Scott Gaudi

Matthew PennyThe Ohio State University

Exoplanet Science with

WFIRST-AFTA

Microlensing 18

Kepler is revolutionizing our understanding of exoplanets here!

Ground-based Surveys.• Ground-based surveys

only sensitive to masses greater than ~Mearth.

• Narrow range near near peak sensitivity, roughly 1-4 times the snow line.

• Only sensitive to giant free-floating planets.

Earth Mass and Below?

• Monitor hundreds of millions of bulge stars

continuously on a time scale of ~10 minutes.– Event rate ~10-5/year/star.

– Detection probability ~0.1-1%.

– Shortest features are ~30 minutes.

• Relative photometry of a few %. – Deviations are few – 10%.

• Main sequence source stars for smallest planets.

• Masses: resolve background stars for primary

mass determinations.

Ground vs. Space.• Infrared.

– More extincted fields.– Smaller sources.

• Resolution.– Low-magnification events.– Isolate light from the lens star.

• Visibility.– Complete coverage.

• Smaller systematics.– Better characterization.– Robust quantification of

sensitivities.

SpaceGround

The field of microlensing event

MACHO 96-BLG-5

(Bennett & Rhie 2002)

Science enabled from space: sub-Earth mass planets, habitable

zone planets, free-floating Earth-mass planets, mass

measurements.

History.• NASA Proposals (GEST/MPF) – PI David Bennett.

– Submitted to Midex in 2001, Discovery in 2000, 2004, 2006

– Not selected.

• Decadal Survey White Papers:– Bennett et al. “A Census of Exoplanets in Orbits Beyond 0.5 AU via Space-based Microlensing”

– Gould, “Wide Field Imager in Space for Dark Energy and Planets”

• Wide-Field Infrared Survey Telescope (WFIRST).– Top Decadal Survey recommendation for a large space mission (Dark Energy, Exoplanets, Galactic

Plane, GO Program)

– Science Definition Team – DRM1 and DRM2

– No funding until JWST is launched (~2017).

• National Reconnaissance Office (NRO) telescopes.– Two 2.4m space-qualified telescopes, donated to NASA.

– Mirrors and spacecraft assemblies.

– SDT formed to assess use for WFIRST, consider a coronagraph and serviceability.

• Euclid.– ESA M class Dark Energy Mission

– Microlensing is not part of the core science.

WFIRST-2.4

AFTA-WFIRST

Eff. Aperture 2.28m

FOV 0.281 deg2

Wavelengths 0.7-2 μm

FWHM@1μm 0.10”

Pixel Size 0.11”

Lifetime 5 years +?

Orbit Geo (?)

Wide-Field Instrument

• Imaging & spectroscopy over 1000's sq deg.

• Monitoring of SN and microlensing fields

• 0.7 – 2.0 micron bandpass

• 0.28 sq deg FoV (100X JWST FoV)

• 18 H4RG detectors (288 Mpixels)

• 4 filter imaging, grism + IFU spectroscopy

Coronagraph (descopeable)

• Imaging of ice & gas giant exoplanets

• Imaging of debris disks

• 400 – 1000 nm bandpass

• 10-9

contrast

• 200 milli-arcsec inner working angle

Comparing Designs.

Euclid (Opt/NIR)

WFIRST DRM1

WFIRST DRM2

AFTA-WFIRST

Eff. Aperture 1.13m 1.3m 1.1m 2.28m

FOV 0.44 deg2 0.375 deg2 0.585 deg2 0.281 deg2

Wavelengths RIZ/YJH 0.92-2.4 μm 0.92-2.4 μm 0.93-2 μm

FWHM@1μm 0.21” 0.19” 0.23” 0.10”

Pixel Size 0.1”/0.3” 0.18” 0.18” 0.11”

Time 0 (300d) 432d 266d 432d (?)

Lifetime 6 years 5 years 3 years 5+1 years +?

Orbit L2 L2 L2 Geo ?

Hardware Yields.• Yields scale with:

– Yield ~propto total observing time

– Yield ~propto number of stars

– Yield ~propto (photon rate)α , with α~0.3 to 1.• Primary hardware dependencies:

– FOV.– Aperture.– Bandpass (total throughput + red cutoff).– Resolution (background).– Pointing constraints.

• Secondary hardware dependencies:– Data downlink, slew and settle

Microlensing Simulations.(Matthew Penny)

Mercury @ 2.2 AU

(~28 sigma)

Free floating Mars

(~23 sigma)

Predicted Planet Yields.M/MEarth Euclid DRM1 DRM2 AFTA-

WFIRST

0.1 10 30 21 39

1 66 239 176 301

10 197 794 599 995

100 144 630 484 791

1000 88 367 272 460

10,000 41 160 121 201

Total 546 2221 1676 2787

Euclid DRM1 DMR2 WFIRST-2.4

5 33 27 41

Bou

nd

F.F.

Eart

h

All yields by Matthew Penny.

Exoplanet Demographics with WIFRST.

WFIRST will:• Detect 2800 planets, with

orbits from the habitable zone outward, and masses down to a few times the mass of the Moon.

• Have some sensitivity to “outer” habitable zone planets (Mars-like orbits).

• Be sensitive to analogs of all the solar systems planets except Mercury.

• Measure the abundance of free-floating planets in the Galaxy with masses down to the mass of Mars

• Characterize the majority of host systems.

Together, Kepler and WFIRST complete the statistical

census of planetary systems in the Galaxy.

WFIRST/2.4

Search Area

Kepler

Search Area

Exoplanet Demographics with WIFRST.

WFIRST will:• Detect 2800 planets, with

orbits from the habitable zone outward, and masses down to a few times the mass of the Moon.

• Have some sensitivity to “outer” habitable zone planets (Mars-like orbits).

• Be sensitive to analogs of all the solar systems planets except Mercury.

• Measure the abundance of free-floating planets in the Galaxy with masses down to the mass of Mars

• Characterize the majority of host systems.

Together, Kepler and WFIRST complete the statistical

census of planetary systems in the Galaxy.

Synergy with JWST!!

WFIRST+

Coronagraph

Exoplanet Direct ImagingWFIRST-2.4 will:• Characterize the spectra of

roughly a dozen radial velocity planets.

• Provide crucial information on the physics of planetary atmospheres and clues to planet formation.

• Respond to decadal survey to mature coronagraph technologies, leading to first images of a nearby Earth.

Spectra at R=70 easily distinguishes

between a Jupiter-like and Neptune-

like planet at 2 AU about stars of

different metalicity.

Debris Disk ImagingWFIRST/2.4 will:• Measure the amount and

distribution of circumstellar dust,

• Measure the large scale structure of disks, revealing the presence of asteroid belts and gaps due to unseen planets., Measure the size and distribution of dust grains,

• Provide measurements of the zodiacal cloud in other systems.

http://hubblesite.org/newscenter/archive/releases/2004/33/image/c/

Debris disk around the young (~100 Myr), nearby (28 pc) sun-

like (G2 V0) star HD 107146

Guest Investigator Science.

• HST aperture with ~200✕ the FOV.

• Archival science in bulge, SNe and HLS surveys.

• ~25% of time to GO programs.

High Latitude Survey ~2000 sq. degrees in four filters +

slitless grism spectrscopy.

To Do.

• HST imaging of target fields.• Spitzer/Kepler monitoring of

microlensing events.• HST follow-up of planet detections.• H-band ground-based microlensing

survey.• Manpower!

Summary.• The demographics of planets beyond the snow line

provides crucial constraints on planet formation theories and habitability.

• AFTA-WFIRST enables qualitatively new, exciting science: sub-Earth-mass planets, free-floating planets, outer habitable zone planets, mass measurements.

• AFTA-WIFRST will complete the census begun by Kepler, and will revolutionize our understanding of cold planets.

• But, lots to do!

Exoplanet Science with

WFIRST.

WFIRST+C Exoplanet Science

Microlensing Survey High Contrast Imaging

Monitor 200 million Galactic bulge stars every 15 minutes for 1.2 years

2800 cold exoplanets

300 Earth-mass planets

40 Mars-mass or smaller planets

40 free-floating Earth-mass planets

Survey up to 200 nearby stars for planets and debris disks at contrast levels of 10-9

on

angular scales > 0.2”

R=70 spectra and polarization between 400-900 nm

Detailed characterization of up to a dozen giant planets.

Discovery and characterization of several Neptunes

Detection of massive debris disks.

The combination of microlensing and direct imaging will dramatically expand our knowledge of other solar systems and will provide a first glimpse

at the planetary families of our nearest neighbor stars.

Complete the

Exoplanet Census

Discover and Characterize

Nearby Worlds

• How do planetary systems form and evolve?

• What are the constituents and dominant physical processes

in planetary atmospheres?

• What kinds of unexpected systems inhabit the outer regions

of planetary systems?

• What are the masses, compositions, and structure of nearby

circumstellar disks?

• Do small planets in the habitable zone have heavy

hydrogen/helium atmospheres?

Toward the “Pale Blue Dot”

Microlensing Survey High Contrast Imaging

• Inventory the outer parts of planetary systems, potentially the source of the water for

habitable planets.

• Quantify the frequency of solar systems like our own.

• Confirm and improve Kepler’s estimate of the frequency of potentially habitable planets.

• When combined with Kepler, provide statistical constraints on the densities and heavy

atmospheres of potentially habitable planets.

• Provide the first direct images of planets around our nearest neighbors similar to our

own giant planets.

• Provide important insights about the physics of planetary atmospheres through

comparative planetology.

• Assay the population of massive debris disks that will serve as sources of noise and

confusion for a flagship mission.

• Develop crucial technologies for a future mission, and provide practical demonstration

of these technologies in flight.

WIFRST will lay the foundation for a future flagship direct imaging mission capable of detection and

characterization of Earthlike planets.

Science and technology foundation for the New

Worlds Mission.

Courtesy of Jim Kasting.