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How to Find Life on Other Planets?

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Thermodynamic exo-civilization markers: What it takes to find them in a census of the solar neighborhood Jeff Kuhn (Svetlana Berdyugina...Dave Halliday, Caisey Harlingten) Fermi (1950): “Where is everyone?” A timescale problem Life on the Earth is 3.8Gyrs old Within 100,000 lt-yr there are about 100 billion stars In cosmic terms, the Sun is neither particularly old, nor young…. So, If any civilizations live for thousands or millions of years, why don’t we see evidence of them? “We’re not special” SETI Programs: Making the Fermi paradox an astrophysical problem Search for intentional or beaconed alien signals . Radio communication . Optical communication Power leakage classification (Kardashev 1964): . Type I: planet-scale energy use . Type II: star-scale energy use . Type III: galaxy-scale energy use But these are heavily based on assumptions about alien sociology... Unintentional signals: . Dyson (1960): thermal signature of star-enclosing biosphere . Carrigan (2009): IR survey, Type II and III, no candidates Seeing Extra-Terrestrial Civilizations, Timeline: (“We’re not special”) time ETC ETC becomes “emerges” “hot” and Earth’s detection thermodynamically technology developed visible Fraction of Number ETCs Fraction with Fraction that “Successful” Detectible Planets develop Civilization civilizations N = N f n f f f DSCS P HZ BE Number Stars Number planets Fraction that warm In detection in Habitable Zone Before Earth radius Suppose we could detect ETCs… • NS -- 600 stars bright enough (with mV < 13) within 60 light years • fP – about 50% have planets • nHZ – about 0.5 habitable zone planets per extrasolar system • fC – we’re not special, say 50% develop civilizations sometime • fBE – we’re not special, say 50% are more advanced than Earth • fS – the probability that civilization “survives” ND = 38 x fS or 7% of NS x fS The likelihood that civilization is long-lived is something we can (potentially!) learn from astronomical observations… Power Consumption Type I’s evolve toward greater power consumption . power consumption correlates w. information, doubles over 3yr . power consumption increases faster than population Parametrization: Ω(t)=P(t)/Pstar, 10-7 10-6 10-5 10-4 0.001 0.01 0.1 1 Roman period Present human Present Photosynthetic Global solar global power biological heat global power global power power production production production consumption absorption Present global optical power production Global Warming Type I Civilization Heat Islands Biological and technological activities produce unavoidable heat Detroit Chicago +10C Columbus St.Louis Type I Signature Planet with ΩE < Ω < 1 . Planet is “too warm” not this one compared to its stellar heat budget . Heat is geographically distributed (activity areas) . Heat islands are not “too hot” (not geothermal) . Reduced albedo due to photonic power usage ETC Type I: planet with IR/Vis brightness ratio Darya Rios An experiment: Scale Earth data for exocivilization IR/Vis simulation Earth: NASA Earth Observations (NEO) database . Temperature & Albedo maps multiwavelength photometry Model Input Temperature/day . 12 month data . day/night . visual, 5 µm, 10 µm . Integrated 1x1 . planet rotation: Prot = 10 d . orbital motion: Porb = 100 d Man-made lights/night Albedo Earth’s Visual Brightness Signal Visible brightness is dominated by scattered sunlight Visual Reflectance/day 106 Man-made lights/night IR Brightness IR variability is due primarily to land-water geography Flux residuals: F(5 µm)~0.8%, F(10 µm)~0.5% Visual Reflectance/day Ω > 0.01 can be detected 103 10 µm x2 5 µm Civilization Biomarkers: Albedo analysis 12% 0.6% 2% 0.5% Ω ~ 0.01 x50 of the current human civilization scaled from man- made light signal F(10µm) signal with F(5µm) as reflectance reference Total F Recoverd F Type I ETC can be detected even when natural stellar heating dominates the total planetary flux Seeing civilization through the natural exoplanet surface variability • Albedo variations account for most of the variability at any wavelength • Albedo can be measured at short wavelengths then used to remove “non-civilization” IR variability • Simple models have sensitivity to detect Earth- like civilizations with Ω > 0.01 (Ωearth≈ 0.0005) • More complex models using rotational inversions using visible, 5 and 10μ light have greater (TBD) potential Detection complexities Clouds: . Complete cloud cover no detection possible . Partial clouds longer series of observations Geothermal activity: . multicolor observations to estimate temperature of the sources & to disregard “too hot” spots Other false-positives: . Additional, spectroscopic biomarkers Spectroscopic Life Signatures Spectroscopy: . Water (H2O) O 2 H2O . Ozone (O3) . Methane (CH4) . Nitrous oxide (N2O) . Photosynthetic molecules . Non-equilibrium gases! Photosynthetic clear ocean 100% molecules: • Chlorophil • Carotenoids • Anthocyanins • Phycobilin Nearly 2000 exoplanets, ≈20 Habitable zone (liquid water) candidates 7000K 4000K How many planets? Kepler mission estimate: there are 17 billion other Earths in the Milky Way. ... known detectable super-Earths in HZs d < 20 pc, Vmag < 13 Planet M/M R/R Stellar d [pc] Ang. sep. V Ref. Sp. [mas] [mag] Gliese 163 c >7.2 - M3.5V 15.0 8.4 11.8 6 HD40307 g >7.1 - K2.5V 12.8 47 7.2 7 HD85512 b >3.5 - K5V 11.2 23 7.7 2 Gliese 667C c >4.3 - M1.5V 6.8 18 10.2 3,4,5 Gliese 832 c >5.0 - M1.5V 4.9 33 8.7 1 Kapteyn b >4.8- - dM1 3.9 43 8.8 8 α Cen A HZ - - G2V 1.3 944 0.0 9 α Cen B HZ - - K1V 1.3 558 1.3 9 α Cen C HZ - dM5e 1.3 38 11.1 9 Detectable HZ Earths & ETCs HZ Earths ETC Ω ~ 1 2REarth 5REarth WLT’s: The Keck mirror and its PSF Mirror Phase Errors A star looks like this with And like this when we good AO… remove the star… (Circular avg. removed) (this is not the PSF we need for planet or ETC detection) The EELT M1 geometry… Next Generation Telescopes Requirements to detect life and ETC on nearby Earths . high level of scattered light suppression in order to see the faint terrestrial planet against the optical “glare” of the nearby star adaptive optics and coronograph, contrast 10–8 . sufficient sensitivity for detecting enough photons from the planet to allow statistical analysis of its variability large aperture . low-enough thermal emissivity so that the planetary IR flux is not lost in the terrestrial thermal background low IR emissivity Worlds Largest Telescopes (WLT) GMT EELT Keck TMT OWL Scaling telescopes OWL EELT TMT GMT Keck M α D2 HET * (fixed gravity) Currently planned WLTs are technologies extrapolated from Keck – we can break this curve only by changing basic WLT telescope assumptions Colossus Consortium. Waterton CA, Sept. 2012 Harlingten Optics, CA IfA Dynamic Structures, CA Tohoku, Japan KIS, Germany NASA Ames (advisor) Benson Glass MDM, CA Univ. Lyon, France UCSD UNAM, Mexico Astronomy Magazine Colossus Optical Configuration 60 x 8m phased-array telescopes M1: 60 x 8 OAP M1 - R=40m parabola Image F/ 5 f = 380m M2: 60 x 3.5cm M2 M1 Y X Z 3D Layout Colosus 0.1, 74m diameter 5/21/2014 col3.ZMX 74m 3.6m Configuration 1 of 6 λ wavelength, at 0.5 > S ratio: Strehl of 500nm of FOV: 8 mas 8 FOV: 1.0000 OBJ: 0.0000, 0.0000 (deg) OBJ: 0.0006, 0.0000 (deg) 100.00 2” FOV 2” - +/ OBJ: 0.0000, 0.0006 (deg) IMA: 0.000, 0.000 M IMA: -0.005, 0.000 M OBJ: -0.0006, 0.0000 (deg) OBJ: 0.0000, -0.0006 (deg) IMA: 0.000, -0.005 M Strehl IMA: 0.005, 0.000 M IMA: 0.000, 0.005 M Surface: IMA Spot Diagram Colosus 0.1, 74m diameter 8/27/2012 Units are µm.Airy Radius : 7.717 µm Field : 1 2 3 4 5 RMS radius : 0.406 7.860 7.860 7.860 7.860 GEO radius : 0.590 20.138 18.229 20.138 18.229 col2.ZMX Scale bar : 100 Reference : Chief Ray Configuration 1 of 6 Colossus Telescope Colossus Encoding mirror phase in the psf One mirror phase change p/2 0.01 arcsec Coronagraphy at 10-7 10-8 contrast Subaru, SCExAO team: Guyon, Martinache, et al (2014) Image domain mirror phase recovery PSF from 59 random mirror phases 8m Airy 8 diffraction ring Slumped 6mm plate glass, parabolicity Parabolic deviation, 100μm rms 0.5m diameter, 2m curvature radius parabola Thin mirrors, actuators and gravity deformation a D 4 2 zpp = 10ρa /Et a, t in cm, E in Pa, rho cgs Borosilicate… M=100g t=1cm with a=10cm Z = 25nm, a=20cm, t=5cm D=8m 5000 actuators Area mass density 500kg/m^2 60kg/m^2 www.the-colossus.com 60 independent off-axis 8m telescopes merging telescope-interferometry concepts to achieve 74m diameter effective resolution, ‘almost filled’ The secondary structure is less than 5m in diameter With 60 independent <0.5m optics Each 8m segment is a diff-limited 8m telescope, using AO with deformable M2 segment subaper.s The primary consists of 60x8m off-axis parabolic primaries WLT scaling law and Colossus OWL EELT TMT GMT Col * Keck Summary ETC global warming is a detectible ETC marker Planned telescopes are too small and not good for scattered light Colossus Telescope could detect 10’s of ETC’s in the solar neighborhood within 60 light years of the Earth www.the-colossus.com To learn more (or be involved): www.the-colossus.com (Astrobiology Jour, SPIE, TEDx...).
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