a search for earth-size planets borucki – page 1 roger hunter (ames research center) & kepler...
TRANSCRIPT
A Search for Earth-size Planets
Borucki – Page 1
Roger Hunter (Ames Research Center)
& Kepler TeamMarch 26, 2010
A Search for Earth-size Planets
Borucki – Page 2
A Search for Earth-size Planets
Borucki – Page 3
CRITICAL QUESTIONS:
• 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 4
THE HABITABLE ZONE FOR VARIOUS STELLAR SPECTRAL TYPES
A Search for Earth-size Planets
Borucki – Page 5
PLANETS ARE DIFFICULT TO DETECT
A Search for Earth-size Planets
Borucki – Page 6
THE SUN IN VISIBLE LIGHT
Earths are mucheasier to find whenUV light is blocked.
Comparison of anEarth-size planet withstar spots and plages.
Rapid motion and uniform repetition distinguishes planets from spots.
A Search for Earth-size Planets
Borucki – Page 7
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
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 • 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 8
SPACECRAFT & 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 9
LAUNCH ON MARCH 6, 2009
Borucki – Page 10 8
A Search for Habitable Planets
STScISAO
Continuously Monitor >100,000 Stars
Use a 1 m Schmidt telescope with a FOV >100 deg2
DGK
A Search for Earth-size Planets
Borucki – Page 11
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 (84 parts per million change in brightness)
Transit of Venus across the Sun
A Search for Earth-size Planets
Borucki – Page 12
KEPLER MISSION DATA FLOW
Calibrated PixelsCalibrated Light Curves
RawPixels
RawData
12
Deep Space NetworkCanberra/Madrid/Goldstone
Science Operations CenterNASA A.R.C.
Moffett Field, CA
& PLANETS!
Mission Operations CenterLASP
Boulder, CO
Space Telescope Science Institute, Baltimore, MD
A Search for Earth-size Planets
Borucki – Page 13
OBSERVATIONS
• 9.7 days of calibration observations of 56,000 bright stars of all types began on 1 May 2009
• Science operations began on 12 May with observations of 156,000 mostly dwarf stars plus;– 1000 red giants for astrometry/parallax measurements– 1700, mostly variable, bright stars for astroseismology at 30 min
cadence– 450, mostly variable, bright stars for asteroseismology at 1 min cadence
• Data presented here is based on the first 43 days of observations
• Over one hundred candidate planets, several hundred eclipsing binaries, and thousands of variable stars are visible in these data.
A Search for Earth-size Planets
Borucki – Page 14
HAT-P-7b Ground vs. Space
14
A. Pal et al., 2008