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Lecture 16: Exoplanets, Brown Dwarfs,

Lecture 16: Exoplanets, Brown Dwarfs,. Full Moon by Michael Light negatives by astronauts. This class Exoplanets Chapt 15 brown dwarfs Read before coming to class The Sun Chapt 16 Stars Chapt 17 flux, luminosity, magnitudes, spectra Hertzsprung-Russell Diagram. News! Oct 19 th.

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Lecture 16: Exoplanets, Brown Dwarfs,

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  1. Lecture 16: Exoplanets, Brown Dwarfs, • Full Moon by Michael Light • negatives by astronauts. • This class • Exoplanets Chapt 15 • brown dwarfs • Read before coming to class • The Sun Chapt 16 • Stars Chapt 17 • flux, luminosity, magnitudes, spectra • Hertzsprung-Russell Diagram

  2. News! Oct 19th • Comet Siding Spring, will pass within ~139,500 kilometers of the Red Planet • dist < 1/2 dist between Earth & Luna • dist < 1/10 dist of any known comet flyby of Earth. Named after Siding Spring Observatory

  3. Exoplanets and their planetary systems: David Lafreniere, Ray Jayawardhana, Marten H. van Kerkwijk (University of Toronto, Gemini Observatory) This image could be the first direct image of a planet (upper left) around another Sun-like star (center). • Extra-solar planets == exoplanets • How different from those in our SS (Solar System)? • Are our theories about SS formation applicable to other systems?

  4. Atacama Larger Millimeter/submillimeter Array (ALMA) • 5000 m • 64 antennas • 22 countries (incl. Canada) • molecular emission lines •  Molecular gas distribution, T, density & motions.

  5. Proplyd disk around HD 21997 DUST RING (Hershel Space Obs. & ALMA) CO gas (ALMA) Gas rotating around host star (ALMA) • ~10 million years old • “hybrid disk”  both planetesimals (dust) and gas • dust more extended

  6. Exoplanets: Characteristics MASSES # of planets Mass Uranus Super-Earths Mass Earth Mass Uranus • Roughly 1822 planets detected (this week). • Interactive catalogue at http://exoplanet.eu/ • masses in Jupiter’s mass (Mjup: 318 x Mearth). • maximum mass ~ 50 x Mjup •  gas giants

  7. Exoplanets: Characteristics DISTANCES # of planets • Roughly 1822 planets detected. • Interactive catalogue at http://exoplanet.eu/ Distance Earth Distance Neptune • distance from host star in AU • maximum distance a few thousand AU •  most are closer than Earth

  8. Exoplanets: Characteristics • small mass planets rare? or • was our observational method biased?

  9. Exoplanets: Radial Velocity Method • Radial Velocity == velocity along our line of sight. • Fgrav between star + planet causes star to be pulled towards planet. •  star wobbles  Star’s motion is Doppler Shifted. • shift correlates with Fgrav Movie

  10. Exoplanets: Radial Velocity Method • If m (==planet mass) large, then F large  radial velocity large. • If r (== star – planet distance) small, then F large  radial velocity large.  Easier to detect massive planet close to star.

  11. Review Most exoplanets detected to ~2013 had masses similar to Jovians & orbit closer to their star than Jupiter does to ours.

  12. Exoplanets: Doppler Shift Method • Period Jupiter (5 AU) = 12 yrs. • long time for one person to observe one star! note Saturn’s Period vs career length.  Easier to detect planets close to star. • Currently team work  longer time.

  13. Artist’s impression: The star Gliese 667 C, which belongs to a triple system – 2 of the stars seen in the background. The 6 Earth-mass exoplanet circulates around its low-mass host star at a distance equal to only 1/20th of the Earth-Sun distance. Exoplanets • Planet around alpha Centauri B! Sun-like star. • 4.3 ly distant, 3 stars. • Earth mass planet • P~3 days closer than Mercury • High Accuracy Radial Velocity Planet Searcher (HARPS) spectrograph, on ESO's 3.6-metre telescope, discovery of 150 exoplanets Sept 12/11. • at that time HARPS helped discover most of the planets of mass < 20 Earth masses -> super-Earths and small gas giants. (About 40). • most low-mass candidates in multi-planet systems.

  14. Exoplanets -- Kepler 78b • r = 1.2 x Earth & M = 1.7 x Earth  density ~ Earth => same density • orbit’s every 8.5 hrs => 2000K hotter • tidal forces will break it apart HARPS & HIRES spectrograph on Keck I

  15. Exoplanets • CoRoT- 7b (HARPS on ESO 3.6m) • 5 earth-masses • Density Earth-like  rocky. • 23 * closer to star than Mercury to Sun • Gliese 581g ((aka Zaramina’s World) (HIRES on Keck) • red dwarf star • in habitable zone (.15 AU) – distance for liquid H2O • 3* earth-mass; 1.5* earth-diameter

  16. Exoplanets: Transit Method movie • method for Canada's space telescope called MOST • Produces a light curve (Intensity vs Time) as the planet orbits. • larger planets  larger dips in light curve. • closer planets  shorter time between dips (e.g. within career).  Easier to detect large planets close to their star. There are earth-sized planets but harder to detect.

  17. Exoplanets • NASA’s Kepler Mission • Launched March 2009 - now finished. • This is a test on a known planet.

  18. Exoplanets -- Kepler 78b How do we get planet radius for density? Transit method. • r = 1.2 x Earth & M = 1.7 x Earth  density ~ Earth => same density

  19. Combine Spectroscopy and Transit method  Temperature Maps • Tidally locked Hot Jupiter WASP-43b • too distant to be photographed • T and H2O abundance at different longitudes

  20. Exoplanets: Imaging Technique low resolution high resolution Recall resolution.

  21. Resolved and Unresolved: • Resolved galaxies in background. • Generally structure of stars cannot be distinguished unresolved.

  22. Exoplanets: Imaging Technique David Lafreniere, Ray Jayawardhana, Marten H. van Kerkwijk (University of Toronto, Gemini Observatory) This image could be the first direct image of a planet (upper left) around another Sun-like star (center). • Resolve the planet from its host star. • Do not resolve surface of either star or planet.

  23. Imaging Technique  birth of a giant planet! • ESO’s Very Large Telescope on right with adaptive optics and coronograph. HST: protoplanetary disk ESO: protoplanet candidate

  24. Exoplanets: Imaging Technique • Found 51 planets, all but 2 have M >= 3*Mjup, up to 32*Mjup • Fomalhaut planet < 3 Earth masses.

  25. Review There was an observational bias systems with Hot Jupiters • mass  stronger Doppler Shift in radial velocity method  larger light dip in transit method • proximity  shorter time in radial velocity method shorter time in transit method • but there are super-Earths.

  26. Summary • There are planets smaller than Jupiter • Harder to detect them. • Now have 405 planetary systems with planets M<10*M_Earth. (333 multiple planet systems) • 885 planets • Other planetary systems are different than ours • massive planets close to star

  27. Exoplanets: planets close to host stars • Migration while there is still the gas disk: • E.g. friction between the gas disk and the protoplanets cause the protoplanets to lose energy and spiral inwards. • Gap blown by proto-star’s wind. • Particularly effective for “Hot Jupiters”.

  28. Later Migration:The Nice Model • In the era of planetesimal ejection • Neptune moves outside orbit of Uranus.

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