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Lecture 11: The Discovery of the World of Exoplanets

Lecture 11: The Discovery of the World of Exoplanets. What are exoplanets & where are they? Indirect methods for planet detection. Planets Orbiting Other Stars. Number of planets discovered around other stars: 540 planets 58 multiple planet systems.

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Lecture 11: The Discovery of the World of Exoplanets

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  1. Lecture 11: The Discovery of the World of Exoplanets • What are exoplanets & where are they? • Indirect methods for planet detection

  2. Planets Orbiting Other Stars Number of planets discovered around other stars: 540 planets 58 multiple planet systems

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

  4. Four main methods of discovery: • Direct • Radial velocity or Doppler ‘wobble’ • Transits • Gravitational microlensing

  5. 51 Peg b & HD 209458b: “Hot Jupiters”

  6. Method of discovery: Radial velocity ‘wobble’ of the star 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)

  7. Ups And System vs. Solar System

  8. Kepler-11 System vs. Solar System

  9. HD 209458b: a Hot Jupiter

  10. Transits: A Method for Planet Discovery

  11. Venus in Front of the Sun

  12. TransitMeasurements

  13. Kepler discoveries

  14. Evidence for Planet OGLE-TR-56b Doppler Shift Light Dimming Konacki, Torres, Sasselov, Jha, 2003, Nature

  15. Method of discovery: Radial velocity ‘wobble’ of the star 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. Mass: • For HD 209458b: Mp sin(i) = Ms vs P / 2 ap = const. x (Ms/1.1MSun) Mjup + 0.018 + 0.1 • Transit light curve helps derive the orbit inclination: i = 86o.7 + 0.2 • Both Mp and Rp determined to better than 5%!

  17. 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)

  18. Kepler:New Planets on the Mass-Radius Diagram Radius Mass after Latham et al.’10

  19. Transiting Planets - the search is on! • Transits occur due to chance alignments, therefore one has to observe millions of stars in order to ‘catch’ a few transiting planets; Here at Harvard we have 2 automated networks of small telescopes searching: HAT & MEarth.

  20. The HAT Network: FLWO Mt.Hopkins AZ (Bakos et al. 2004)

  21. … and at Mauna Kea Obs., Hawaii

  22. Main points to take home: • Four main methods of discovery: direct, Doppler wobble, transits, microlensing. • Doppler effect: deriving planet mass. • Transits: (1) detection probability; (2) deriving the radius. • NASA Kepler Mission

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