# Presentation: 511064

## JOHANNES KEPLER

- A guy who’s thought a lot about planets

- ( By permission Sternwarte Kremsmünster)

## Kepler MissionA SEARCH FOR HABITABLE PLANETS

- 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
- 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
- 	Stellar mass determines a stars **temperature** and **size**
- 		type	mass    temp °K	radius
- 		O5	60	42,000	12
- 		B5	  5.9	15,200	  3.9
- 		A0	  2.9	  9,790	  2.4
- 		F0	  1.6	  7,300	  1.5
- 		G2 (Sun)	  1.0	  5,790	  1.0
- 		K0	  0.79	  5,150	  0.85
- 		M2	  0.40	  3,520	  0.50

## STELLAR SIZES AND MASSES

**S****TELLAR ****S****IZES AND ****M****ASSES**

- The mass (in solar masses) and radius (in AU) of dwarf stars, also known as main-sequence stars or luminosity class V, are shown in black.
- The Sun has a radius of 0.00467 AU and a mass of 1 solar mass.
- Giant stars, luminosity class III, of the same spectral type are shown in red.

## THINGS THAT AFFECT TEMPERATURE

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

- 2.	Distance from the star

- 3.  Shape of planet’s orbit
-          circular or elliptical

- 4. 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 AFECTS HABITABILITY

**P****LANET**** S****IZE ****A****FECTS ****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

## PLANETS IN OUR SOLAR SYSTEM

**P****LANETS IN**** O****UR**** S****OLAR**** S****YSTEM**

- 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)

## KEY POINTS FOR THE DESIGN

**K****EY**** P****OINTS FOR THE ****D****ESIGN**

- Stellar type=>HZ=>planet’s orbit
- Planet size =>mass =>life sustaining atmosphere

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

## DETECTING EXTRA-SOLAR PLANTS

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

- 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 *; Uranus	Successful (~150)
- Astrometry	*m *; *D**s ;  a*
- 	Ground: Telescope		Jupiter	Ongoing
- 	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 		Venus	Planned *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)

## SEARCH RESULTS

**S****EARCH ****R****ESULTS**

- 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.

## 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**

## USING PHOTOMETRY TO DETECT PLANETS

**U****SING**** P****HOTOMETRY**** ****TO**** D****ETECT**** P****LANETS**

- Transits
- 	Planet crosses line of sight between
- 	observer and star and blocks
- 	a small amount of light from the star
- Different from occultation or eclipse
- 	Occult means to cover over or to hide
- Photometry
- 	Method of measuring the amount of light
- 	A light meter on a camera is a simple photometer

## 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 M******ISSION***** C****ONCEPT**

*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

## 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**

- (Colors are only meant to represent different sub-systems)

## EARTH-TRAILING HELIOCENTRIC ORBIT

**E****ARTH-****T****RAILING***** *****H****ELIOCENTRIC ****O****RBIT**

- Delta II    2925-10L

## 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.

## SEARCH SPACE IN OUR GALAXY

**S****EARCH**** S****PACE**** ****IN ****O****UR ****G****ALAXY**

- The *Kepler* search will extend out into space along an arm in our galaxy, the Milky Way, for a distance of about 1 kiloparsec or about 3,000 light-years.

**Notes:**
The stars sampled are similar to the immediate solar neighborhood. Young stellar clusters, ionized HII regions and the neutral hydrogen, HI,
 distribution define the arms of the Galaxy. View is from the north galactic pole looking down onto the galactic plane.

## KEPLER  CAPABILITIES

**K****EPLER  ****C****APABILITIES**

- The detectable planet size
- depends on the:
- 	1) Planet’s orbit,
- 	2) Mission duration and
- 	3) Stellar type.
- The dashed red line illustrates, that for a 1-year planetary orbit and a 4-year mission, a 1-Earth-size planet is detectable for a solar like star, G2V (Teff=5780°K).

## 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_
- A. Boss		Carnegie Institute of Washington
- D. Brownlee	University of Washington
- 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**
- Chet Sasaki, Project Manager at  Jet Propulsion Lab
- Larry Webster, Deputy Project Manager at  NASA Ames Research Center
- Len Andreozzi, Program Manager Ball Aerospace, Boulder, CO

## 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 (June 2008)
- 	and will continue for 4 to 6+ years

## New Yorker Cartoon  

*“**Well, this mission answers at least *_*one*_* big question: Are there*
*other planets like ours in the universe?”*

- Drawing by H. Martin; © 1991 The New Yorker Magazine, Inc.

- http://Kepler.NASA.gov