KEPLER William Borucki Principal Investigator NASA Ames Research Center December 13, 2001
SCIENCE TEAM William J. Borucki, PI, and David Koch, Deputy PI Theoretical Studies • Jack Lissauer, NASA Ames • Alan Boss, Carneige Institute Wash. Mission Operations • Donald Brownlee, U. of Washington • Yoji Kondo, NASA GSGC General Overview • John Caldwell, York U. • David Morrison, NASA Ames • Tobias Owen, U of Hawaii • Harold Reitsema, Ball Aerospace Co. • Jill Tarter, SETI Institute Education and Public Outreach • Edna DeVore, SETI Institute • Alan Gould, Lawrence Hall of Science Stellar Occultations & High-Precision CCD Photometry • Timothy Brown, HAO, UCAR • Edward Dunham, Lowell Obs. • John Geary, SAO • Ronald Gilliland, STScI • Steve Howell, U. Ariz • Jon M. Jenkins, SETI Institute Doppler Velocity Planet Searches • William Cochran, UTexas • David Latham, SAO • Geoff Marcy, U. Cal., Berkeley Stellar Variability • Gibor Basri, U. Cal., Berkeley • Andrea Dupree, SAO • Dmiter Sasselov, SAO
KEY QUESTIONS: • Are terrestrial planets common or rare? • How many are in the habitable zone? • What are their sizes & distances? • Dependence on stellar properties
MISSION A wide FOV telescope monitors 100,000 stars for 4 years to detect Earth-size planets Transit Photometry • 0.95 meter aperture • Observe for several years • Monitor stars continuously • Heliocentric orbit Sunshade Electronics CCD’s Schmidt Corrector Statistically valid results • 100,000 stars • Wide field of view telescope • Array of CCD detectors Thermal Radiator Primary Mirror
KEY SCIENCE Sunshade Photometer • Finds hundreds of terrestrial planets • For Earth-size and larger planets, determines: • Frequency • Size distribution • Orbital distribution • Association with stellar characteristics Radiator Solar Array Spacecraft High gain Antenna
SCIENCE DRIVER • Statistically valid result for abundance of Earth-size planets in habitable zone # of Planet Detections Orbital Semi-major Axis (AU) Expected # of planets found, assuming one planet of a given size & semi-major axis per star and random orientation of orbital planes.
SUFFICIENCY OF DATA • Hundreds of terrestrial-size planets will be found if such planets common. Null results significant. • Although 7s detection adequate, Kepler provides 8 s and larger detections • Observation for 4 orbital periods for planets in HZ to validate detections and avoid false alarms • Conduct ground-based programs to select and characterize stars and to rule out false alarms
COMPLETENESS OF THE ANSWER • Kepler provides a robust answer to the frequency of Earth-size and larger planets in and near the habitable zone. • It covers a wide range of planet sizes, orbital distances, and stellar types.
UNIQUENESS • Finds true Earth analogs • Discovers thousands of planets • Characterizes the planetary population within 1.5 AU • Finds associations between stellar types and terrestrial planets
TIMELINESS • Doppler technique has found many giant planets but cannot detect Earth-size planets • Planetary formation models need data on the distributions of rocky planets • New technology enables photometry to discover hundreds of Earth-size planets • Both public and science interest are high
BENEFITS • PUBLIC ENGAGEMENT • Answers question: “Are Earths common or rare in our galaxy?” • US SPACE PROGRAM • Kepler paves the way for TPF by identifying the most promising types of stars and by determining range needed by TPF to find enough targets • Kepler furthers NASA strategic objective: Are there other Earths?
IMPACT ON SPACE SCIENCE • Places Solar System in context with other planetary systems • Places Sun in context with other solar-like stars Q:2 Does life in any form however simpler complex, carbon-based or other, exist elsewhere than on Earth? Are there Earth-like planets beyond our solar system? • Provides new data for astrobiology beyond our Solar System
SOLAR DISK - VISIBLE SOHO/MDI Continuum 19-July-2001
“ACTIVE” SUN QUIET ENOUGH • Solar behavior at Kepler timescales and precision is known • ACRIM, DIARAD, VIRGO on SMM, SOHO • Measured throughout solar cycle • Transits can be seen despite variability • Short durations (~10 hours) • Well-defined shapes and depths • Highly periodic repetitions
MOST STARS QUIET ENOUGH • Variability noise declines with rotation • Magnetic activity declines • Spot passage period increases • Solar-type stars slowed enough by 2-3 Gyr • Rotation-activity relationship well-known • Stellar spin-down timescales well-known • 70% of solar-type stars slow and quiet enough • Galaxy >10 Gyr old and star formation ~constant • Detailed galactic population models confirm • Actual observations of stellar activity confirm
GUEST INVESTIGATOR SCIENCE • Activity levels, short-term behaviors, and cycles for huge sample highly relevant for “Sun-Earth connection” • Protoplanetary systems – disks, accretion, magnetic activity • Stellar rotation periods for a huge sample • Variables; stellar pulsation; behavior of giants and supergiants; dust formation events • Interacting binaries, accretion disks and streams, cataclysmic variables and novae • Many new eclipsing binaries • Quasar and Seyfert galaxy (AGN) variability • THE UNEXPECTED…. • (unprecedented precision and time coverage)
DATA: SOLAR SYSTEM A great deal of information, But… • Single example. • Biased example – We are here! Terrestrial Planets Meteorites Giant Planets Comets Asteroids Moons
DATA: EXTRASOLAR PLANETS • ~ 10% of sunlike stars have giant planets within 2 AU. • At least one such (probably all) is a gas giant. • > 30% of sunlike stars don’t have a true Jupiter analog (but may have a “Saturn” at 5 AU &/or a “Jupiter” at 10 AU). • Pulsars can host terrestrial mass planets.
MODELS OF PLANET FORMATION • Strive to reproduce observations. • Are not predictive: • Uncertainties in initial conditions • Fundamental processes complex and chaotic (turbulence/viscosity, sticking of grains, gap formation/planetary migration)
PLANET SYSTEM STRUCTURE Observations + Theory = Conclusions: Between 0% and 90% of sunlike stars have planetary systems like our Solar System. We have a great deal to learn!
SIGNIFICANCE OF DISCOVERIES • Finds true Earth analogs or shows they are rare • Finds close-in planets even if small and infrequent. • Sizes, frequencies, periods of terrestrial planets. • Planetary characteristics vs. stellar spectral type. • Terrestrial planets in multiple star systems. • Relationship between “Earths” and “Jupiters”. • Densities of giant planets. • Albedos/phase functions of “hot Jupiters”.
SUMMARY • Detect true Earth analogs (or show that they are rare). • Characterize the distribution of terrestrial planets. • Determine the properties of stars (single & multiple) hosting planets. Kepler is uniquely qualified to detect Earth-like extrasolar planets “before this decade is out”!