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2. Exoplanet detection (500+) 2 Gravitational attraction between a stellar mass (sun) and planets (bigger the better, why?) makes sun’s position wobble about barycenter. Big question is: How many planets are in life- zone where liquid water is stable? Life zone is where a sun’s luminosity and a planet’s orbital radius are correct: the green zone below. The red zone is too hot (Mercury- like) and the blue zone is to cold and makes gaseous planets (Jupiter-like) 2 detected exoplanets to scale for planet orbital radius (planets not to scale!) Our solar system to scale for Jupiter and Saturn orbital radius

3. Exoplanet detection methods 3 Transit method: light dims Radial velocity wobble (Doppler shift) Direct observation infrared

4. Exoplanet detection via gravity causing sun wobble 4

5. Kepler mission (launched 2009): watching 100,000 nearby stars. We will know statistical probability of earth-like planets (liquid water) in 4 years 5 The Kepler-scope: measure 100,000 stars brightness (photometry) at same time (wide view field) to find planets The local structure of our Galaxy, the Milky Way. The stars sampled are similar to the immediate solar neighborhood. Young stellar clusters, ionized hydrogen (HII) regions and the neutral hydrogen (HI) distribution define the arms of the Galaxy.

6. 3,000 light-year search of stars in Sagittarius Arm 6

7. Predicted Exoplanet detectability 7 Terrestrial inner-orbit planets 50 planets if most have R ~ 1.0 R e 185 planets if most have R ~ 1.3 R e 640 planets if most have R ~ 2.2 R e Giant inner planets based on reflected light About 870 planets with periods less than one week Planet orbit (earth-sun distance (AU)) Stellar mass (our sun masses) Kepler’s third law: T 2 ~ R 3 Giant planets based on transits 135 inner-orbit planets Densities for 35 of the inner-orbit planets, and 30 outer-orbit planets.

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10. Suns orbits around 4 million solar mass black hole at galactic center of milky way galaxy 10 A black hole has the biggest gravitational pull of any object. The gravity is so strong that the mass-energy of light is frozen in time on the event horizon so that no radiation is emitted. Gravity makes time run slow. At the black hole event horizon time stops and all energy-matter dissapears into the singularity.

11. Galactic core black-hole sun motion for 8 yrs 11 Gravity is a busy force moving stuff around rapidly

12. Supermassive black holes at center of most all galaxies 12 Milky way galaxy center Andromeda central SM blackhole

13. Gravity is the force 13