Exoplanet Science with WFIRST-AFTA Microlensing 18 Scott Gaudi Matthew Penny The Ohio State University 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. Ground Space – Low-magnification events. – Isolate light from the lens star. • Visibility. – Complete coverage. • Smaller systematics. – Better characterization. – Robust quantification of sensitivities. 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. – – • Decadal Survey White Papers: – – • – – 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. – – – • 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). – • Submitted to Midex in 2001, Discovery in 2000, 2004, 2006 Not selected. 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 AFTAWFIRST Wide-Field Instrument • Imaging & spectroscopy over 1000's sq deg. • Monitoring of SN and microlensing fields Eff. Aperture 2.28m FOV 0.281 deg2 Wavelengths 0.7-2 μm • 4 filter imaging, grism + IFU spectroscopy [email protected] 0.10” Coronagraph (descopeable) Pixel Size 0.11” • Imaging of debris disks • 0.7 – 2.0 micron bandpass • 0.28 sq deg FoV (100X JWST FoV) • 18 H4RG detectors (288 Mpixels) • Imaging of ice & gas giant exoplanets • 400 – 1000 nm bandpass Lifetime 5 years +? • 10-9 contrast • 200 milli-arcsec inner working angle Orbit Geo (?) Comparing Designs. Euclid (Opt/NIR) WFIRST DRM1 WFIRST DRM2 AFTAWFIRST 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 [email protected] 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) Bound F.F. Earth Predicted Planet Yields. M/MEarth Euclid DRM1 DRM2 AFTAWFIRST 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 All yields by Matthew Penny. Exoplanet Demographics with WIFRST. Together, Kepler and WFIRST complete the statistical census of planetary systems in the Galaxy. 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. WFIRST/2.4 Search Area Kepler Search Area Exoplanet Demographics with WIFRST. Together, Kepler and WFIRST complete the statistical census of planetary systems in the Galaxy. 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. Synergy with JWST!! WFIRST + Coronagraph Exoplanet Direct Imaging WFIRST-2.4 will: Spectra at R=70 easily distinguishes between a Jupiterlike and Neptune-like planet at 2 AU about stars of different metalicity. • 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. Debris Disk Imaging WFIRST/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. Debris disk around the young (~100 Myr), nearby (28 pc) sun-like (G2 V0) star HD 107146 http://hubblesite.org/newscenter/archive/releases/2004/33/image/c/ Guest Investigator Science. 23.0 23.5 24.0 24.5 25.0 25.5 26.0 26.5 27.0 27.5 28.0 0.8 i 39 VIS r 13 39 0.6 z 39 1.0 1.2 1.6 F106 F129 F158 12 12 14 y 39 LSST (10 yr, S Hemisphere, AM 1.2) WFIRST (1.6k deg 2/yr, ref zodi) Euclid (15-20k deg 2, b=45o) J H Y 31 30 30 Sensitivities of LSST, WFIRST, and Euclid g 39 Labels indicate PSF half light radius in units of 0.01 arcsec u 39 0.4 l (mm) F184 14 2.0 High Latitude Survey ~2000 sq. degrees in four filters + slitless grism spectrscopy. • HST aperture with ~200✕ the FOV. • Archival science in bulge, SNe and HLS surveys. • ~25% of time to GO programs. mag) (AB threshold src 5s pt 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 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. Microlensing Survey High Contrast Imaging Monitor 200 million Galactic bulge stars every 15 minutes for 1.2 years 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 2800 cold exoplanets 300 Earth-mass planets 40 Mars-mass or smaller planets 40 free-floating Earth-mass planets Complete the Exoplanet Census Detailed characterization of up to a dozen giant planets. Discovery and characterization of several Neptunes Detection of massive debris disks. • 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 Discover and Characterize Nearby Worlds Toward the “Pale Blue Dot” WIFRST will lay the foundation for a future flagship direct imaging mission capable of detection and characterization of Earthlike planets. Microlensing Survey • 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. High Contrast Imaging • 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. Science and technology foundation for the New Worlds Mission. Courtesy of Jim Kasting.