# Presentation: 102270

## A Fundamental NASA Mission Goal:

**A Fundamental NASA Mission Goal:**

**Q:2 Does life in any form however simple or complex, carbon-based or other, exist elsewhere than on Earth?**
**Are there Earth-like planets beyond our solar system?**

- To place our Solar System in context with other planetary systems

- To provide data on possible platforms for astrobiology beyond our Solar System

- – To place our Sun in context with other solar-like stars

## THE HABITABLE ZONE BY STELLAR TYPES

**T****HE ****H****ABITABLE ****Z****ONE BY ****S****TELLAR ****T****YPES**

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

## PROBING THE RIGHT SEARCH SPACE

**PROBING THE RIGHT SEARCH SPACE**

**The first 50 known extrasolar planets are also 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.**

## 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**

- Transit of Mercury in 2003

- Transit of HD 209458 observed with HST

## The Coming Transit of Venus

## GEOMETRY FOR TRANSIT PROBABILITY

**G****EOMETRY FOR ****T****RANSIT ****P****ROBABILITY**

**Not all planetary orbits are aligned along our line of sight to a star**
**Diameter of Sun d* is about 0.01 AU. Diameter of Earth orbit D is 2 AU**
**Random probability of detecting a Sun-Earth analog is about 0.5%**
**So one needs to look at thousands of stars IF all have an Earth**

## PHOTOMETRY CAN DETECT EARTH-SIZED PLANETS

**P****HOTOMETRY**** ****CAN**** D****ETECT**** E****ARTH-****S****IZED ****P****LANETS**

**The relative change in brightness (********L/L) is equal to the relative areas (A****planet****/A****star****)**
**To measure 0.01% must get above the Earth’s atmosphere**
**This is also needed for getting a high duty cycle**
**Method is robust but you must be patient:**
**	****	****Require at least ****3 transits, preferably 4 ****with same brightness change, **
**	****	****duration and temporal separation**
**	****(the first two establish a possible period, the third confirms it)**

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

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

## Kepler PHOTOMETER

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

**Bandpass: 420-830 nm ;  Exposures: 15 min  (1 min asteroseismology mode)**
**Focal plane and pointing stability are essential. **
**Only 35-pixel “postage-stamps” are read out. Raw pixel data is sent down.**

## CONTINUOUSLY VIEWABLE HIGH DENSITY STAR FIELD

**One region of high star field density far (>55°) from the ecliptic plane where the galactic plane is continuously viewable is centered at RA=19****h****45****m**** Dec=35°. **
**The 55° ecliptic plane avoidance limit is defined by the sunshade size for a large aperture wide field of view telescope in space.**

## Kepler CCDs on the Sky

- Full Moon

## Kepler Fields and Images

- Image is de-focussed to FWHM ~6”

- Each of the 42 CCDs (2048x2048) samples 6 square degrees

## EXTENDED SOLAR NEIGHBORHOOD

**E****XTENDED ****S****OLAR ****N****EIGHBORHOOD**

**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.**
**The view is from the north galactic pole looking down onto the galactic plane**

## EARTH-TRAILING HELIOCENTRIC ORBIT

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

- Due to the cost of the DSN downlink, the # of stars that can be studied drops over the mission from ~150,000 to ~100,000.

- Due to the solar arrays, the spacecraft has to execute a 90-degree role every 3 months. Otherwise, the field is totally fixed.

## KEPLER MISSION TEAM

**KEPLER MISSION TEAM**

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

- _Co-Investigators_
- G. Basri	UC-Berkeley
- W. Cochran	McDonald Obs./U. Texas
- E. DeVore	SETI Institute
- E. Dunham	Lowell Observatory
- 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
- T. Brown	HAO/NCAR
- 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
- Industrial Partner, Ball Aerospace, Boulder, CO

## NUMBER OF DWARF STARS FOR WHICH PLANETS CAN BE DETECTED

**N****UMBER OF ****D****WARF ****S****TARS FOR ****W****HICH ****P****LANETS ****C****AN ****B****E ****D****ETECTED**

**The solid lines show the number of dwarf stars of each spectral type for which a planet of a given radius can be detected at ≥8********. The conservative numbers are based on 4 near-grazing transits with a 1 yr period and stars with V≤14. The dashed lines show a significant increase in the number of stars when assuming 4 near-central transits with a 1-yr period. An even greater increase is realized for 8 near-grazing transits with a 0.5-yr period.**

- Because of the dependence of detection limits on stellar radius, only dwarf stars are desired as targets. This means a pre-launch effort to characterize the quarter-million stars of sufficient brightness in the FOV as to whether they are giants and dwarfs (and get approximate temperatures). This means multi-color photometry and some spectroscopy over 100 square degrees.

## THE VISIBLE SUN HAS DARK & BRIGHT SPOTS

**SOHO/MDI**
**Visible**
**Continuum**
**19-July-2001**

**THE VISIBLE SUN HAS DARK & BRIGHT SPOTS**

## Behavior of Solar Microvariability

- Active Sun

- The total irradiance and visible output of the Sun vary on all timescales because of the magnetic activity (and the convection?)

- Inactive Sun

## TRANSIT SIGNAL VS. SOLAR NOISE

## MOST STARS ARE QUIET ENOUGH

- Variability noise declines with rotation
- Magnetic activity declines
- Spot passage period increases
- Solar-type stars slowed enough by 2-3 Gyr
- Rotation-activity relationship well-known
- Stellar spin-down timescales well-known
- 70% of solar-type stars slow and quiet enough
- Galaxy >10 Gyr old and star formation ~constant
- Detailed galactic population models confirm
- Actual observations of stellar activity confirm

## TRANSIT DETECTABILITY

**Strict periodicity is an extremely powerful filter to dig out transits.**

## Potential for Detections

**Expected # of planets found, assuming one planet of a given size & semi-major axis per star and random orientation of orbital planes.**

**# of Planet**
**Detections**

**Orbital Semi-major Axis (AU)**

## The False-Positives Problem

- There are several common sources of false positives:
- White dwarfs transiting solar-type stars
- Grazing eclipses of one star by another
- Full eclipses in a faint background binary whose light is combined with a foreground bright star
- M dwarfs transiting giants and supergiants

- There are ways to eliminate each of these:
-  Know the spectral type of each target star
-  Multi-(narrow) band photometry of the entire field
-  Test for radial velocity variations (gross, then fine)
-  Measure the transit light curve shape carefully
-  Centroid the variability very carefully (and obtain high resolution images with AO or a space telescope)

## GUEST INVESTIGATOR SCIENCE 

- Magnetic Activity:  short-term behavior, cycles for huge sample; highly relevant for “Sun-Earth connection”
- Fundamental Stellar Parameters: many new eclipsing binaries, asteroseismology (great spectral type coverage)
- Stellar (differential?) rotation for a huge sample; starspots
- Variable Stars: stellar pulsation; behavior of giants and supergiants; dust formation events
- Protoplanetary systems – disks, accretion, magnetic activity
- Interacting binaries, accretion disks and streams, cataclysmic variables and novae
- Quasar and Seyfert galaxy (AGN) variability
- Supernovae?			3000 “postage stamps”

**THE UNEXPECTED.... **
**(unprecedented precision and time coverage)**

## Mission Status

**Status:**
- Phase B was officially started in Oct. 2002.
- Evaluation grade CCDs (electrically functional, but not thinned) were received from the two CCD vendors, STA and E2V, in May 2003.
- Brashear was competitively selected as the vendor for the 1.4 m diameter light-weight primary mirror and the fused-silica Schmidt corrector in May 2003. Corning will be providing both of the pieces of glass.
- System Requirements Review (SRR) was held on 15-17 Oct. 2003. All systems are go!
- Downselection was made to e2v on 28 Oct 2003 as the single supplier of all flight CCDs. e2v has met or exceeded all design requirements to date.
- Future milestones:
- Launch Oct. 2007Critical Design Review (CDR) Aug. 2005Preliminary Design Review (PDR) Oct. 2004

## EXPECTED KEPLER RESULTS

**E****XPECTED ****K****EPLER ****R****ESULTS**

**Hypothesis: all dwarf stars have planets and monitor 100,000 dwarf stars for 4 years**
**Characteristics of host stars:**
**	****Parallax, effective temperature, radius, metallicity, rotation, activity **
**Transits of terrestrial planets around 1AU:**
**	****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 substantially 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**

## SCHEDULE OF RESULTS

## 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.