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Planetary Systems Orbiting Diverse Stars Lecture 1: Introduction & Methods 1. Introduction 2. Techniques for discovery & study 3. The NASA Kepler mission Where do we stand today? Planets Known to Orbit Other Stars: • Total: 330+ ( 31 systems) discovered to-date • Statistics: • Gas giant planets, like Jupiter & Saturn, exist around >12% of stars (Marcy et al.); • Lower-mass planets (Super-Earths, ~12 known to-date) are more common (Mayor et al.); • No Earth-like planets yet … Small stars, Brown dwarfs, & planets Burrows 2000) Evolution of luminosity with time for different masses Properties of planets & small stars Models: Baraffe et al. four different ages: 0.5, 1, 3, & 5 Gyr Red: Pont et al. (2005) OGLE-TR-122 The Planets of our Solar System New types of planets: Hot Jupiters Super-Earths (Sasselov 2008) Super-Earths “Confusion region” Mass range: ~1 - 10 Earth mass The super-Earths M-R diagram H2O Fix one ratio: Earth-like Fe/Si Valencia, Sasselov, O’Connell (2007) (Sasselov 2008) Image: S.Cundiff Super-Earths: excellent homes for life Techniques for discovery: Star-to-planet inequalities • In light: 1010 (optical) to 107 (infrared) • In mass: 105 to 103 • In size: 102 to 10. Exoplanet discovery space: 2007 & looking forward QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Planned Kepler space mission: may detect Earth-like planets, but measure only size, not mass Direct Detection of Planets • Direct detection is challenging because of the technical limits of telescopic observations Direct Detection of Planets • Three planets orbiting HR8799 …if star’s age is < 300 Myr (Marois et al. 2008) Direct Detection of Planets • There may be more planets, but more obs needed to confirm even this one. (Kalas et al. 2008) Radial Velocities (Doppler method): Discovery & Mass measurement Radial velocities seen in star HD 209458 the variation is due to a planet that is less massive than Jupiter. (Mazeh et al. 1999; Marcy et al. 2000) HD 209458b: a Hot Jupiter The HARPS planet-search program - Geneva Observatory ESO 3.6 – La Silla - Physikalisches Institut, Bern Haute-Provence Observatory Service d’Aeronomie, Paris ESO 1 m/s (from C. Lovis) HD 40307 HARPS-N Spectrometer on WHT HARPS-NEF: Harvard Origins Initiative with Obs. Geneve on the William Herschel telescope (WHT), Canary Islands A HARPS clone, but for several improvements… QuickTime™ and a decompressor are needed to see this picture. Harvard/Smithsonian/MIT astro-comb project Summer 07: Ti:sapphire femtosecond laser comb QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 2008: develop high-rep rate comb for astro applications and demo on mountain-top Fall 2007: characterize with astro spectrograph QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Li et al. (2008, Nature, April) 2009: Optimized system for 1 cm/s Doppler shift precision Transits: A Method for Planet Discovery & Study Transit Measurements QuickTime™ and a YUV420 codec decompressor are needed to see this picture. Transit & eclipse of HD189733b Heather Knutson & Dave Charbonneau (2007) OGLE-TR-113b Doppler Shift Transit Light Curve Konacki, Torres, Sasselov, Jha (2004) The HAT Network: FLWO Mt.Hopkins Arizona … and Hawaii Mauna Kea We have discovered >11 new planets with it in 2 years. (Bakos et al. 2009) What can we learn from transiting extrasolar planets HD 209458b: Dimming of light due to transit, observed with HST. Tells us DIRECTLY: Planet radius, INDIRECTLY: Planet density Planet composition Brown, Charbonneau, Gilliland, Noyes, Burrows (2001) Transits of exoplanets from Hubble: Illustration of high precision: s(RP)~3% Light Flux TrES-1 Spot HD 209458 Time Brown et al. (2006) Mass-Radius Diagram: Hot Jupiters Super-Earths (Sasselov 2008) Bakos, Noyes, Pal, Latham, Sasselov et al. (2009) A New super-Neptune: HAT-P-11b Transit & eclipse of HD189733b Heather Knutson & Dave Charbonneau (2007) Spectrum for HD 189733b Inverse Residual Flux Obtained by transit transmission & eclipse emission Wavelength (Swain et al. 2008) New 2 m Spectrum for HD 189733b NASA Kepler mission: transit search for planets Cygnus / Lyra (RA=19h23m, Dec=44.5d) Completing the Copernican Revolution: the discovery of “New Earth” NASA Mission - Mar. 2009 Kepler is ready to launch: Mar. 5, 2009 Kepler expected yields: ~ 500 super-Earths, ~ 50 Earth analogs; (5-10% good radii) Assembly at Ball Aerospace The “PROBLEM” with KEPLER: not able to get data on masses for small planets - reflex amplitudes will be less than 30 cm /sec. SOLUTION: build a novel Doppler instrument to fit on a large telescope. Use it to measure masses, and hence mean densities for KEPLER’s best candidate Earths & super-Earths! HARPS-N Spectrometer Synergy with Kepler: Provide ability to reach RV amplitudes of about 10 cm /sec. Given Porb and phase from transit, this can translate to 10% masses in the Super-Earth and Earths regime. HARPS-N by Harvard - Geneva on the William Herschel telescope (WHT), Canary Isl. HARPS-N Spectrometer on WHT HARPS-NEF: Harvard Origins Initiative with Obs. Geneve on the William Herschel telescope (WHT), Canary Islands A HARPS clone, but for several improvements… QuickTime™ and a decompressor are needed to see this picture. Some Conclusions: 1. Extrasolar Earths - a worthy (and historic) goal: • help us understand planet formation in general • help us constrain pre-biotic chem / pathways to life 2. We now have the tools - to discover & study: • Transits (Kepler), spectrograph (astro-comb) Super-Earths “Confusion region” Mass range: ~1 - 10 Earth mass Super-Earths as proxies for Earth How to distinguish mini-Neptune from super-Earth: < Three types of atmospheres (Miller-Ricci, Seager, Sasselov 2008) Super-Earths as proxies for Earth (Miller-Ricci, Seager, Sasselov 2008) How to distinguish mini-Neptune from super-Earth: