TRANSIT PHOTOMETRY &
THE KEPLER MISSION
A Search for Habitable Planets
W. Borucki, NASA Ames Research Center,
Moffett Field, CA,
SAO
STScI
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A Search for Habitable Planets
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A Search for Habitable Planets
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TRANSIT PROPERTIES
A Search for Habitable Planets
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VULCAN: GROUND-BASED
SEARCH FOR GIANT PLANETS
A Search for Habitable Planets
Vulcan transit search of 10,000 stars for extrasolar planets
• OBJECTIVES:
• Monitor 10,000 stars
“continuously” for periods of at
least 6 weeks
• Detect jovian-size planets in short
period orbits
• Use Doppler-velocity
measurements to determine
mass and density
• TELESCOPE:
• Aperture: 10 cm
• Focal length: 30 cm
• Field of View: 7x 7 degrees
• Detector: 4096x4096 CCD with 9
pixels
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GIANT PLANET SEARCHES
WITH SMALL TELESCOPES
A Search for Habitable Planets
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HST observation of a jovian-size planet
orbiting the star HD209458
A Search for Habitable Planets
Ten-minute to ten-minute binned data from several orbits have a
precision of 60 ppm (Brown et al. 2001).
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EARTH COMPARED TO
JUPITER
A Search for Habitable Planets
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ULTRAVIOLET IMAGE OF THE SUN
A Search for Habitable Planets
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THE SUN IN VISIBLE LIGHT
A Search for Habitable Planets
Comparison of an
Earth-size planet
with star spots and
plages.
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SOLAR POWER SPECTRUM
A Search for Habitable Planets
(W / m2)2 / cycles / day
10
10
10
10
10
10
10
1 hr
2
Period for terrestrial transit
10
4 hrs
Period
3
24 hrs
12 hrs
27 days
Power spectrum of Sun from SMM data for 1985-1989
1
0
-1
-2
-3
-4
10
-9
10
-8
10
-7
-6
10
10
Frequency, Hz
-5
10
-4
10
-3
The power spectrum of the Sun is very low at the periods
of interest for planetary transits
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CRITICAL QUESTIONS:
A Search for Habitable Planets
•
•
•
•
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?
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MISSION APPROACH
A Search for Habitable Planets
KEPLER: A Wide FOV Photometer that Monitors 100,000 Stars for 4
years with Enough Precision to Find Earth-size Planets in the HZ
Use transit photometry to detect Earth-size
95 cm Schmidt
planets
Corrector (Fused
Silica)
• 0.95 meter aperture provides enough photons
• Observe for several years to detect transit
Focal Plane
patterns
Radiator
• Monitor a single FOV continuously to
avoid missing transits
• Use heliocentric orbit
Graphite Metering
Focal Plane
Electronics
Structure
Get statistically valid
results by monitoring
100,000 stars
• Wide FOV telescope
• Large array of CCD
detectors
1.4m Primary
Mirror
Focal Plane w/ 42
Science CCD’s &
4 Fine Guidance
Sensors
Focus
Mechanism (3)
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AUTOMATED DETECTION
A Search for Habitable Planets
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DETECTIONS VS. PLANET SIZE
AND ORBIT
A Search for Habitable Planets
# of Planet Detections
10000
1000
100
10
1
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
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.
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DISTINGUISHING IRON, ROCKY,
& WATER PLANETS
A Search for Habitable Planets
Fortney et al, submitted 2006
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CANADIAN AND EUROPEAN
PHOTOMETRIC INVESTIGATIONS
MOST; 10 cm Aperture
Launch: on orbit
Capability: few giants in
short period orbits
A Search for Habitable Planets
COROT: 30 cm Aperture
Launched; 12/27/2006
Capability: few terrestrial
planets in short period orbits
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