A Search for Earth-size Planets Borucki – Page 1 W.J. Borucki & Kepler Team (NASA Ames Research Center) NASA Academy 14 July 2010

A Search for Earth-size Planets Borucki – Page 2 QUESTIONS TO BE ADDRESSED BY THE KEPLER MISSION Are terrestrial planets common or rare? What are their sizes & distances? How often are they in the habitable zone? What is their dependence on stellar properties?

A Search for Earth-size Planets Borucki – Page 3 THE HABITABLE ZONE DEPENDS ON STAR TYPE Requirements for habitable planets Rocky planet with a surface Atmosphere to prevent loss of water to space Plate tectonics to maintain atmospheric composition. Temperature appropriate for liquid water Nearly circular orbit to avoid temperature extremes. Large moon to prevent polar wandering Long-lived star to provide time for evolution

A Search for Earth-size Planets Borucki – Page 4 A PATTERN OF TRANSITS CAN BE USED TO DETECT EARTH-SIZE PLANETS From TRANSIT DATA obtain: Duration, depth, orbital period and inclination. Derive planet sizes and orbital radii (when combined with stellar information) From ENSEMBLE of PLANETARY SYSTEMS obtain: Estimates frequency of planet formation for inner planets. Requires thousands of stars because most orbits won’t be aligned properly ADDITIONAL SCIENCE: Frequency of Maunder minimums and the implications for the Sun and Earth’s climate.

A Search for Earth-size Planets Borucki – Page 5 EARTH COMPARED TO THE SUN; EARTHS ARE REALLY HARD TO FIND

A Search for Earth-size Planets Borucki – Page 6 THE SUN IN VISIBLE LIGHT Earths are much easier to find when UV light is blocked. Comparison of an Earth-size planet with star spots and plages. Rapid motion and uniform repetition distinguishes planets from spots.

A Search for Earth-size Planets Borucki – Page 7 DETECTION OF SMALL SIGNALS IN NOISY DATA RELATIVE BRIGHTNESS ELAPSED TIME (hours)

A Search for Earth-size Planets Borucki – Page 8 Use transit photometry to detect Earth-size planets 0.95 meter aperture provides enough photons Observe for several years to detect transit patterns Monitor a single large area on the sky continuously to avoid missing transits Use heliocentric orbit Up to 170,000 targets at 30 min cadence & 512 at 1 min INSTRUMENT DESIGN KEPLER: A Wide Field-of-View Photometer that Monitors ≥100,000 Stars for 3.5 yrs with Enough Precision to Find Earth-size Planets in the Habitable Zone Get statistically valid results by monitoring 100,000 stars with; Wide Field-of-view telescope (100 sq deg) Large array of CCD detectors 1.4m Primary Mirror Focus Mechanism (3)‏ Focal Plane Radiator Graphite Metering Structure 95 cm Schmidt Corrector (Fused Silica)‏ Focal Plane w/ 42 Science CCD’s & 4 Fine Guidance Sensors Focal Plane Electronics

A Search for Earth-size Planets Borucki – Page 9 Click to edit the outline text format Second Outline Level  Third Outline Level Fourth Outline Level  Fifth Outline Level  Sixth Outline Level  Seventh Outline Level  Eighth Outline Level  Ninth Outline LevelClick to edit Master text styles  Second level  Third level  Fourth level  Fifth level Click to edit the outline text format Second Outline Level  Third Outline Level Fourth Outline Level  Fifth Outline Level  Sixth Outline Level  Seventh Outline Level  Eighth Outline Level  Ninth Outline LevelClick to edit Master text styles  Second level  Third level  Fourth level  Fifth level SPACECRAFT & INSTRUMENT Optical pass band of the Kepler instrument Largest focal plane for a NASA flight mission: 94.6 million science pixels 42 science CCDs, 2 channels each 4 fine guidance sensor (FGS) CCDs CCDs controlled at -85C, Readout electronics at room temperature

A Search for Earth-size Planets Borucki – Page 10 LAUNCH ON MARCH 6, week, Earth-trailing orbit Click to edit Master text styles Second level Third level Fourth level Fifth level

A Search for Earth-size Planets Borucki – Page 11 KEPLER HAS THE PRECISION TO FIND EARTHS & IT IS THE FIRST TO DISCOVER LIGHT FROM THIS PLANET Measurement scatter is within the line thickness. Magnification by 7 shows transits + occultation Occultation is the size of a transit by Earth-size planet. Rise in light between transits is discovery of light from the planet itself.

A Search for Earth-size Planets Borucki – Page 12 M* = 1.3 MSun Mplanet = 3.9 ± 0.19 MJupiter  = 6.31 g/cm3 IS IT A PLANET OR A FALSE POSITIVE?

A Search for Earth-size Planets Borucki – Page 13 ACTIVE-OPTICS IMAGE OF THE TARGET “STAR” SHOWS IT TO BE TWO STARS The fact that there are two stars instead of one makes it difficult to determine the size of the planet and its distance from its star and therefore whether it is in the habitable zone.

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A Search for Earth-size Planets Borucki – Page 18 UNEXPECTED DISCOVERY: A VERY HOT COMPANION LIGHT CURVE OCCULTATION: 1300 ppm TRANSIT: 500ppm Star temperature = 9400K Companion temperature = 12,200K Companion size = 0.8 RJ An investigation of the phenomenon is underway.

A Search for Earth-size Planets Borucki – Page 19 ASTEROSEISMOLOGY RESULTS PROVIDE INFORMATION ON THE SIZE AND AGES OF STARS & PLANETS Frequency-power spectra of three solar-like stars. Color-magnitude diagram for NGC Kepler results are a major improvement over all prior observations. Young, rapidly oscillating stars. Old, slowly pulsating stars.

A Search for Earth-size Planets Borucki – Page 20 SUCCESSOR MISSIONS WILL SEARCH FOR BIOGENIC GASES Infrared spectrum with and without an atmosphere WAVELENGTH BRIGHTNESS

A Search for Earth-size Planets Borucki – Page 21 SUMMARY By 2013, Kepler should: Determine the frequency of Earth-size planets, Determine whether Earths in the Habitable Zones of other stars are common or rare. Provide important precursor science for a flagship exoplanet mission in the future Determine the fate of Star Trek KEPLER IS THE NEXT STEP IN OUR SEARCH FOR MANKIND’S PLACE IN THE MILKY WAY.