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Lecture 1: Introduction & Methods

This lecture provides an introduction to the methods and techniques used in the discovery and study of exoplanets, with a focus on the NASA Kepler mission. To date, over 330 exoplanets across 31 systems have been identified, with statistics highlighting the prevalence of gas giants and the emerging category of Super-Earths. The complexities of direct detection, radial velocity techniques, and transit measurements are discussed, showcasing the advancements and ongoing challenges in understanding planets beyond our solar system.

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Lecture 1: Introduction & Methods

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  1. Planetary Systems Orbiting Diverse Stars Lecture 1: Introduction & Methods Introduction Techniques for discovery & study The NASA Kepler mission

  2. 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 …

  3. Small stars, Brown dwarfs, & planets Evolution of luminosity with time for different masses Burrows 2000)

  4. 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

  5. The Planets of our Solar System

  6. New types ofplanets: Hot Jupiters Super-Earths (Sasselov 2008)

  7. Super-Earths “Confusion region” Mass range: ~1 - 10 Earth mass

  8. The super-Earths M-R diagram max radius H2O min radius Fix one ratio: Earth-like Fe/Si Valencia, Sasselov, O’Connell (2007)

  9. Super-Earths: excellent homes for life Image: S.Cundiff (Sasselov 2008)

  10. Techniques for discovery: Star-to-planet inequalities • In light: 1010 (optical) to 107 (infrared) • In mass: 105 to 103 • In size: 102 to 10.

  11. Exoplanet discovery space:2007 & looking forward Planet Mass Planned Kepler space mission:may detect Earth-like planets,but measure only size, not mass

  12. Direct Detection of Planets • Direct detection is challenging because of the technical limits of telescopic observations

  13. Direct Detection of Planets • Three planets orbiting HR8799 …if star’s age is < 300 Myr (Marois et al. 2008)

  14. Direct Detection of Planets • There may be more planets, but more obs needed to confirm even this one. (Kalas et al. 2008)

  15. 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)

  16. HD 209458b: a Hot Jupiter

  17. 1 m/s The HARPS planet-search program ESO 3.6 – La Silla - Geneva Observatory - Physikalisches Institut, Bern - Haute-Provence Observatory - Service d’Aeronomie, Paris - ESO

  18. (from C. Lovis) HD 40307

  19. 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…

  20. Harvard/Smithsonian/MIT astro-comb project Summer 07: Ti:sapphire femtosecond laser comb 2008: develop high-rep ratecomb for astro applicationsand demo on mountain-top 2009: Optimized system for1 cm/s Doppler shift precision Fall 2007: characterize with astro spectrograph Li et al. (2008, Nature, April)

  21. Transits: A Method for Planet Discovery & Study

  22. TransitMeasurements

  23. Transit & eclipse of HD189733b Heather Knutson & Dave Charbonneau (2007)

  24. OGLE-TR-113b Doppler Shift Transit Light Curve Konacki, Torres, Sasselov, Jha (2004)

  25. 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)

  26. 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)

  27. Transits of exoplanets from Hubble: Illustration of high precision: s(RP)~3% TrES-1 HD 209458 Spot Light Flux Time Brown et al. (2006)

  28. Mass-RadiusDiagram: Hot Jupiters Super-Earths (Sasselov 2008)

  29. A New super-Neptune: HAT-P-11b Bakos, Noyes, Pal, Latham, Sasselov et al. (2009)

  30. Transit & eclipse of HD189733b Heather Knutson & Dave Charbonneau (2007)

  31. Spectrum for HD 189733b Obtained by transit transmission & eclipse emission Inverse Residual Flux Wavelength

  32. New 2 m Spectrum for HD 189733b (Swain et al. 2008)

  33. NASA Kepler mission: transit search for planets Cygnus / Lyra (RA=19h23m, Dec=44.5d)

  34. Completing the Copernican Revolution:the discovery of “New Earth” NASA Mission - Mar. 2009

  35. 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

  36. 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!

  37. 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.

  38. 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…

  39. Some Conclusions: • Extrasolar Earths - a worthy (and historic) goal: • help us understand planet formation in general • help us constrain pre-biotic chem / pathways to life • We now have the tools - to discover & study: • Transits (Kepler), spectrograph (astro-comb)

  40. Super-Earths “Confusion region” Mass range: ~1 - 10 Earth mass

  41. Super-Earths as proxies for Earth How to distinguish mini-Neptune from super-Earth: < Three types of atmospheres (Miller-Ricci, Seager, Sasselov 2008)

  42. Super-Earths as proxies for Earth How to distinguish mini-Neptune from super-Earth: (Miller-Ricci, Seager, Sasselov 2008)

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