A Search for Earth-size Planets Borucki – Page 1 W.J. Borucki & Kepler Team (NASA Ames Research...

A Search for Earth-size Planets

Borucki –

W.J. Borucki & Kepler Team (NASA Ames Research Center)

NASA Academy14 July 2010


Borucki –

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?


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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


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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.


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EARTH COMPARED TO THE SUN; EARTHS ARE REALLY HARD TO FIND


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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.


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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)


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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 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


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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 atroom temperature


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LAUNCH ON MARCH 6, 2009

53-week, Earth-trailing orbitClick to edit Master text stylesSecond level

Third level Fourth level

Fifth level


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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.


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M* = 1.3 MSun

Mplanet = 3.9 ± 0.19 MJupiter

= 6.31 g/cm3

IS IT A PLANET OR A FALSE POSITIVE?


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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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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.


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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.


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SUCCESSOR MISSIONS WILL SEARCH FOR BIOGENIC GASES

Infrared spectrum with and without an atmosphere

WAVELENGTH

BR

IGH

TN

ES

S


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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.

A Search for Earth-size Planets Borucki – Page 1 W.J. Borucki & Kepler Team (NASA Ames Research...

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