a search for habitable planets dk 10/07 finding habitable planets the kepler mission david koch nasa...

A Search for Habitable Planets

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Finding Habitable PlanetsThe Kepler Mission

David Koch

NASA Ames Research Center


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OVERVIEW

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• Scientific Goals

• Mission Requirements

• Kepler Star Field

• Follow-up Observing

• Expected Results

• Photometer

• Science Team

• Status


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What is it we are looking for?

• Planets form out of a disk of gas and dust left over from star formation.

• If mass too small, less than about 1/2 M then it can’t hold onto a life sustaining atmosphere (Mercury, Mars)

• If mass too big, greater than about 10 M then it can hold onto the very abundant light gases (H2 and He) and turn into a gas giant (Jupiter, Saturn, Uranus, Neptune)

So, to find habitable planets we need … a system capable of

finding Earth-size planets (0.8<R<2.2)

And, is able to find them in the habitable zone, i.e., in an orbit where liquid water can exist on the surface of the planet.

Copyright Lynnette Cook

DERIVING THE SCIENTIFIC REQUIREMENTS

Kepler is specifically designed to search for habitable planets (0.5 to 10 M) in the HZ (near 1 AU for solar-like stars)


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Kepler GOALS

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Explore the structure and diversity of extra-solar planetary systems

1.Determine the frequency of terrestrial and smaller planets in or near the habitable zone of a wide variety of spectral types of stars;

2.Determine the distributions of size and semi-major axis of these planets;

3.Estimate the frequency and orbital distribution of planets in multiple-star systems;

4.Determine the distributions of semi-major axis, albedo, size, mass and density of short-period giant planets;

5.Identify additional members of each photometrically discovered planetary system using complementary techniques; and

6.Determine the properties of those stars that harbor planetary systems.


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Current State of Affairs

Finding Earth-size planets in the HZ is well beyond current capabilities Note: Masses are only lower limits except for transit cases and statistically about 2x greater than

shown


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The Kepler approach to detecting planets is to measure the change in brightness of stars caused by planetary transits

• To measure 80 ppm, you need to be above the Earth’s atmosphere

• The probability for alignment is about 0.5% for an Earth-like orbit So… you need to observe lots of stars

• 3.5+ yr mission is required to detect at least 3 transits preferably 4

• Must be robust to false positives: Able to reject background eclipsing binaries, grazing binaries andrequire repeatable transit depth, duration and temporal separation

Jupiter: 1% area of the Sun

Earth or Venus0.008% area of the Sun (80 ppm)

What Are The Design Requirements?


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THE MISSION DESIGN

• Photometric precision of 20 ppm 4for V=12 solar-like star in 6.5 hours

• Continuously and simultaneouslymonitor 100,000 solar-like stars

• A one-meter aperture Schmidt telescopefield of view >100 deg2

• A focal plane array of 42 CCDwith a total of 95 mega-pixels

• Launch into an Earth-trailing orbitto permit continuous viewing

• Observe same star field for 3.5+ years

• Analyze data for a sequence of transits


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STAR FIELD IN CYGNUS

The Kepler star field is a part of the extended solar neighborhood in the Cygnus-Lyra regions along the Orion arm. It is located on one side of the summer triangle

(Deneb-Vega-Altair)


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Follow-Up Observing Plan

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1. Cross check for internal consistency of Kepler data a. Individual transits consistent in amplitude and durationb. Individual pixels of psf consistent within statistics for each cadencec. Differential Image Analysis not show shift in position

2. Check catalogs for nearby stars, background eclipsing

binary3. Perform moderate resolution spectroscopy

a. Eliminate white dwarf or grazing eclipsing binaryb. Improve knowledge of mass and size of the parent star

4. Perform high-precision radial-velocity observations with HIRES, HET and HARPS-North:

a. Measure mass or upper limit to mass (get density)b. Detect companion non-transiting giant planets in system


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Follow-Up Capability of HARPS-North

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Mass uncertainty for HARPS-North assuming a non-active, slowly-rotating G2V star with V=12, 50 hours of observing optimized for the known period and phase


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EXPECTED RESULTS

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What will Kepler Mission discover?• Planets with sizes from that of Mars to Jupiter

with orbital periods from a few days up to two years

• Can expect 100’s to 1000’s of ??? size planets depending on frequency ???, stellar type and orbit ???

• About 600 terrestrial planetary systems if most have orbits like Earth (M < 10 M )

• About 50 transiting short-period giant planets based on their already known frequency

• A NULL result would also be very significant !Also…• Astrometric distances to Kepler stars (derive size)• Astereoseismology for about 5-6000 stars (derive

mass)


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Photometer Components

Dust Cover

1.4 m Primary Mirror

Focal PlaneRadiator

Sunshade

Lower TelescopeHousing

Focus MechanismAssy (3)

CCD Detectors

(42)

Focal Plane Array Assbly

UpperTelescopeHousing

0.95 m Schmidt

Corrector

Aft Bulkhead


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SCIENCE TEAM

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

Co-Investigator’s Working GroupG. Basri UC-BerkeleyT. Brown Las Cumbres Obs Global

TelJ. Christensen-Dalsgaard

U. Aarhus (Denmark)W. Cochran McDonald Obs./U. TexasE. DeVore SETI InstituteE. Dunham Lowell ObservatoryT. N. Gautier JPLJ. 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 GroupN. Batalha San Jose State UniversityA. Boss Carnegie Institute of

WashingtonD. Brownlee University of WashingtonD. Caldwell SETI InstituteJ. Caldwell York University (Canada)A. Dupree SAOS. Howell Nat’l Optical Astronomy

Observ.G. Marcy UC-Berkeley D. Morrison NASA/ARCT. Owen University of HawaiiH. Reitsema Ball AerospaceD. Sasselov Harvard UniversityJ. Tarter SETI Institute

MANAGEMENT TEAMLeslie Livesay, Project Manager at Jet Propulsion LabAlan Frohbieter, Program Manager at Ball Aerospace, Boulder, CO


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Status

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• Recent program pressures forced, among other things, a decrease in mission life from 4 to 3.5 years. But the capability still exists to extend the mission life.

• Completed environmental testing and characterization of focal plane array (42 CCDs and electronics). Telescope is ready.

• Currently performing spacecraft and photometer assembly.• Flight software has finished qualification testing• Integration of photometer and spacecraft to begin in the Spring

of 2008• Launch is scheduled for Feb. 2009• Plan is to operate for 3.5+ years

2009 will be the 400th anniversary of Kepler’s publication of Astronomia Nova describing

his first and second laws of planetary motion and it is the International Year of Astronomy


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Summary

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The Kepler Mission is…

NASA’s first mission capable of finding Earth-size and smaller planets in the habitable zone of other stars.

http://Kepler.NASA.gov

a search for habitable planets dk 10/07 finding habitable planets the kepler mission david koch nasa...

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