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Kepler, a Planet Hunting Mission Riley Duren Kepler Chief Engineer Jet Propulsion Laboratory, California Institute of Technology with thanks to Jim Fanson (Kepler Project Manager) for slide contributions Kepler is NASA’s first mission capable of finding Earthsize planets orbiting in the habitable zone of other stars Speculation on the existence of other habitable worlds is age-old [T]here are infinite worlds both like and unlike this world of ours ... we must believe that in all worlds there are living creatures and plants and other things we see in this world.... Epicurus (341-270 BC) Habitable planets must orbit in the “habitable zone” of their parent star Habitable Zone ⇒ water can exist in liquid state Terrestrial Planets (rocky bodies) Gas Giant Planets Trans Neptunian Objects Habitable planets should have mass between about 0.5 Me and 10 Me < 0.5 Me can’t hold on to a life sustaining atmosphere > 10 Me holds on to H & He and becomes a gas giant Mercury Venus Earth Mars Orbit “within” the Habitable Zone of the Sun Kepler will discover planets by observing transits • A transit occurs when a planet passes in front of its star and blocks part of the star’s light. • Earth-size planets produce very small reductions in the star’s brightness (we need to go to space to detect them). – Jupiter would block 1% of the sun’s disk – Earth (or Venus) would block only 0.008% of the sun’s disk Transit of Venus across the Sun The Kepler Spacecraft Photometer Solar Array Spacecraft Bus The Photometer is a wide-angle “Schmidt camera” telescope 0.95 m dia Schmidt Corrector Lens 95 megapixel Camera Sunshade Metering Structure 1.4 m dia Primary Mirror Kepler 95 Megapixel Focal Plane Kepler will monitor 100,000 stars across >100 deg2 of sky Kepler field of view projected onto the sky Kepler’s field of view is >35,000 times larger than the Hubble’s Art copyright Jon Lomberg www.jonlomberg.com Earth-trailing solar orbit provides stable thermal environment and continuous viewing Kepler Ground Segment Elements STScI DSN Madrid ATCA DSN Goldstone DSN Canberra Kepler Launched on a Delta-II Rocket Kepler Launched March 6, 2009 ©2009 Ben Cooper http://www.launchphotography.com Kepler departed the vicinity of the Earth-Moon system within a few days “First Light” Image from Kepler The field of view contains 4.5 million stars NGC 6791 is an open star cluster 13,000 light years from Earth TrES-2 is one of three known Hot Jupiters orbiting stars in the Kepler field of view MOON Kepler’s results will be profound • Kepler will complete a statistically significant census of planets around 100,000 sun-like stars – If such planets are common, Kepler will detect about a hundred – If Kepler detects none, then Earth-like planets are very rare...and we may be alone in the galaxy Sun-like POTENTIALLY HABITABLE PLANETS EARTH-SIZE PLANETS NOT IN THE HZ The planet hunt is on! • • 10 days of calibration data produced first new science result in light curve of known hot Jupiter exoplanet HAT-P7b Planet is so hot (2,650K) it glows like a hot ember Transit signature of planet passing in front of star Sinusoidal light curve due to “phases” of the planet as it orbits star Eclipse of planet passing behind star. This is similar in depth to an Earth-size planet transit. Kepler’s optical phase curve of the exoplanet HAT-P-7b, W.J. Borucki, et al, Science, Vol 325, 7 Aug 2009 Stay Tuned… Kepler Mission Website http://kepler.nasa.gov backup Mission is named in honor of Johannes Kepler (1571-1630) • German mathematician & astronomer • Best known for “Kepler’s laws of planetary motion” 1. 2. 3. Kepler's elliptical orbit law: The planets orbit the sun in elliptical orbits with the sun at one focus. Kepler's equal-area law: The line connecting a planet to the sun sweeps out equal areas in equal amounts of time. Kepler's law of periods: The time required for a planet to orbit the sun, called its period, is proportional to the long axis of the ellipse raised to the 3/2 power. • Successfully predicted the 1631 transits of Mercury & Venus Kepler Project Organization Laboratory for Astronomy & Solar Physics (LASP) -Mission Operations Center Space Telescope Science Institute (STScI) -Data Management Center Ball Aerospace & Technology Corp (BATC) -Spacecraft Prime Contractor NASA Ames Research Center (ARC) -Science Principal Investigator -Science Operations Center ATCA Jet Propulsion Laboratory (JPL) -Project Management -Systems Engineering -Deep Space Network DSN Goldstone DSN Canberra Selection of the Kepler field • Rich in stars but not too crowded (near galactic plane) • Continuous viewing zone (away from ecliptic plane) • Ground based follow-up (Northern hemisphere) Ground-based methods can’t find Earthlike planets orbiting Sun-like stars • About 350 planets are known to orbit other stars. – Most found by the radial velocity method; about a dozen have been found by the transit method – All but a few are gas giants – Most have very short period orbits (“roasters”) – None are “habitable” • Kepler is optimized to find Earth-size (and smaller) planets orbiting in the habitable zone of sun-like stars. http://planetquest1.jpl.nasa.gov/atlas/atlas_index.cfm Kepler in checkout at the Cape Commissioning was accomplished in approximately two months