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EXAOC SCIENCE KICK-OFF MEETNG

This meeting, held on 19th July 2004 at UC Berkeley, focused on the science goals and utility of high contrast imaging in fields such as exoplanet detection, planetary systems, and circumstellar disks.

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EXAOC SCIENCE KICK-OFF MEETNG

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  1. EXAOC SCIENCE KICK-OFF MEETNG James Graham UC Berkeley UCB 19th July 2004

  2. HIGH CONTRAST SCIENCE GOALS • Imaging planets & planetary systems • Improved statistics • Sample beyond the snow line ( a > 3 AU, P > 5 yr) • Probe planetary atmospheres • Protoplanetary disks • Structure & evolution of dust & gas orbiting T Tauri & Herbig Ae/Be stars • Debris disks & zodi dust • Structure in inner disks where planets form & orbit • Disk/planet interactions • Brown dwarfs • Frequency of brown companions (e.g., HR 7672 & LHS 2397) • Mass loss from from evolved stars • Destruction of planetary systems while seeding the Galaxy for the next generation of solar systems

  3. UTILITY OF HIGH CONTRAST IMAGING • Broad scientific application • Exoplanet detection • Circumstellar disks (proto-planetary & debris disks) • Mass transfer & loss in cataclysmic variables, symbiotic stars, & supergiants • Instant gratification • Indirect searches need 10-103 yr for 5-100 AU orbits to complete • Common proper motion companions confirmed in ~ 1 yr • Resolve M sin(i ) ambiguity • Complex & multiple-planet systems established unambiguously • Imaging provides a snap-shot of: • Planets, zodi dust blobs & brown dwarfs or stellar companions • Fourier approach of indirect searches requires many orbits for complex systems ( ~ 1/t) • Sensitivity to planets orbiting non-solar analogs • Doppler is ineffective for early F & A stars • High detection efficiency for young systems • E.g., ~ 50% in a nearby (50 pc) young (10 Myr) association

  4. HOW TO FIND PLANETS:INDIRECT DECTION • Measure the Doppler shift of the light from a star as a function of time • The acceleration of the star reflects the gravitational pull of an unseen planetary companion • The amplitude is small • Jupiter's gravitational pull causes the Sun to wobble with a velocity amplitude of 12 m/s with a period of 11 years

  5. INDIRECT DETECTION

  6. T(Keck)=8.0 yrs T(Career)~30.0 yrs DOPPLER PLANETS

  7. ARCHITECTURE OF PLANETARY SYSTEMS • 110 Doppler exoplanets • 5% of targeted stars possess massive planets • A diversity of exoplanet systems exist… • How do planets form? • Is the solar system typical? • What is the abundance of solar systems? • Doppler surveys raise new questions, e.g., • What produces the dynamical diversity in exoplanet systems? • Direct imaging can answer these questions • Fast alternative to Doppler surveys • Searching greatest stellocentric distances for planets • Characterizing the frequency and orbital geometries of planets > 3 AU will show if our solar system is unique • Reveal the zone where planets may form by gravitational instability • Uncover traces of planetary migration

  8. PLANETARY DIVERSITY

  9. HOW TO FIND PLANETS

  10. HOW TO FIND PLANETS Voyager family portrait

  11. 10 AU Star exo-Jupiter PLANET FORMATION PATHWAYS • Classical core accretion • Grain growth forms planetesimals • Gaseous envelope accreted • Terrestrial & giant planets (metal-rich) • Giant planets form at ~ 5 AU, in 1-10 Myr • Orbital migration & dynamical interactions alter orbital radii & eccentricites

  12. Qmin=1.7 Mayer et al. 2002 160 yr 350 yr 20 AU Qmin=1.4 PLANET FORMATION PATHWAYS • Disk instability • Giant planets form over a range of radii & masses • Giant exoplanets? • Uranus & Neptune? • Form planets is short lived disks • < 1000 yrs • Giant planets differ from Solar System • High eccentricity, stellar composition • May not favor terrestrial planets • Disk disrupted in < 1 Myr • Core accretion and gravitational instability both explain the properties of extrasolar planets, but make different predictions for terrestrial planets • Which pathway is dominant?

  13. DOPPLER SEARCHES ARE BIASED • Doppler & direct imaging are complementary • Doppler biased to short periods (90% have a < 3.5 AU) • Primitive theory until we probe the planet formation zone • Bottom up classical core accretion: dust, planetesimals, then planets • Planets form where raw materials are abundant • Top down; gravitational disk instabilties • Planets form where unstable modes grow rapidly • Semi-major axis distribution traces initial distribution modified by • Orbital migration & dynamical relaxation • Planet-planet, disk-planet & planetisemal-planet interactions • Probe planets at a > 3 AU - 100 AU • dN / d log(a) is flat or more likely increasing as ~ a1/2 • > 1/2-3/4 of all planets may be in the EXAOC search space • Planetary evolution in action for young systems (10 - 100 Myr) • Detect some objects in common with Doppler

  14. YOUNG EXTRASOLAR PLANETS 1 Million years 10 Million years 100 Million years 4.5 Billion years Adapted from D. Kirkpatrick & R. Hurt

  15. EXOPLANET EVOLUTION Burrows et al. 2003 Mass (MJ) Age (Gyr)

  16. PLANET PHASE SPACE Burrows et al. 2003 log10 (g) (cm s-2) Teff (K)

  17. PLANET SPECTRA Burrows et al. 2003

  18. DEBRIS DISKS • Zodi & Kuiper-belt dust in the Solar System is removed by Poynting-Robertson drag in < 100 Myr • Short-lived material after the dispersal of the protoplanetary disk implies dust production • Collisions of planetesimals • Sublimation of sun-grazing comets • Planetary perturbations are a known source of excitation of eccentricity • Debris disks are indirect evidence for planets • 15% of A stars have 10-100 zodis at Kuiper Belt radii (10-100 AU) • Only Vega, Fomalhaut, e Eri, b Pic, HR 4796 & HD 141659 have been resolved • Only 1000-10,000 zodis have been imaged

  19. Key Topics • WFS limiting magnitude

  20. Key Topics • Inner working distance

  21. Key Topics • WFS limiting mag (3, 5, 7 & 9) vs. supaperture size (12, 18 & 25 cm)

  22. Key Topics • Long wavelength performance • New SNR calculator correctly includes • Planet photon noise • Detector noise • AO thermal background photon noise • Telescope background photon noise • Sky background photon noise • Halo photon shot • Speckle noise • Necessary for  > 2.4 µm • Redo the proposal example • 5.8 % planet detection rate vs. 6.5% • L-prime example • 13 cm subaperture, 12 nm WFE • Find 59 planets (2.6%)

  23. Key Topics • Optimizing AO loop parameters & speckle supression • 18 cm subaperture • I = 7 mag • AO loop rate of 500, 1000, 1500 & 2000 Hz • Speckle noise suppression of x1, x4 & x16

  24. Fin

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