Borucki – Page 1 8

A Search for Habitable Planets

STScISAO

TRANSIT PHOTOMETRY &

THE KEPLER MISSION

W. Borucki, NASA Ames Research Center,Moffett Field, CA,

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TRANSIT PROPERTIES

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VULCAN: GROUND-BASED

SEARCH FOR GIANT 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

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HST observation of a jovian-size planet

orbiting the star HD209458

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

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ULTRAVIOLET IMAGE OF THE SUN

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THE SUN IN VISIBLE LIGHT

Comparison of anEarth-size planetwith star spots andplages.

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The power spectrum of the Sun is very low at the periods

of interest for planetary transits

SOLAR POWER SPECTRUM

Power spectrum of Sun from SMM data for 1985-1989

24 h

rs

27 d

ays

12 h

rs

4 h

rs

1 h

rPeriod3

10(W

/ m

2)2

/ c

ycle

s /

da

y

100

-110

-210

-310

-410

210

110

Frequency, Hz

-710

-810

-610

-510

-410

-310

-910

Period f

or

terr

estr

ial tr

ansit

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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?

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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 FOV continuously to

avoid missing transits

• Use heliocentric orbit

MISSION APPROACH

KEPLER: A Wide FOV Photometer that Monitors 100,000 Stars for 4

years with Enough Precision to Find Earth-size Planets in the HZ

Get statistically valid

results by monitoring

100,000 stars

• Wide FOV telescope

• 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

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AUTOMATED DETECTION

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DETECTIONS VS. PLANET SIZE

AND ORBIT

Expected # of planets found, assuming one planet of a given size & semi-major

axis per star and random orientation of orbital planes.

# o

f P

lan

et D

etec

tion

s

Orbital Semi-major Axis (AU)

10000

1000

100

10

10.2 10 1.40.4 1.20.80.6 1.6

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DISTINGUISHING IRON, ROCKY,

& WATER 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

COROT: 30 cm Aperture

Launched; 12/27/2006

Capability: few terrestrial

planets in short period orbits