searching for extraterrestrial intelligence beyond …ez/talks/seti13.pdfthe kardashev scale...
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Searching for Extraterrestrial Intelligence Beyond the Milky Way
The first Swedish SETI project
Erik ZackrissonDepartment of Astronomy
Oskar Klein Centre
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Searching for ExtraterrestrialIntelligence (SETI) – A Brief History I
• 1959 – Cocconi & Morrison (Nature): ”Try the hydrogen frequency (1.42 GHz)”
• 1960 – Project Ozma
• 1961 – Schwartz & Townes(Nature): ”Try optical laser”
• 1977 – The Wow signal
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Searching for ExtraterrestrialIntelligence (SETI) – A Brief History II
• 1984 – The SETI Institute
• Late 1990s – Optical SETI becomes popular
• 1999 – SETI@home
• 2007 – Allen Telescope Array
• 2012 – SETI Live
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The Fermi Paradox
• No signals from E.T. despite 50 years of SETI
• The Milky Way can be colonized in 1% of itscurrent age – why are wenot already colonized?
• Where is everybody?
50+ possible solutions are known (e.g. Brin 1983, Webb 2002)
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A Few Possible Explanations
• Everybody is staying at home and nobody is transmitting– Virtual worlds more exciting than
space exploration?– Berserkers Transmission = Doom
• Wrong search strategy– Try artefacts, Bracewell probes,
IR laser, internet, DNA, Dyson spheres…
• Intelligent life is extremely rare– Try extragalactic SETI
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Beyond the Milky Way
• Carl Sagan: ”More stars in the Universe thangrains of sand on all the beaches on Earth”
• Stars in Milky Way 1011
• Stars in observableUniverse 1023
Only a handful of extragalactic SETI projectscarried out so far!
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Earth-like planets in a cosmological context I
Erik Zackrisson, Anders Johansen, Juan González (2014, in prep.)
Millenium simulation +Semi-analytic galaxy models + Metallicity-dependent planet formationThe typical Earth-like planet in the local Universe is 3 Gyr older than Earth!
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Earth-like planets in a cosmological context II
Earth-like planets aroundSolar-type stars in the observable Universe: 1018
Comparable to grains ofsand on the longest beach in Sweden!
Laholmsbuktens strand –the longest beach in Sweden (12 km)
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Supercivilizations –The Kardashev scale
• Based on the amountof energy that acivilization is able to harness
• Kardashev (1964): Type I, II & III
Nicolai Kardashev
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Kardashev type I, II, III
Similar to the Solar insolation on Earth(1017 W)
Power consumption:
Similar to the luminosityof their parent star(1026 W for the Sun)
Similar to the luminosityof their home galaxy(1037 W for the Milky Way)
Type I
Type II
Type III
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The Dyson Sphere
Freeman DysonDimensions envisioned for a Solar system Dyson sphere made by disassembled planets
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Dyson ring Dyson swarm Dyson bubble
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Hunting for Kardashev type III
The Tully-Fisher relation
Lum
ino
sity
HI line width (mass)
Galactic-scale colonizationusing Dyson sphereMass unaffected butdiminished UV/opticalluminosity
Very few disk galaxiesdeviate from the Tully-Fisher relation Kardashev type IIIsmust be rare (Annis 1999)
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The largestsextragalactic SETI project so far!
Per Calissendorff (2013, BSc thesis, SU)Erik Zackrisson, Per Calissendorff, Saghar Asadi (2014, in prep.)
Lum
ino
sity
HI line width (mass)
5000 disk galaxies
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But what are the outliers?
Example I: Edge-on disk incorrectly assigned a lower inclination
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But what are the outliers?
Example II: Two interacting (?) disks incorrectly classified as one object
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Per Calissendorff (2013)
Colonization using Dyson spheres
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Per Calissendorff (2013)
Colonization using Dyson spheres
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Per Calissendorff (2013)
Colonization using Dyson spheres
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Per Calissendorff (2013)
Colonization using Dyson spheres
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Per Calissendorff (2013)
Colonization using Dyson spheres
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Per Calissendorff (2013)
Colonization using Dyson spheres
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Per Calissendorff (2013)
Colonization using Dyson spheres
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Per Calissendorff (2013)
Colonization using Dyson spheres
![Page 25: Searching for Extraterrestrial Intelligence Beyond …ez/talks/SETI13.pdfThe Kardashev scale •Based on the amount of energy that a civilization is able to harness •Kardashev (1964):](https://reader035.vdocuments.site/reader035/viewer/2022071110/5fe4eb0f926bca633f6cf950/html5/thumbnails/25.jpg)
Per Calissendorff (2013)
Colonization using Dyson spheres
![Page 26: Searching for Extraterrestrial Intelligence Beyond …ez/talks/SETI13.pdfThe Kardashev scale •Based on the amount of energy that a civilization is able to harness •Kardashev (1964):](https://reader035.vdocuments.site/reader035/viewer/2022071110/5fe4eb0f926bca633f6cf950/html5/thumbnails/26.jpg)
Per Calissendorff (2013)
Colonization using Dyson spheres
![Page 27: Searching for Extraterrestrial Intelligence Beyond …ez/talks/SETI13.pdfThe Kardashev scale •Based on the amount of energy that a civilization is able to harness •Kardashev (1964):](https://reader035.vdocuments.site/reader035/viewer/2022071110/5fe4eb0f926bca633f6cf950/html5/thumbnails/27.jpg)
Per Calissendorff (2013)
Colonization using Dyson spheres
![Page 28: Searching for Extraterrestrial Intelligence Beyond …ez/talks/SETI13.pdfThe Kardashev scale •Based on the amount of energy that a civilization is able to harness •Kardashev (1964):](https://reader035.vdocuments.site/reader035/viewer/2022071110/5fe4eb0f926bca633f6cf950/html5/thumbnails/28.jpg)
Per Calissendorff (2013)
Colonization using Dyson spheres
![Page 29: Searching for Extraterrestrial Intelligence Beyond …ez/talks/SETI13.pdfThe Kardashev scale •Based on the amount of energy that a civilization is able to harness •Kardashev (1964):](https://reader035.vdocuments.site/reader035/viewer/2022071110/5fe4eb0f926bca633f6cf950/html5/thumbnails/29.jpg)
Complications
• Colonization using Dyson spheres
– Modified surface brightness profile
– Misinterpreted axial ratios
• Object not classified as disk galaxy and never entersTully-Fisher sample?
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Summary• Largest extragalactic Dysonian SETI project yet
• Star-fed Kardashev type III civilizationsextremely rare in disk galaxies (<0.5%)
• Some KIII candidates are clearly due to failedmeasurements or misclassifications
• What are the others? We don’t know yet…