# Presentation: 313814

## JOHANNES KEPLER

- A guy who’s thought a lot about planets

- ( By permission Sternwarte Kremsmünster)

## Kepler MissionA SEARCH FOR HABITABLE PLANETS

- Night Sky Network Presentation
- November 16, 2006
- David Koch
- NASA Ames Research Center

## OVERVIEW

**O****VERVIEW**

- What makes for a Habitable Planet
- Different Methods for Finding Planets
- Planets Discovered to Date
- Transit Photometry
*Kepler Mission* Concept
- Expected Results

## WHAT DOES HABITABLE MEAN TO YOU?

**W****HAT**** D****OES**** H****ABITABLE**** M****EAN**** ****TO**** Y****OU****?**

- Right temperature
- Air
- Liquid water
- Light to keep you warm and to see
- Radiation shield
- Asteroid protection

**Notes:**
Before designing an experiment, you need to ask yourself “What am I looking for?”

## THINGS THAT AFFECT TEMPERATURE

**T****HINGS**** T****HAT**** A****FFECT**** T****EMPERATURE**

- Want temperature so you can have liquid water on the surface of the planet

- Temperature of star
- Distance from the star
- Shape of planet’s orbit:  circular or elliptical
- Planet’s atmosphere: greenhouse gases

-      These define the Habitable Zone (HZ) for a star

## THE HABITABLE ZONE FOR VARIOUS STELLAR TYPES

**T****HE ****H****ABITABLE ****Z****ONE ****FOR ****V****ARIOUS ****S****TELLAR ****T****YPES**

- 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)

**Notes:**
More specifically, the continuously habitable zone

## WHAT IS IMPORTANT ABOUT AN ATMOSPHERE?

**W****HAT**** I****S**** I****MPORTANT**** A****BOUT**** A****N**** A****TMOSPHERE****?**

- Composition (Earth)
- 	free oxygen (about 23%)
- 	mostly inert (about 75% nitrogen)
- 	very little toxic gases
- Composition affects temperature
- 	Minimize day-night extremes
- 	Greenhouse gases (water, CO2) hold in the heat
-  Acts as an invisible protective shield
- 	Cosmic rays (high energy gamma-rays, protons, electrons)
- 	Solar wind and solar flares (charged particles)
- 	UV - ultraviolet
- 	Micrometeoroids (e.g., puts holes in Space Shuttle window)
-  Transports water
- 	Rain

## PLANET SIZE AFFECTS HABITABILITY

**P****LANET**** S****IZE ****A****FFECTS ****H****ABITABILITY**

- Planets form by accretion from a disk of gas and dust
- Too small (about <0.5 M):
- 		Can’t hold onto a life sustaining 		atmosphere (Mercury, Mars)
- 		surface gravity g<0.8 G
- Too big (about >10 M):
- 		Can hold onto the very abundant light 	gases (H2 and He) and turn into a gas 	giant (Jupiter, Saturn, Uranus, Neptune)
- 		 surface gravity g>2.2 G
- 	(Surface gravity proportional to radius)

- Copyright Lynnette Cook

## KEY POINTS THAT GUIDE THE SEARCH

**K****EY**** P****OINTS THAT ****G****UIDE THE ****S****EARCH**

- Stellar type => Which stars to search
- HZ => Orbital periods and how long to look
- Planet sizes => Sensitivity or precision needed

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

## DETECTING EXTRA-SOLAR PLANETS

**D****ETECTING**** E****XTRA-****S****OLAR ****P****LANETS**

- That is,
- Planets orbiting other stars

## TECHNIQUES FOR FINDING EXTRASOLAR PLANETS

**T****ECHNIQUES FOR ****F****INDING ****E****XTRASOLAR ****P****LANETS**

- _Method__	__Yield__	__Mass Limit__	__Status_
- Pulsar Timing	*m/M* ; Lunar	Successful (3)
- Radial Velocity	*m * sin*i *; super-Earth	Successful (~200)
- Astrometry	*m *; *D**s ;  a*
- 	Ground: Interferometer	sub-Jupiter	In development
- 	Space: Interferometer	Uranus	Being studied
- Transit Photometry	*A *; sin*i=1*
- 	Ground 		sub-Jupiter	HD209458, OGLE TR-56
- 	Space (2006)		sub-Jupiter	HST (~16)
- 	Space (2006, 2008)		Venus	Planned CoRoT, *Kepler*
- Reflection Photometry: 	*albedo***A *; 
- 	Space	Saturn	Planned *Kepler*
- Microlensing: 	f(*m,M,r,D**s**,D**L *)
- 	Ground		sub-Uranus	On-going
- Direct Imaging	*albedo***A *;  *D**s **; **a ; M*
- 	Ground		Saturn	Being studied
- 	Space		Earth	Being studied
- (Source: J. Lissauer)

## WE NEED A DIFFERENT APPROACH

**W****E**** N****EED**** ****A**** D****IFFERENT**** A****PPROACH**

- Radial velocity (Doppler spectroscopy) method unable to detect Earth-size planets
- Earth-like planets are about 300 times less massive and about 100 times smaller in area than Jupiter
- Need a different approach that can detect smaller planets
- No method exists for detecting habitable planets from ground-based observatories
- The *Kepler Mission* uses photometry to detect transits and can detect Earth-size planets from space
**The *****Kepler Mission***** is optimized to detect habitable planets in the habitable zone of solar-like stars**

- Exoplanet encyclopedia http://exoplanet.eu

## USING PHOTOMETRY TO DETECT EARTH-SIZE PLANETS

**U****SING**** P****HOTOMETRY**** ****TO**** D****ETECT**** E****ARTH-****S****IZE ****P****LANETS**

- 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 patience:
- 		Require at least 3 transits preferably 4 with same 			brightness change, duration and temporal separation

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

- Earth or Venus
- 0.01% area of the Sun (1/10,000)

## Kepler MISSION CONCEPT

*Kepler Mission* is optimized for finding
- 	habitable planets ( 0.5 to 10 M )
- 	in the HZ ( near 1 AU ) of solar-like stars
- Continuously and simultaneously
- 	monitor 100,000 main-sequence stars
- Use a one-meter Schmidt telescope:
- 	FOV >100 deg2 with an array of 42 CCD
- Photometric precision:
- 	Noise < 20 ppm in 6.5 hours V = 12 solar-like star
- 	=> 4 detection for Earth-size transit
- Mission:
- 	Heliocentric orbit for continuous viewing
- 	 _>_ 4 year duration

## Kepler PHOTOMETER

***Kepler *****P****HOTOMETER**

- Photometer = CCDs sensors+ Telescope
*Kepler* will be 9th largest Schmidt ever built
- and the largest telescope launched beyond earth-orbit

## Proto Type CCDs

**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.

## Kepler SPACECRAFT

***Kepler *****S****PACECRAFT**

## FIELD OF VIEW IN CYGNUS

**F****IELD OF ****V****IEW IN ****C****YGNUS**

- A region of the extended solar neighborhood in the Cygnus-Lyra regions along the Orion arm of our galaxy has been chosen. Located on one side of the summer triangle (Deneb-Vega-Altair)

## EXPECTED RESULTS

**E****XPECTED ****R****ESULTS**

- 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 transits
- 	Albedos 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 data
- 	About 30 outer-orbit planet detections
- Results expected will most likely be a mix of the above

## SCHEDULE AND RESULTS

## SCIENCE TEAM

**S****CIENCE ****T****EAM**

- William Borucki, Principal Investigator, NASA Ames Research Center
- David Koch, Deputy Principal Investigator, NASA Ames Research Center

- _Co-Investigator’s Working Group_
- G. Basri	UC-Berkeley
- T. Brown	HAO/NCAR
- J. Christensen-Dalsgaard
- 		U. Aarhus, Denmark
- W. Cochran	McDonald Obs./U. Texas
- E. DeVore	SETI Institute
- E. Dunham	Lowell Observatory
- T. N. Gautier	JPL
- J. Geary	SAO
- R. Gilliland	STScI
- A. Gould	Lawrence Hall of Sci/UC-B
- J. Jenkins	SETI Institute
- Y. Kondo	NASA/GSFC
- D. Latham	SAO
- J. Lissauer	NASA/ARC

- _Science Working Group_
- N. Batalha	San Jose State University
- A. Boss		Carnegie Institute of Washington
- D. Brownlee	University of Washington
- D. Caldwell	SETI Institute
- J. Caldwell	York University
- A. Dupree	SAO
- S. Howell	Planetary Science Institute
- G. Marcy	UC-Berkeley
- D. Morrison	NASA/ARC
- T. Owen	University of Hawaii
- H. Reitsema	Ball Aerospace
- D. Sasselov	SAO
- J. Tarter	SETI Institute

**M****ANAGEMENT ****T****EAM**
- Leslie Livesay, Project Manager at Jet Propulsion Lab
- Monte Henderson, Program Manager Ball Aerospace, Boulder, CO
**www.Kepler.NASA.gov **

## SUMMARY

- The *Kepler Mission* will:
- Observe more than 100,000 dwarf stars
- continuously for 4 to 6+ years
- with a precision capable of detecting Earth’s in the HZ
- The *Kepler Mission *can discover:
- Planet sizes from that of Mars to greater than Jupiter
- Orbital periods from days up to two years
- About 600 terrestrial planetary systems if most have 1 AU orbits
- About 1000 inner-orbit giant planets based on
- 	already known frequency
- Can expect 100’s to 1000’s of  **???** size planets
- 	depending on frequency **???** and orbit **???**
- A NULL result would also be very significant ! ! !
- Results expected 3 months after launch (November 2008)
- 	and will continue for 4 to 6+ years

- http://kepler.nasa.gov