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The Detection and Properties of Planetary Systems Prof. Dr. Artie Hatzes Artie Hatzes Tel:036427-863-51 Email: [email protected] www.tls-tautenburg.de→Lehre→Vorlesungen→Jena The Detection and Properties of Planetary Systems: Wed. 14-16 h Hörsaal 2, Physik, Helmholz 5 Prof. Dr. Artie Hatzes The Formation and Evolution of Planetary Systems: Thurs. 14-16 h Hörsaal 2, Physik, Helmholz 5 Prof. Dr. Alexander Krivov Exercises Wed. 12-14 and Thurs. 16-18 h Seminarraum AIU, Schillergässchen 2 Dr. Torsten Löhne Detection and Properties of Planetary Systems 06. April Introduction and Background 13. AprilThe Doppler Method: Techniques 20. AprilThe Doppler Method: Results 27. April Astrometry 04. May Microlensing 11. May The Transit Method: PhotometricTechniques 18. May The Transit Method: Results from the Ground 25. May The Transit Method: Results from CoRoT and Kepler 01. June Exoplanetary Atmospheres 08. June (Exoplanet Host Stars) 15. June No Class (CoRoT Symposium) 22. June Direct Imaging of Exoplanets 29. June Planets off the Main Sequence 06. July Planets in Different Environments Preliminary Program, subject to change Literature Planet Quest, Ken Croswell (popular) Extrasolar Planets, Stuart Clark (popular) Extasolar Planets, eds. P. Cassen. T. Guillot, A. Quirrenbach (advanced) Planetary Systems: Formation, Evolution, and Detection, F. Burke, J. Rahe, and E. Roettger (eds) (1992: Pre-51 Peg) Transiting Exoplanets, Carole Haswell Resources The Extrasolar Planet Encyclopaedia (Jean Schneider): www.exoplanet.eu (note www.exoplanets.eu sends you to the Geneva Planet Search Program) • In 7 languages • Tutorials • Interactive catalog (radial velocity, transits, etc) • On line histrograms and correlation plots • Download data Resources: The Nebraska Astronomy Applet Project (NAAP) http://astro.unl.edu/naap/ This is the coolest astronomical website for learning basic astronomy that you will find. In it you can find: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. Solar System Models Basic Coordinates and Seasons The Rotating Sky Motions of the Sun Planetary Orbit Simulator Lunar Phase Simulator Blackbody Curves & UBV Filters Hydrogen Energy Levels Hertzsprung-Russel Diagram Eclipsing Binary Stars Atmospheric Retention Extrasolar Planets Variable Star Photometry Resources The Nebraska Astronomy Applet: An Online Laboratory for Astronomy http://astro.unl.edu/naap/ http://astro.unl.edu/animationsLinks.html Pertinent to Exoplanets: 1. Influence of Planets on the Sun 2. Radial Velocity Graph 3. Transit Simulator 4. Extrasolar Planet Radial Velocity Simulator 5. Doppler Shift Simulator 6. Pulsar Period simulator 7. Hammer thrower comparison And where is Nebraska? For iPhone users there is a free exoplanet app Exoplanets is a fast moving field, the best literature is the journals NASA Astronomical Data Systems Abstract Service: http://adswww.harvard.edu/ads_abstracts.html „Astronomy and Astrophysics Search“ Astro-ph preprint service: http://arxiv.org/ Our Solar System Today A quick tour of our solar system A good source for this is: www.nineplanets.org and solarsystem.nasa.gov Mercury Distance: 0.38 AU Period: 0.23 years Radius: 0.38 RE Mass: 0.055 ME Density 5.43 gm/cm3 (second densest) Satellites: None Structure: Iron Core (~1900 km), silicate mantle (~500 km) Temperature: 90K – 700 K Magnetic Field: 1% Earth Atmosphere: Thin, bombarded by Solar Wind and constantly replenished Venus Distance: 0.72 AU Period: 0.61 years Radius: 0.94 RE Mass: 0.82 ME Density 5.4 gm/cm3 Satellites: None (1672 Cassini reported a companion) Structure: Similar to Earth Iron Core (~3000 km), rocky mantle Temperature: 400 – 700 K (Greenhouse effect) Magnetic Field: None (due to slow rotation) Atmosphere: Mostly Carbon Dioxide Pancake volcanoes Magellan Radar Imaging Sif Mons Earth Distance: 1.0 AU (1.5 ×1013 cm) Period: 1 year Radius: 1 RE (6378 km) Mass: 1 ME (5.97 ×1027 gm) Density 5.50 gm/cm3 (densest) Satellites: Moon (Sodium atmosphere) Structure: Iron/Nickel Core (~5000 km), rocky mantle Temperature: -85 to 58 C (mild Greenhouse effect) Magnetic Field: Modest Atmosphere: 77% Nitrogen, 21 % Oxygen , CO2, water Earth Moon System from Surveyor and Mars Express: The Double Planet Mars Distance: 1.5 AU Period: 1.87 years Radius: 0.53 RE Mass: 0.11 ME Density: 4.0 gm/cm3 Satellites: Phobos and Deimos Structure: Dense Core (~1700 km), rocky mantle, thin crust Temperature: -87 to -5 C Magnetic Field: Weak and variable (some parts strong) Atmosphere: 95% CO2, 3% Nitrogen, argon, traces of oxygen Phobos Deimos Are believed To be captured asteroids Jupiter Distance: 5.2 AU Period: 11.9 years Diameter: 11.2 RE (equatorial) Mass: 318 ME Density 1.24 gm/cm3 Satellites: > 20 Structure: Rocky Core of 10-13 ME, surrounded by liquid metallic hydrogen Temperature: -148 C Magnetic Field: Huge Atmosphere: 90% Hydrogen, 10% Helium The Oscillating Brown Oval (Hatzes et al. 1981) Aurorae on Jupiter Saturn Distance: 9.54 AU Period: 29.47 years Radius: 9.45 RE (equatorial) = 0.84 RJ Mass: 95 ME (0.3 MJ) Density 0.62 gm/cm3 (least dense) Satellites: > 20 Structure: Similar to Jupiter Temperature: -178 C Magnetic Field: Large Atmosphere: 75% Hydrogen, 25% Helium Uranus Distance: 19.2 AU Period: 84 years Radius: 4.0 RE (equatorial) = 0.36 RJ Mass: 14.5 ME (0.05 MJ) Density: 1.25 gm/cm3 Satellites: > 20 Structure: Rocky Core, Similar to Jupiter but without metallic hydrogen Temperature: -216 C Magnetic Field: Large and decentered Atmosphere: 85% Hydrogen, 13% Helium, 2% Methane HST Image Voyager Neptune Distance: 30.06 AU Period: 164 years Radius: 3.88 RE (equatorial) = 0.35 RJ Mass: 17 ME (0.05 MJ) Density: 1.6 gm/cm3 (second densest of giant planets) Satellites: 7 Structure: Rocky Core, no metallic Hydrogen (like Uranus) Temperature: -214 C Magnetic Field: Large Atmosphere: Hydrogen and Helium 2006 IAU Definition of a Planet 1. is in orbit around the Sun, 2. has sufficient mass to assume hydrostatic equlibrium (a nearly round shape), and 3. has „cleared the neighborhood" around its orbit. If a non-satellite body fulfills the first two criteria it is termed a „dwarf planet“. Originally, the IAU wanted to consider all dwarf planets as planets. Under the new definition Pluto is no longer a planet, but rather a dwarf planet. 9 Pluto before 2006 Pluto at the IAU 2006 Pluto today Completing the Census: Satellites 8 Europa Titan Io Triton Planetary Rings Jupiter Saturn Uranus Neptune Trans-Neptunian Objects 5 7 Plutoids Name Orcus Ixion Huya Varuna Quaoar Sedna Pluto Radius (km) 1100 980 480 780 1290 1800 2274 Distance (AU) 39 40 40 43 44 486 39.5 Comets Debris Disks Extrasolar Planets Why Search for Extrasolar Planets? • How do planetary systems form? • Is this a common or an infrequent event? • How unique are the properties of our own solar system? • Are these qualities important for life to form? Up until now we have had only one laboratory to test planet formation theories. We need more! The Concept of Extrasolar Planets Democritus (460-370 B.C.): "There are innumerable worlds which differ in size. In some worlds there is no sun and moon, in others they are larger than in our world, and in others more numerous. They are destroyed by colliding with each other. There are some worlds without any living creatures, plants, or moisture." Giordano Bruno (1548-1600) Believed that the Universe was infinite and that other worlds exists. He was burned at the stake for his beliefs. What kinds of explanetary systems do we expect to find? The standard model of the formation of the sun is that it collapses under gravity from a proto-cloud Because of rotation it collapses into a disk. Jets and other mechanisms provide a means to remove angular momentum The net result is you have a protoplanetary disk out of which planets form. Expectations of Exoplanetary Systems from our Solar System • Solar proto-planetary disk was viscous. Any eccentric orbits would rapidly be damped out – Exoplanets should be in circular orbits • Giant planets need a lot of solid core to build up sufficient mass to accrete an envelope. This core should form beyond a so-called ice line at 3-5 AU – Giant Planets should be found at distances > 3 AU • Our solar system is dominated by Jupiter – Exoplanetary systems should have one Jovian planet • Only Terrestrial planets are found in inner regions • Expect that satellites and rings to be common So how do we define an extrasolar Planet? There is no official IAU definition of an exoplanet. We can simply use mass: Star: Has sufficient mass to fuse hydrogen to helium. M > 80 MJupiter Brown Dwarf: Insufficient mass to ignite hydrogen, but can undergo a period of Deuterium burning. 13 MJupiter < M < 80 MJupiter Planet: Formation mechanism unknown, but insufficient mass to ignite hydrogen or deuterium. M < 13 MJupiter IAU Working Definition of Exoplanet 1. Objects with true masses below the limiting mass for thermonuclear fusion of deuterium (currently calculated to be 13 Jupiter masses for objects of solar metallicity) that orbit stars or stellar remnants are "planets" (no matter how they formed). The minimum mass/size required for an extrasolar object to be considered a planet should be the same as that used in our Solar System. 2. Substellar objects with true masses above the limiting mass for thermonuclear fusion of deuterium are "brown dwarfs", no matter how they formed nor where they are located. 3. Free-floating objects in young star clusters with masses below the limiting mass for thermonuclear fusion of deuterium are not "planets", but are "sub-brown dwarfs" (or whatever name is most appropriate). In other words „A non-fusor in orbit around a fusor“ How to search for Exoplanets Indirect Techniques 1. Radial Velocity 2. Astrometry 3. Transits 4. Microlensing Direct Techniques 4. Spectroscopy/Photometry: Reflected or Radiated light 5. Imaging Radial velocity measurements using the Doppler Wobble The closer the planet, the higher the velocity amplitude: sensitive for near in planets Radial Velocity measurements Requirements: • Accuracy of better than 10 m/s • Stability for at least 10 Years Jupiter: 12 m/s, 11 years Saturn: 3 m/s, 30 years Vobs = 28.4 mp sin i P1/3ms2/3 Astrometric Measurements of Spatial Wobble Center of mass θ= m M a D 2θ 2θ = 8 mas at α Cen 2θ = 1 mas at 10 pcs Current limits: 1-2 mas (ground) 0.1 mas (HST) • Since Δ ~ 1/D can only look at nearby stars Jupiter only 1 milliarc-seconds for a Star at 10 parsecs Microlensing Direct Imaging: This is hard! 1.000.000.000 times fainter planet 4 Arcseconds Separation = width of your hair at arms length The direct imaging of exoplanets is like detecting a firefly next to a lighthouse… For large orbital radii it is easier Transit Searches: Techniques Timing Variations If you have a stable clock on the star (e.g. pulsations, pulsar) as the star moves around the barycenter the time of „maximum“ as observed from the earth will vary due to the light travel time from the changing distance to the earth The Pulsar Planets were discovered in this way Filling the parameter space requires ALL search techniques 2.0 Brown Dwarf Interferometry C5,C6,C8 A5 A0 Log MJupiter -1.0 Imaging RV 1.0 0.0 A0 F3 A5 Jupiter Differential Imaging M5 K5 Transits Saturn M7 Astrometry G0 M9 M0 M8 Uranus M6 G2 Darwin M5 COROT/Kepler -2 Microlensing Earth -2.0 M7 -1.5 -1.0 -0.5 0.0 M9 0.5 Astrometry w/ interferometry 1.0 Log Semi-major axis (AU) 1.5 2.0 The Path of Discovery Space Another reason to search for exoplanets The Earth as viewed from Voyager To find another „blue dot“ „Radial velocity Planets“ „Transit Planets“ „Microlensing Planets“ „Direct Imaging Planets“ ´The first time I taught this class there were • less than 100 planets • 1 transiting planet • No direct images of planets • No microlensing planets • No planet detected by astrometry • No atmospheres detected