Search for & Characterizing Small Planets with NASA s Kepler Mission

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1 Search for & Characterizing Small Planets with NASA s Kepler Mission Eric Ford University of Florida SAMSI Astrostatistics Workshop September 21, 2012 Image credit: NASA/ESA/StSci

2 Golden Age for Planet Discovery Image credit: Jorge Gallego

3 Questions We d Like To Answer How common is life beyond the Solar System in the Universe? What is the distribution of planets and planetary systems? How does planet formation work?

4 Refining the Question How common is life beyond the Solar System in the Universe? How common is Earth-like life in the Milky Way (MW; i.e., our galaxy)? How common are Earth-like planets in MW? How common are Earth-size (or Earth-mass) planets in the habitable zone of solar-type stars in MW?

5 Questions Kepler Can Answer How common are Earth-size planets in the habitable zone of solar-type stars in MW? What is the relationship between mass, radius & density for small planets? (i.e., constraints on bulk composition? What are the empirical constraints on theories of planet formation?

6 Questions Kepler Can Answer How common are Earth-size planets in the habitable zone of solar-type stars in MW? Planet detection & confirmation, understanding selection function What is the relationship between mass, radius & density for small planets? (i.e., constraints on bulk composition) Analysis of TTVs What are the empirical constraints on theories of planet formation? Comparing observations of exoplanet population to synthetic planet populations

7 NASA s Kepler Mission Photometry of >160,000 stars Looking for Earth-like planets in transit 50µmag in 6 hours; 30 minute cadence All current data public as of Oct 28, year Extended mission will yield ~2TB of light curves (much more pixel data) N NASA

8 NASA/Ames/JPL-Caltech

9 Detecting a Transiting Planet NASA/Kepler/Dana Berry

10 Transiting Planet Detection w/ Kepler For most practical purposes, searching for planet transits is a solved problem for sufficiently large planets (>~2 R Earth ) Still a challenge for Earth-size planets in HZ But making a real contribution to planet detection (or validation) would require extensive astronomical/instrument knowledge

11 NASA

12 Kepler s Planet Candidates as of Dec 2011 Feb 2011 Dec 2011 Size Relative to Earth Jun 2010 Orbital Period in days Batalha et al NASA

13 Potential False Positives & Validation For expected rates see: Borcuki et al. 2011b Morton & Johnson 2011 Howard et al. 2011

14 Transiting Planet Characterization Planet s Size, Mass & Density Basis for theorists to consider bulk composition, size of any atmosphere, implications for habitability Planet s Orbit (period, eccentricity, inclination) Relationship to masses and orbits of any other planets orbiting the same star Basis for theorists to constrain planet formation models

15 Systems w/ Multiple Transiting Planets Brightness Image credit: NASA Ames/Kepler Time (days)

16 Image credit: NASA/Tim Pyle

17 Kepler-11 Lissauer, Fabrycky, Ford et al. 2011

18 Kepler-11: Folded Light Curves Normalized Flux Time (hr) Time (hr) Lissauer+ 2011

19 Image credit: NASA Ames/Kepler Mission

20 Lissauer+ 2011

21 Composition of Kepler-11 s Planets Image credit: Sam Quinn, Harvard Smithsonian Center for Astrophysics

22 TTVs & Uniqueness Kepler-19b Ford & Holman 2007 Ballard+ 2011

23 Characterizing the Exoplanet Population

24 Sizes of Planet Candidates 1181 Neptune-size Super Earth-size 680 Earth-size 207 Jupiter-size 203 Super 27 Jupiter-size

25 Eccentricities, Inclinations & Multiplicity Three key probes of planet formation: Eccentricity distribution (+ stellar densities) Transit duration distribution Inclination distribution + Frequency of multiple planet systems (+ Period distribution) Frequency of multiply transiting systems Frequency of multiple planet systems + Eccentricity Distribution (+ Period distribution) Distribution of TTV signatures One complex inverse problem!

26 Eccentricities, Inclinations & Multiplicity Three key probes of planet formation: Eccentricity distribution (+ stellar densities) Transit duration distribution Inclination distribution + Frequency of multiple planet systems (+ Period distribution) Frequency of multiply transiting systems Frequency of multiple planet systems + Eccentricity Distribution (+ Period distribution) Distribution of TTV signatures One complex inverse problem! (Observables, Desired Distributions, Both)

27 Modern Statistical and Computational Methods for Analysis of Kepler Data SAMSI June 10-28, 2013 Contacts: Eric Ford (UF), Jim Berger (Duke), Paul Baines (UC Davis), David Hogg (NYU)