Published on November 15, 2007
WE NEED A DIFFERENT APPROACH: 1 WE NEED A DIFFERENT APPROACH Radial velocity (Doppler spectroscopy) method unable to detect Earth-size planets Earth-like planets are about 300 times less massive and about 100 times smaller in area than Jupiter Need a different approach that can detect smaller planets No method exists for detecting habitable planets from ground-based observatories The Kepler Mission uses photometry to detect transits and can detect Earth-size planets from space The Kepler Mission is optimized to detect habitable planets in the habitable zone of solar-like stars USING PHOTOMETRY TO DETECT PLANETS: 2 USING PHOTOMETRY TO DETECT PLANETS Transits Planet crosses line of sight between observer and star and blocks a small amount of light from the star Different from occultation or eclipse Occult means to cover over or to hide Photometry Method of measuring the amount of light A light meter on a camera is a simple photometer USING PHOTOMETRY TO DETECT EARTH-SIZE PLANETS: 3 USING PHOTOMETRY TO DETECT EARTH-SIZE PLANETS The relative change in brightness (DL/L) is equal to the relative areas (Aplanet/Astar) To measure 0.01% must get above the Earth’s atmosphere Method is robust but you must be patience: Require at least 3 transits preferably 4 with same brightness change, duration and temporal separation Jupiter: 1% area of the Sun (1/100) Earth or Venus 0.01% area of the Sun (1/10,000) GEOMETRY FOR TRANSIT PROBABILITY: 4 GEOMETRY FOR TRANSIT PROBABILITY Not all planetary orbits are aligned along our line of sight to a star Diameter of Sun d* is about 0.01 AU. Diameter of Earth orbit D is 2 AU Random probability of detecting a Sun-Earth analog is about 0.5% So one needs to look at thousands of stars IF all have an Earth Kepler MISSION CONCEPT: 5 Kepler MISSION CONCEPT Kepler Mission is optimized for finding habitable planets ( 0.5 to 10 MÅ ) in the HZ ( near 1 AU ) of solar-like stars Continuously and simultaneously monitor 100,000 main-sequence stars Use a one-meter Schmidt telescope: FOV >100 deg2 with an array of 42 CCD Photometric precision: Noise < 20 ppm in 6.5 hours V = 12 solar-like star => 4s detection for Earth-size transit Mission: Heliocentric orbit for continuous viewing > 4 year duration SEARCH SPACE SENSITIVITY: 6 SEARCH SPACE SENSITIVITY The limit of Kepler for planet detection of planets around a solar-like star is shown by the yellow region Ground based photometry is limited by the Earth’s atmosphere The range of habitable planets (0.5 to 10 MÅ) in the HZ is shown in green. Kepler PHOTOMETER: 7 Kepler PHOTOMETER MECHANICAL DUMMY CCDs: 8 MECHANICAL DUMMY CCDs Used to verify manufacturing processes, alignment tolerances, shake & bake tests, etc. Carrier header cable assembly Sensor Support Fixture E2V and STA CCD’s EARTH-TRAILING HELIOCENTRIC ORBIT: 9 EARTH-TRAILING HELIOCENTRIC ORBIT FIELD OF VIEW IN CYGNUS: 10 FIELD OF VIEW IN CYGNUS • A region of the extended solar neighborhood in the Cygnus region along the Orion arm has been chosen. • The star field is far enough from the ecliptic plane so as not to be obscured by the Sun. EXTENDED SOLAR NEIGHBORHOOD: 11 EXTENDED SOLAR NEIGHBORHOOD The stars sampled are similar to the immediate solar neighborhood. Young stellar clusters, ionized HII regions and the neutral hydrogen, HI, distribution define the arms of the Galaxy. The view is from the north galactic pole looking down onto the galactic plane SCIENCE TEAM: 12 SCIENCE TEAM William Borucki, Principal Investigator, NASA Ames Research Center David Koch, Deputy Principal Investigator, NASA Ames Research Center Co-Investigator’s Working Group G. Basri UC-Berkeley W. Cochran McDonald Obs./U. Texas E. DeVore SETI Institute E. Dunham Lowell Observatory J. Geary SAO R. Gilliland STScI A. Gould Lawrence Hall of Sci/UC-B J. Jenkins SETI Institute Y. Kondo NASA/GSFC D. Latham SAO J. Lissauer NASA/ARC Science Working Group A. Boss Carnegie Institute of Washington T. Brown HAO/NCAR D. Brownlee University of Washington J. Caldwell York University A. Dupree SAO S. Howell Planetary Science Institute G. Marcy UC-Berkeley D. Morrison NASA/ARC T. Owen University of Hawaii H. Reitsema Ball Aerospace D. Sasselov SAO J. Tarter SETI Institute MANAGEMENT TEAM Chet Sasaki, Project Manager at Jet Propulsion Lab Larry Webster, Deputy Project Manager at NASA Ames Research Center Industrial Partner, Ball Aerospace, Boulder, CO SUMMARY: SUMMARY The Kepler Mission will: Observe more than 100,000 dwarf stars continuously for 4 to 6+ years with a precision capable of detecting Earth’s in the HZ The Kepler Mission can discover: Planet sizes from that of Mars to greater than Jupiter Orbital periods from days up to two years About 600 terrestrial planetary systems if most have 1 AU orbits About 1000 inner-orbit giant planets based on already known frequency Can expect 100’s to 1000’s of ??? size planets depending on frequency ??? and orbit ??? A NULL result would also be very significant ! ! ! Results begin 3 months after launch in Oct. 2007 and continue for 4 to 6+ years 13 New Yorker Cartoon: New Yorker Cartoon “Well, this mission answers at least one big question: Are there other planets like ours in the universe?” Drawing by H. Martin; © 1991 The New Yorker Magazine, Inc. 14
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