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A Search for Earth-size Planets
Borucki – Page 1
W.J. Borucki & Kepler Team (NASA Ames Research Center)
NASA Academy14 July 2010
A Search for Earth-size Planets
Borucki – Page 2
QUESTIONS TO BE ADDRESSEDBY 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 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
SIMULATION OF FOUR EARTH-SIZED TRANSITS
Diff
eren
tial B
right
ness
0 50 100 150 200 250Elapsed Time (Hours)
1
2
3
4
1+2+3+4
Simulated Transit
10-4 Earth-Sized Transit
5/96
DETECTION OF SMALL SIGNALS IN NOISY DATA
RE
LAT
IVE
B
RIG
HT
NE
SS
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 mincadence & 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
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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 atroom temperature
A Search for Earth-size Planets
Borucki – Page 10
LAUNCH ON MARCH 6, 2009
53-week, Earth-trailing orbitClick to edit Master text stylesSecond 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 withinthe 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.
A Search for Earth-size Planets
Borucki – Page 14
A Search for Earth-size Planets
Borucki – Page 15
A Search for Earth-size Planets
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A Search for Earth-size Planets
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A Search for Earth-size Planets
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UNEXPECTED DISCOVERY: A VERY HOT COMPANION
LIGHT CURVE
OCCULTATION: 1300 ppm
TRANSIT: 500ppm
Star temperature = 9400KCompanion temperature = 12,200KCompanion 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 6819.
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
BR
IGH
TN
ES
S
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.
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