ILASOL 2011 Amri Wandel, HUJI SETI in the Kepler era 1 The Impact of Kepler on the Chances to detect Extra-terrestrial Life

ILASOL 2011 A. Wandel Are we alone?  The SETI era: 1960  Searching Extra Terrestrial Intelligence  The exo-planet boom  What has changed with Kepler? 2

ILASOL 2011 A. Wandel How frequent is extra-terrestrial life? 3

ILASOL 2011 A. Wandel How many civilizations exist in our Galaxy ? stars 10% Sunlike Planets in HZ Earthlike n HZ ? ? Kepler 22b Kepler 20e,f

ILASOL 2011 A. Wandel Star types suitable for the evolution of life  Not too big, so that their Main Sequence lifetime will be sufficient for the evolution of life (<1.5Msun)  Not too small – below ~0.5 Msun they are eruptive (planetary temperature instable)  This leaves ~ 10% of all stars. 5

עוברי כוכבים ו ” מערכות שמש ” בערפילית אוריון עוברי כוכבים ו ” מערכות שמש ” בערפילית אוריון Planetary disks in Orion 6 ILASOL 2011 A. Wandel

51 Peg 7 ILASOL 2011 A. Wandel The Doppler method

The transit method The inclination must be very close to 90° 8 ILASOL 2011 A. Wandel

HD HD Planet mass Planet radius Planet density 9 ILASOL 2011 A. Wandel

Observatories in Space SIM Kepler Darwin CoRoT 10 ILASOL 2011 A. Wandel

Sensitivity of exo-planet projects  Radial velocity (Doppler)  Transit  Micro-lensing 11 ILASOL 2011 A. Wandel

The Kepler mission Search Earthlike exo-planets 12 ILASOL 2011 A. Wandel

Exo-Planets by Micro-lensing 13 ILASOL 2011 A. Wandel

Some questions about extra- terrestrial life & intelligence  Is the evolution of life common?  How can we detect life?  How common (or rare) is intelligent life?  How do we define intelligence?  What is the lifetime of a civilization?  Are there many civilizations in the Galaxy or we are the only one?  How can we look for extraterrestrial civilizations? 14

ILASOL 2011 A. Wandel How many civilizations are in the Galaxy ? stars in MW 10% Sunlike ?Planets in HZ ?? Earthlike n HZ Lifetime fbfbfbfb

ILASOL 2011 A. Wandel The Drake parameters R* ~ 10 yr -1 star formation rate in the Galaxy  F s – fraction of stars suitable for life  F p – fraction of stars with planets  Fe – fraction of Earthlike planets  n p - average # of planets in star ’ s HZ  Fb - probability for evolution of biology ?  F i - probability for evol. of intelligence ??  L - average longevity as radio-civilizations ??? 16

ILASOL 2011 A. Wandel How many civilizations NOW? Suppose technological civilizations have an average longevity of L years… then the current number of civilizations is: N = No x L / t(Gal) N = n x F s x F p x n hz x Fb x F i x L/t R* = n/t~100 bil.stars/10 bil.yrs = 10 stars/yr R* = n/t~100 bil.stars/10 bil.yrs = 10 stars/yr is the star formation rate in the Galaxy N= R* x F s x F p x n hz x F b x F i x L 17

ILASOL 2011 A. Wandel The Drake equation N= R* x F s x F p x F E x n hz x F b x F i x L astronomical factors bio-social factors R E - formation rate of habitable Earth-like planets R E = R* x F s x F p x F E x n hz R E = R* x F s x F p x F E x n hz = 10x 0.1 x 1 x 1 x 1= 1 (optimist) = 10x 0.1 x 0.1x0.1x 0.1=0.001(pessimist) = 10x 0.1 x 0.1x0.1x 0.1=0.001(pessimist) N = R E x F b x F i x L N = R E x F b x F i x L 18

ILASOL 2011 A. Wandel The 3 unknown factors 1) Fb – evolution of life (biology) ~1? 2) Fi – evolution of intelligence (civilization with radio technology) <<1? 3) L – average lifetime of communicative (radio) civilization <10,000 yr? Example: Fb=100%, Fi=1% L=10,000 yrs If R E ~1 N~1x0.01x10,000= 100 If R E ~1 N~1x0.01x10,000= 100 Fb x Fi x L 19

ILASOL 2011 A. Wandel Longevity : L We exist less than 100 years as a technological radio-emitting (“communicative”) civilization Civilizations may disappear because of: Self destruction (wars, nuclear weapons) Ecological disaster Astronomical disaster (e.g. asteroid collision) But within less than 1000 yrs they can spread out of their home planet (other planets, space stations) Some civilizations may disappear a short time (<1000 yrs) after they become communicative Some civilizations may disappear a short time (<1000 yrs) after they become communicative Civilizations surviving these “childhood diseases” may exist much longer, but… 20

ILASOL 2011 A. Wandel Narrow window for communication Civilizations might be detectable via radio waves during only a relatively short period (<1000 yrs?) as they could: Upgrade to more efficient, low radiation channels – satellite, fiber optics, laser Use other communication methods, yet unknown to us Self-distruct or decay So one may assume L is ~ years 21

ILASOL 2011 A. Wandel Earthlike planets rare: Earthlike planets rare: N = x Fi x L Fi Fi L

ILASOL 2011 A. Wandel Earthlike planets frequent: Earthlike planets frequent: N = 1 x Fi x L Fi Fi L

ILASOL 2011 A. Wandel Probability for a civilization within 100 ly 24 Log N or Log L/F ic (R E Fb=1)

ILASOL 2011 A. Wandel Distance between civilizations  N civilizations randomly distributed in a flat disc of diameter D  d average distance to nearest civilization  area occupied by one civilization ~ d 2  Area of the Galactic disc ~ D 2  D 2 ~ Nd 2 => d = D/ N 1/2  D~100,000 ly d=100,000/ N 1/2  N = ,000 1,000,000  d = 10,000 1, ly D d 25

ILASOL 2011 A. Wandel SETI – Serch of Extra-Terrestrial Intelligence 26

ILASOL 2011 A. Wandel What do we search? Artificial radio-signals (leakage) of extra-Terrestrial origin Why? We assume other Civilizations use radio waves for communication like we do How? Radio-telescopes- giant dishes and arrays SETI27

ILASOL 2011 A. Wandel Radio-telescope 28

ILASOL 2011 A. Wandel The largest radio-teolescope: Arecibo 300m dish29

ILASOL 2011 A. Wandel How far can we detect leakage radio signals? Arecibo targeted sensitivity – a few ly Future arrays – tens of light years If there are 10,000 civilizations in the Galaxy, the average distance between neighbor civilizations is ~1000 ly The probability that one is within 100 ly from Earth is in that case is ~1% The SETI chanses 30

ILASOL 2011 A. Wandel We don’t even know what are the chances to detect them… We still don’t know if there are extra-terretrial civilizations..31

ILASOL 2011 A. Wandel 32..but after one year of Kepler data, the chances seem much better.