exoplanets Studies (spectral characterization, imaging, photometry, phase curves, colors)

• JWST will a valuable facility for performing characterization studies of exoplanets,

• General Purpose facility → few targets

• European scientists get a small amount of time

• The community must move fast and organize itself so as to effectively use its small share of the time effectively on exoplanet studies.

M8 Devote time on ELT and JWST for key programs for in transit spectroscopy of transiting planets and direct imaging of Giant planets at large orbital distances.

Characterization: Atmospheres

N8: Characterization of Transiting Planets in the visible and IR with ground-based and on-going space based facilities

• Basis for planning of future space missions

Characterization: Magnetospheres

N12: A search for radio emission from exoplanets with LOFAR

L4: Use SKA for the detection of radio emission from exoplanets

Characterization: Theory + Observations

N21: Calibration of giant planet evolutionary tracks

• The nature of „planetary“ companions at wide (a>100 AU) orbital distances and „free floating planets“ is unknown until you get the mass

• When it comes to masses I trust Kepler and Newton

• If you have calibrated these tracks, then we may believe your mass determination.

Characterization: Atmospheres

N19: Theoretical studies on the spectroscopic signatures expected from exoplanets covering a wide range of masses (terrestrial to giant planets) and a wide range of temperatures.

If we want to do characterization of exo-atmospheres we need to know:1. Spectral features2. Spectral Coverage3. Spectral Resolution4. Minimum Signal-to-Noise ratio requirements5. Exposure times6. Required Instrumental Stability

If you are going to propose a space mission do you homework!

Characterization: Atmospheres

M1. Preparation for an M-class and/or smaller mission for characterization of exoplanet atmospheres from gas giants to superearths

Characterization of a large sample exoplanet atmospheres is major next step in exoplanet studies

Transiting planets: The spectral investigation of Hot Jupiters, Hot Neptunes, and Hot Superearths using in-transit spectroscopy and radiated light (secondary eclipse).

Angular Resolved Detections. Mature giant planets to Superearth at distances > 1 AU from the host star.

Note: at some point we will need both!

Characterization: Atmospheres

1. Technological feasibility in the time frame of the proposed mission.

2. Suitable sample of target stars

3. Scientific return

4. Cost that can be accommodated in the current ESA budget

The type of mission that will fly first depends on:

Note to proposers, examine 2 options:• A small mission with a total cost of ~200 Million Euros

and with reduced science objects.

• A medium class mission with a total cost of ~400 Million Euros with larger sample and more ambitious goals.

Technology

N18: Technological studies for Angularly Resolved Detections

Possible direct imaging techniques:

1. Coronography2. Nulling Interferometry3. Fresnel Interferometers4. Occulters5. Fancy new future technology

It is not clear which is the best one to use for a future flagship mission to characterize terrestrial planets around G-K stars. This must be determined beforehand.

M9: Continued technological Research & Development studies into the various Angularly Resolved Detections.

Habitable exoearths

Don‘t forget the stars!

N1: Stellar studies of all stars out to 50 pcs: understanding the host stars of exoplanet systems, statistics as a function of stellar properties.

N20: An investigation of the influence of stellar activity on habitability and anticipated atmospheric signatures

• The habitable zone of an M-dwarf is habitable in an extreme sense of the word.

• M dwarfs have high X-ray fluxes, CME, etc

M4: Obtain accurate stellar parameters using GAIA and PLATO

Long term Recommendations

If there really is a Santa Claus:

L1: Begin work on a flagship mission to characterize all the known terrestrial planets in the habitable zone of F-K type dwarfs.

• Building on the scientific and technological experience from the near- and mid-term

• Know what technology to employ

• Know what targets to look at

L5: Planning and technological development for the construction of Mega-telescopes

L6: Technological studies for extreme adaptive optics with Mega-telescopes

Long term Recommendations

2. Recommend a atmospheric characterization mission. We have discovered a lot of planets, but characterization across the parameter space is lacking. Internal structure characterization is well covered by CoRoT, Kepler, and hopefully PLATO

• Short period transiting systems (1st and 2nd transit) of G-M dwarfs

• Warm/cool planets with direct imaging

Note: this is a case of „one then the other“ not „either or“ → need to explore the full parameter space

Recommendations to ESA

1. Open Time Key Program on JWST for Exoplanets

• Europe has very little time on JWST the exoplanet community needs to use this effectively

4. Talk to ESO, find a European solution to the ground-based support of space missions. We will need this for PLATO.

• Outright purchase of telescope time?

• ESO devote a fraction of telescope time to space support with its own panel and peer review process

3. Give us more options. If ESA and NASA (or other countries) can only fund small missions it makes sense to pool resources

• Make the interface work

Recommendations to ESA

5. „Support“ technology studies at university and national laboratories (G5)

• Technology breakthroughs often come at universities or national laboratories, but these lack the technical expertise for porting a system to space.

• Consultations?

• Take on „internal design studies“?

Recommendations to ESA

6. SIM-lite: NASA may becoming with hat in hand

Recommendations to ESA

• If NASA needs a „small“ amount of money (100-200 MEuros) EPRAT supports joining so long as it does not impact other programs

• But… if it is a substantial amount (500 MEuros) this will seriously impact other missions and community should give careful thought

→ in either case this should be a formal proposal from the European community that goes through the peer review process

7. Coordination with national space agencies and possible support on small missions.

Recommendations to ESA

• ESA had a small contribution to CoRoT which was money well spent.

• Similar support or coordination for technology missions.

General Recommendations

G1: Stronger International Cooperation

• Budget situation is bad everywhere, we will need friends

• Look towards „non-traditional partners“ (China and India)

G2: Laboratory measurements to produce line lists, atomic and molecular transition probabilities, opacities, and equation of states, dust properties

G5: Involve the Planetary Community

• The field is still dominated by astronomers

- A community that can help support your next mission

- Bi-annual meetings in the “Cool Stars” or “Protostars and Planets” → “Exoplanets, Planetary Systems, and the Solar System”

General Recommendations

G6: A Rigorous Public Outreach

• Taxpayers ultimately fund space missions we need to keep them interested

• ESA can learn much from NASA

• „Grassroots“ Efforts

G7: Keep a vibrant community going

“… the torch has been passed to a new generation..”Inaugural address, John F. Kennedy

• Keep this an exciting and vibrant field with a pool of talented young scientists

• Don’t plan something where the scientific result is 20 years in the future, you will lose the best and the brightest.

• Keep exciting new results coming so as to attract young scientists.

Final Remarks

1. We may get just one mission after PLATO. Think carefully what you want

2. Have broad community support for the mission

3. Make a good case that it can only be done from space

Can it be done from the ground ?

Are you adding substanitally more targets/science than JWST can provide

Final Remarks

4. For characterization missions you better have your targets before hand, or a good ideas as to how you will get them.

5. Think small, it has a better chance of getting funded; but

RV < 0.1 m/s precision

Photometric precision ~ 10–5

Astrometric precision < 1 as

Contrast ratios of 10–9 to 10–10

Probably not small and definitely not cheap!

Final Remarks

6. Speak with a unified voice.

"We must all hang together, or assuredly we shall hang separately."

Benjamin Franklin