The Ĝ Infrared Search for Extraterrestrial Civilizations With Large Energy Supplies. Ii. Framework, Strategy, and First Result

Wright, Jason T.; Griffith, R. L.; Sigurd̵sson, Steinn; Povich, Matthew S.; Mullan, B.

doi:10.1088/0004-637x/792/1/27

Cited by 99 publications

(83 citation statements)

References 30 publications

(33 reference statements)

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“…Specifically, he noted that large light-blocking structures around a star would obscure the star, making it dimmer in the optical, and reradiate the collected starlight in the thermal infrared (according to its effective temperature). This paper focuses on the former effect, but the latter effects would also be observable with modern astronomical techniques (Wright et al 2014a(Wright et al , 2014b. Arnold (2005) noted that long-term, precise photometric monitoring of stars for transiting exoplanets by Kepler (Borucki et al 2010b) is effectively a search for alien megastructures while searching for transiting planets, because Kepler had the capacity not only to detect such structures but the photometric precision to distinguish many classes of megastructures from exoplanets.…”

Section: Introductionmentioning

confidence: 99%

The Ĝ Search for Extraterrestrial Civilizations With Large Energy Supplies. Iv. The Signatures and Information Content of Transiting Megastructures

Wright

Cartier

Zhao

et al. 2015

ApJ

120

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Arnold, Forgan, and Korpela et al. noted that planet-sized artificial structures could be discovered with Kepler as they transit their host star. We present a general discussion of transiting megastructures, and enumerate 10 potential ways their anomalous silhouettes, orbits, and transmission properties would distinguish them from exoplanets. We also enumerate the natural sources of such signatures. Several anomalous objects, such as KIC 12557548 and CoRoT-29, have variability in depth consistent with Arnold's prediction and/or an asymmetric shape consistent with Forgan's model. Since well-motivated physical models have so far provided natural explanations for these signals, the ETI hypothesis is not warranted for these objects, but they still serve as useful examples of how nonstandard transit signatures might be identified and interpreted in a SETI context. Boyajian et al. recently announced KIC 8462852, an object with a bizarre light curve consistent with a "swarm" of megastructures. We suggest that this is an outstanding SETI target. We develop the normalized information content statistic M to quantify the information content in a signal embedded in a discrete series of bounded measurements, such as variable transit depths, and show that it can be used to distinguish among constant sources, interstellar beacons, and naturally stochastic or artificial, information-rich signals. We apply this formalism to KIC 12557548 and a specific form of beacon suggested by Arnold to illustrate its utility.

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Section: Introductionmentioning

confidence: 99%

The Ĝ Search for Extraterrestrial Civilizations With Large Energy Supplies. Iv. The Signatures and Information Content of Transiting Megastructures

Wright

Cartier

Zhao

et al. 2015

ApJ

120

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“…In a series of papers, Wright et al (2014a) and Wright et al (2014b) have presented a detailed description of our current ability to detect the signature of advanced Kardashev Type III civilisations (Kardashev 1964) via the prominent waste heat signature they are expected to produce. Type III civilisations are defined by Kardashev (1964) as those capable of harnessing the stellar energy supply of a galaxy (∼10 38 Watts).…”

Section: Introductionmentioning

confidence: 99%

“…If the radiation measured by WISE is interpreted as waste heat emission from an advanced civilisation, the source sample includes galaxies Table 1 is available in electronic form at http://www.aanda.org reprocessing more than 25% of their starlight into the mid-IR (i.e. γ > 0.25 in the formalism of Wright et al 2014b). While some of these sources are well known (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…The resulting cleaned catlogue of ∼31 000 extended red objects is therefore biased to include nearby galaxies that are prominent mid-IR sources with extreme colours. In addition, Griffith et al (2015) apply the AGENT methodology (Wright et al 2014b) to identify 93 sources that have mid-IR colours consistent with γ > 0.25 where γ is the fraction of starlight reemitted in the mid-IR as waste heat products, as modelled by the Wright et al (2014b) AGENT analysis of the four WISE observing bands (3.4, 4.6, 12, and 22 microns).…”

Section: Introductionmentioning

confidence: 99%

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Application of the mid-IR radio correlation to the Ĝ sample and the search for advanced extraterrestrial civilisations

Garrett

2015

A&A

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Wright et al. (2014, ApJ, 792, 26) have embarked on a search for advanced Karadashev Type III civilisations via the compilation of a sample of sources with extreme mid-IR emission and colours. The aim is to furnish a list of candidate galaxies that might harbour an advanced Kardashev Type III civilisation; in this scenario, the mid-IR emission is then primarily associated with waste heat energy byproducts. I apply the mid-IR radio correlation to this Glimpsing Heat from Alien Technology (Ĝ) sample, a catalogue of 93 candidate galaxies compiled by Griffith et al. (2015, ApJS, 217, 25). I demonstrate that the mid-IR and radio luminosities are correlated for the sample, determining a k-corrected value of q 22 = 1.35 ± 0.42. By comparison, a similar measurement for 124 galaxies drawn from the First Look Survey (FLS) has q 22 = 0.87 ± 0.27. The statistically significant difference of the mean value of q 22 for these two samples, taken together with their more comparable far-IR properties, suggests that theĜ sample shows excessive emission in the mid-IR. The fact that theĜ sample largely follows the mid-IR radio correlation strongly suggests that the vast majority of these sources are associated with galaxies in which natural astrophysical processes are dominant. This simple application of the mid-IR radio correlation can substantially reduce the number of false positives in theĜ catalogue since galaxies occupied by advanced Kardashev Type III civilisations would be expected to exhibit very high values of q. I identify nine outliers in the sample with q 22 > 2 of which at least three have properties that are relatively well explained via standard astrophysical interpretations e.g. dust emission associated with nascent star formation and/or nuclear activity from a heavily obscured AGN. The other outliers have not been studied in any great detail, and are deserving of further observation. I also note that the comparison of resolved mid-IR and radio images of galaxies on sub-galactic (kpc) scales can also be useful in identifying and recognising artificial mid-IR emission from less advanced intermediate Type II/III civilisations. Nevertheless, from the bulk properties of theĜ sample, I conclude that Kardashev Type III civilisations are either very rare or do not exist in the local Universe.

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“…Dyson 1960;1966;Freitas Jr and Valdes 1985;Beech 2008;Bradbury, Ćirković, and Dvorsky 2011;Wright et al 2014;Vidal 2014a, chap. 9).…”

Section: -Why Extraterrestrials Will Not Communicatementioning

confidence: 99%

A multidimensional impact model for the discovery of extraterrestrial life

Vidal¹

2015

The Impact of Discovering Life Beyond Earth

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Abstract:I first argue that the extraterrestrials we will find will not communicate, for the simple reason that they would likely be either immensely inferior or immensely superior to us. Then, I argue that the discovery of extraterrestrials will be slow, like other previous major scientific discoveries. I introduce a multidimensional model to assess and to prepare the impact of discovering extraterrestrial life. Twenty-six dimensions are introduced, illustrated with spider diagrams, which cover both what extraterrestrial might look like, and how humans may react.

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The Ĝ Infrared Search for Extraterrestrial Civilizations With Large Energy Supplies. Ii. Framework, Strategy, and First Result

Cited by 99 publications

References 30 publications

The Ĝ Search for Extraterrestrial Civilizations With Large Energy Supplies. Iv. The Signatures and Information Content of Transiting Megastructures

The Ĝ Search for Extraterrestrial Civilizations With Large Energy Supplies. Iv. The Signatures and Information Content of Transiting Megastructures

Application of the mid-IR radio correlation to the Ĝ sample and the search for advanced extraterrestrial civilisations

A multidimensional impact model for the discovery of extraterrestrial life

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