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1 Exoplanet detection (500+) Gravitational attraction between a stellar mass (sun) and planets (bigger the better, why?) 2 detected exoplanets to scale for planet orbital makes sun’s position wobble about barycenter. radius (planets not to Big question is: How many planets are in lifescale!) 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 (Mercurylike) and the blue zone is to cold and makes gaseous planets (Jupiter-like) Our solar system to scale for Jupiter and Saturn orbital radius 2 Exoplanet detection methods Transit method: light dims Direct observation infrared Radial velocity wobble (Doppler shift) 3 Exoplanet detection via gravity causing sun wobble 4 Kepler mission (launched 2009): watching 100,000 nearby stars. We will know statistical probability of earth-like planets (liquid water) in 4 years 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. 5 3,000 light-year search of stars in Sagittarius Arm 6 Stellar mass (our sun masses) Predicted Exoplanet detectability Planet orbit (earth-sun distance (AU)) Terrestrial inner-orbit planets •50 planets if most have R ~ 1.0 Re •185 planets if most have R ~ 1.3 Re •640 planets if most have R ~ 2.2 Re Giant inner planets based on reflected light •About 870 planets with periods less than one week Kepler’s third law: T2 ~ R3 Giant planets based on transits •135 inner-orbit planets •Densities for 35 of the inner-orbit planets, and 30 outer-orbit planets. 7 8 9 Suns orbits around 4 million solar mass black hole at galactic center of milky way galaxy 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. 10 Galactic core black-hole sun motion for 8 yrs Gravity is a busy force moving stuff around rapidly 11 Supermassive black holes at center of most all galaxies Andromeda central SM blackhole Milky way galaxy center 12 Gravity is the force 13