Kepler’s Exoplanet Discoveries:Implications for the Prevalence of Extra-Terrestrial Intelligence Robert McCann, Ph.D. NASA Ames Research Center Special Acknowledgments: Dr. Natalie Batalha 1 Dr. Bill Borucki
Milky Way Galaxy• Large Barred Spiral• 90K LY in Diameter• ~200B stars• ~20B FGK’s • <1995 CE: • 1 Planetary System • 1 Intelligent life form capable of putting together a ppt presentation
• Kepler Mission • Primary Goal: Detect Earth-sized planets in HZ of their star • Quantify how plentiful they are• Giant (95 MP) photometer in space • 167K sun-like stars in FOV• Launched March 2009 • 156K selected for monitoring• First Light: May 2009
Implications for ETI Drake Equation1961: • Frank Drake develops Drake Equation • Equation to calculate the number of civilizations in our galaxy that we could potentially receive a signal from.N = R* x fPlanet x ne x fLife x fIntelligence x fCivilizations x LN = the number of transmitting/communicating civilizationsR* = galactic birthrate of G/K/M type stars suitable for hosting life (~10/year)fPlanet = the fraction of such stars having planetsne = the number of those planets that are habitablefLife = fraction of those planets on which life originated/evolvedfIntelligence = the fraction of inhabited worlds that developed intelligent lifefCivilizations = the fraction of inhabited worlds that developed civilizations capable of interstellar communicationL = lifetime of those communicating civilizations•Kepler: Fraction of sun-like (FGK) stars with a habitable planet • Consolidation of terms fPlanet and ne
Kepler Modus Operandi: Transit Method Kepler-16 (2) Kepler-10 Kepler-15 Kepler-4 HAT-p-11 Kepler-6 Kepler-22 TrES-2 Kepler-14 Kepler-17 KOI-428HAT-p-7 Kepler-13 KOI-423 Kepler-8 Kepler-5 Kepler-12 Kepler-7 Kepler-11 line-of-sight: Rs/Rorbit• Proportion of planets in(6) Kepler-21 Kepler-18 (3)• For Earth-sized planets in Earth-sized orbits: Kepler-19 Kepler-9 (3) • .005 (1/200) (2) • If all 156K stars in Kepler FOV contain an Lissauer et al. 2011, Nature, 470, 53 earth-analog: • Kepler would detect 780 of them 5
HZ Candidates 48 with Teq between 185 and 303 K (Earth = 255 K) Jun 2010 Feb 2011 Dec 2011Size Relative to Earth Equilibrium Temperature [K] 12
HZ Candidates Ten with Rp < 2 Re (185 K < Teq < 303 K) Jun 2010 Feb 2011 Dec 2011Size Relative to Earth Equilibrium Temperature [K] 13
Only a matter of time before discovery of “ηEarths” • 0 .95 AU < a < 1.37 AU (Kasting et al., 1993) • 0.8REarth < r < 2REarth• Q0-Q6: May 2009 - Sep 2010• As of May 2012: Will Double observation time from 18 to 36 months• 3 transits of ηEarth’s obtained 14
When will we know? ?• Lower S/N ratio than originally designed for • More transits required 15 Nature 477, 142-143 (Sept 6, 2011)
Stellar Noise: simulation vs observation 6.5-hr variability is stochastic and will average out over multiple orbits The goal of true Earth-analogs is 1.2-Re, P=365 d 1.0-Re, P=365 d reachable by extending the mission length Jenkins et al.: Poster 19.14 1.0-Re, P=225 d 30 ppm 20-ppm 1.0-Re, P=365 d 16
Extrapolation based on Existing Kepler Data Feb 2011• Catanzarite and Shao (2011): • Defined Earth Analog Planets (ηEarth): • .95 AU < a < 1.37 AU (Kasting et al., 1993) • .8REarth < r < 2REarth • How many should Kepler find? ? 17
Q0-Q5: May 2009 - Jun 2010 Size Relative to Earth Orbital Period in days 18• Planets cluster between orbital periods of 3 and 40 days • Mathematical extrapolation: Occurrence rate of ηEarth around sun-like stars is 1.1- 0.3 % +0.6 • If exactly 1.1%, Kepler should detect 9 ηEarths
Dec 2011“The new (2012) Keplerdata set shows that thecompleteness of theFebruary 2011 data set wasover-estimated. Size Relative to EarthFor planets over twice thesize of Earth with orbitalperiods shorter than 40days, detections wereexpected to be 100%complete, so that no moreplanets remained to befound in the new 2012 dataset.” Orbital Period in days “The surprise is that a substantial number of planets with sizes and periods in that range were in fact found in the 2012 data release. 19 At this point we can only say that the revised estimate will likely be higher than the number given in our paper.” - Joseph Catanzarite, Personal Communication, March 2012
Extrapolations1.1 + 0.6 = 1.7% = 13 ηEarths• 13*200 = 2604 ηEarths in Kepler’s sample of 153,196 FGK stars • 20 Billion FGK’s in Milky Way• ~340 million η Earths in our Milky Way Alone! 20
Implications The Drake Equation Fermi ParadoxL N = R* x fPlanet x ne x fLife x f x f Intelligence x Civilizations If ne = 1.7% (340 million ηEarths)• Expect to have a large number of civilizations. It is only a matter of time before they develop the ability for intergalactic travel.If:-you could travel at 10% the speed of light, 0.1 c (3 x 107 m/sec) Enrico FermiAnd:The average distance between stars is 5 light years (50 years)And:After 150 years you can spread to the next system, sending newcraft to one or two other systems.Then:You could colonize the entire galaxy in 10 million yearsIf you travel at 0.01 c, and it takes 5,000 years between hopsit would only take 100 million years to colonize the entire galaxy.So: Where is Everybody (Fermi Paradox)?
Machine IntelligenceParadox• In 1981, Frank Tipler used the idea of colonization byself-replicating Von Neumann machines to argue that machineswould spread throughout the galaxy as soon as any civilizationreaches a level to build these machines.• Because it doesn’t take much more technological capability than what we already have.• If civilizations are common: • The universe should be overrun by self-replicating machines.
Implications The Drake Equation Fermi ParadoxN = R* x fPlanet x ne x fLife x fIntelligence x fCivilizations x LfLife = fraction of those planets on which life originated/evolvedfIntelligence = the fraction of inhabited worlds that developed intelligent lifefCivilizations = the fraction of inhabited worlds that developed civilizations capable of interstellar communicationL = lifetime of those communicating civilizationsAnswer to Paradox:One or more of these terms must be close to zero- Microbial life should be widespread in the universe- Complex life such as plants and animal will be extremely rare- Earth is “lucky”- Complex Earth life is the result of an extraordinary set of conditions and random chance events- Microbial life appeared quickly; complex life recently- Earth is also special: -in the habitable zone -life-friendly atmosphere -Jupiter and the Moon beneficial -placid part of the galaxy
The Drake Equation ConclusionWe are not alone.But we are very lonely.