a search for habitable planets kepler mission a s earch for h abitable p lanets (earth-size planets...

A Search for Habitable Planets

Kepler MissionA SEARCH FOR HABITABLE PLANETS

(Earth-size Planets in the Habitable Zone)

Janice Voss

NASA Ames Research Center


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KEY FEATURES

1. Habitable zone =>temperature =>water

2. Planet size =>mass =>atmosphere

Reference: Rare Earth, Ward and Brownlee, Copernicus (Springer-Verlag) ISBN 0-387-98701


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PLANET SIZE AFECTS HABITABILITY

• Too small (about <0.5 M):

Surface gravity g=0.8 G

Can’t hold onto a life sustaining atmosphere (Mercury, Mars)

• Too big (about >10 M):

Surface gravity g=2.2 G

Can hold onto the very abundant light gases (H2 and He) and turn into a gas giant (Jupiter, Saturn, Uranus, Neptune)

(Surface gravity proportional to radius)

Copyright Lynnette Cook


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PLANETS IN OUR SOLAR SYSTEM

Terrestrials Gas giants

Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto

mass 0.055 0.82 1.00 0.11 318 95 14 17 .0002

radius 0.38 0.95 1.00 0.53 11.2 9.4 4.0 3.9 0.18

area 0.15 0.90 1.00 0.28 126 89 16 15 0.03

volume 0.06 0.85 1.00 0.15 1408 844 64 59 0.006

density 0.98 0.95 1.00 0.71 0.24 0.12 0.24 0.32 0.20

(all values are relative to Earth)


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THE HABITABLE ZONE

FOR VARIOUS STELLAR TYPES

The Habitable Zone (HZ) in green is the distance from a star where liquid water is expected to exist on the planets surface. (Kasting, Whitmire and Reynolds, 1993)


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TECHNIQUES FOR FINDING EXTRASOLAR PLANETS

Method Yield Mass LimitStatus

Pulsar Timing m/M ; Lunar Successful (3)

Radial Velocity m sini ; Uranus Successful (~120)

Astrometry m ; Ds ; aGround: Telescope Jupiter OngoingGround: Interferometer sub-JupiterIn developmentSpace: Interferometer Uranus Being studied

Transit Photometry A ; sini=1Ground sub-JupiterHD209458, OGLE TR-

56Space Venus Planned Kepler

Reflection Photometry: albedo*A ; Space Saturn Planned Kepler

Microlensing: f(m,M,r,Ds,DL )Ground sub-Uranus On-going

Direct Imaging albedo*A ; Ds ; a ; MGround Saturn Being studiedSpace Earth Being studied

(Source: J. Lissauer)


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SEARCH RESULTS

The first 50 known extrasolar planets are shown along with the planets in our solar system.

The limit for planet detection using Doppler spectroscopy is shown.The range of habitable planets (0.5 to 10 M) in the HZ is shown in

green.


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USING PHOTOMETRY TO DETECT EARTH-SIZE PLANETS

• The relative change in brightness (L / L) is equal to the relative areas (Aplanet/Astar)

• To measure 0.01% must get above the Earth’s atmosphere

• Method is robust but you must be patient:Require at least 3 transits preferably 4 with same

brightness change, duration (how long the star is dimmer) and period (time between dimmings)

Jupiter: 1% area of the Sun (1/100)

Earth or Venus0.01% area of the Sun (1/10,000)


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Kepler PHOTOMETER

Photometer = CCDs sensors+ TelescopeKepler will be 9th largest Schmidt ever built


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Proto Type CCDs

Views of a prototype module composed of two CCDs mounted to a common carrier

Each CCD is 2200 columns by 1024 rows, thinned, back-illuminated,anti-reflection coated, 4-phase devices manufactured by e2v.

Each CCD has two outputs with the serial channel on the long edge. The pixels are 27 m square, corresponding to 3.98 arcsec on the sky.


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EARTH-TRAILING HELIOCENTRIC ORBIT

QuickTime™ and aTIFF (LZW) decompressorare needed to see this picture.

Delta II 2925-10L


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FIELD OF VIEW IN CYGNUS

A region of the extended solar neighborhood in the Cygnus-Lyra regions along the Orion arm of our galaxy has been chosen.


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The minimum detectable planet size versus planetary orbital period for a 12th magnitude solar-like star (G2), a CDPP of 20 ppm and >4 grazing transits.

(Ref: Koch et al, , Overview and Status of the Kepler Mission, SPIE Conf 5487,p1491-1500 Optical, Infrared, and Millimeter Space Telescopes, J. Mather ed., Glasgow,

Scotland, 2004)

3 mon.

6 mon.

1 yr.

4 yr.6 yr.

A00123456789 0.00.40.81.21.62.02.42.83.23.64.0F0 0.00.20.40.60.81.01.21.41.61.82.0G02.22.4 K00.00.150.30.450.60.750.91.051.21.351.5 M00.00.10.20.30.40.50.60.70.8

2 yr.

KEPLER CAPABILITIES


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EXPECTED RESULTS

Hypothesis: all dwarf stars have planets and monitor 100,000 dwarf stars for 4 years

Transits of terrestrial planets:

About 50 planets if most have R~1.0 R (M~1.0 M)

About 185 planets if most have R~1.3 R (M~2.2 M )

About 640 planets if most have R ~2.2 R (M~10 M )

About 70 cases (12%) of 2 or more planets per system

Transits of thousands of terrestrial planets:If most have orbits much less than 1 AU

Modulation of reflected light of giant inner planets:About 870 planets with periods ≤1 week, 35 with transitsAlbedos for 100 giants planets also seen in transit

Transits of giant planets:About 135 inner-orbit planet detections Densities for about 35 giants planets from radial velocity dataAbout 30 outer-orbit planet detections

Results expected will most likely be a mix of the above


SCHEDULE AND RESULTS

SelectionOrder CCDsOrder opticsLaunchPlanetsp<1 month

Planetsp<3 monthsPreliminary

DesignReview

CriticalDesignReview

Planetsp<1.5 -2 year& Mars-sizep< 3 months

Planetsp<1-1.5 year

Phase C/DPhase E:OperationsExtended mission0 60 70 80 91 01 11 21 30 50 20 30 4CY 0 1CDRPDREnd norm opsEnd ext ops1 4 Phase B

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QuickTime™ and aTIFF (LZW) decompressorare needed to see this picture.


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SCIENCE TEAM

William Borucki, Principal Investigator, NASA Ames Research CenterDavid Koch, Deputy Principal Investigator, NASA Ames Research Center

Co-Investigator’s Working GroupG. Basri UC-BerkeleyT. Brown HAO/NCARW. Cochran McDonald Obs./U.

TexasE. DeVore SETI InstituteE. Dunham Lowell ObservatoryJ. Geary SAO R. Gilliland STScI A. Gould Lawrence Hall of

Sci/UC-BJ. Jenkins SETI InstituteY. Kondo NASA/GSFCD. Latham SAOJ. Lissauer NASA/ARC

Science Working GroupA. Boss Carnegie Institute of

WashingtonD. Brownlee University of WashingtonJ. Caldwell York UniversityA. Dupree SAOS. Howell Planetary Science InstituteG. Marcy UC-Berkeley D. Morrison NASA/ARCT. Owen University of HawaiiH. Reitsema Ball AerospaceD. Sasselov SAO J. Tarter SETI Institute

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.MANAGEMENT TEAM

Chet Sasaki, Project Manager at Jet Propulsion LabLarry Webster, Deputy Project Manager at NASA Ames Research

CenterLen Andreozzi, Program Manager Ball Aerospace, Boulder, CO


SUMMARY

The Kepler Mission will:Observe more than 100,000 dwarf starscontinuously for 4 to 6+ yearswith a precision capable of detecting Earths in the habitable

zone

The Kepler Mission can discover:Planet sizes from that of Mars to greater than JupiterOrbital periods from days up to two yearsAbout 600 terrestrial planetary systems if most have 1 AU

orbitsAbout 1000 inner-orbit giant planets based on

already known frequencyCan expect 100s to 1000s of ??? size planets

depending on frequency ??? and orbit ???A NULL result would also be very significant ! ! !

Results begin 3 months after launch in Oct. 2007 and continue for 4 to 6+ years

More info at http://Kepler.NASA.gov17

a search for habitable planets kepler mission a s earch for h abitable p lanets (earth-size planets...

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