Search For Extraterrestrial Intelligence Research Articles

Searching the SETI Ellipsoid with Gaia

The search for extraterrestrial intelligence (SETI) Ellipsoid is a geometric method for prioritizing technosignature observations based on the strategy of receiving signals synchronized to conspicuous astronomical events. Precise distances to nearby stars from Gaia makes constraining Ellipsoid crossing times possible. Here we explore the utility of using the Gaia Catalog of Nearby Stars to select targets on the SN 1987A SETI Ellipsoid, as well as the Ellipsoids defined by 278 classical novae. Less than 8% of stars within the 100 pc sample are inside the SN 1987A SETI Ellipsoid, meaning the vast majority of nearby stars are still viable targets for monitoring over time. We find an average of 734 stars per year within the 100 pc volume will intersect the Ellipsoid from SN 1987A, with ∼10% of those having distance uncertainties from Gaia better than 0.1 lyr.

Earth through the looking glass: how frequently are we detected by other civilizations through photometric microlensing?

ABSTRACT Microlensing is proving to be one of the best techniques to detect distant, low-mass planets around the most common stars in the Galaxy. In principle, Earth’s microlensing signal could offer the chance for other technological civilizations to find the Earth across Galactic distances. We consider the photometric microlensing signal of Earth to other potential technological civilizations and dub the regions of our Galaxy from which Earth’s photometric microlensing signal is most readily observable as the ‘Earth microlensing zone’ (EMZ). The EMZ can be thought of as the microlensing analogue of the Earth Transit Zone (ETZ) from where observers see Earth transit the Sun. Just as for the ETZ, the EMZ could represent a game-theoretic Schelling point for targeted searches for extra-terrestrial intelligence (SETI). To compute the EMZ, we use the Gaia DR2 catalogue with magnitude G < 20 to generate Earth microlensing probability and detection rate maps to other observers. While our Solar system is a multiplanet system, we show that Earth’s photometric microlensing signature is almost always well approximated by a binary lens assumption. We then show that the Earth is in fact well hidden to observers with technology comparable to our own. Specifically, even if observers are located around every Gaia DR2 star with G < 20, we expect photometric microlensing signatures from the Earth to be observable on average only tens per year by any of them. In addition, the EMZs overlap with the ETZ near the Galactic Centres which could be the main areas for future SETI searches.

Searching for Broadband Pulsed Beacons from 1883 Stars Using Neural Networks

The search for extraterrestrial intelligence at radio frequencies has largely been focused on continuous-wave narrowband signals. We demonstrate that broadband pulsed beacons are energetically efficient compared to narrowband beacons over longer operational timescales. Here, we report the first extensive survey searching for such broadband pulsed beacons toward 1883 stars as a part of the Breakthrough Listen’s search for advanced intelligent life. We conducted 233 hr of deep observations across 4–8 GHz using the Robert C. Byrd Green Bank Telescope and searched for three different classes of signals with artificial (or negative) dispersion. We report a detailed search—leveraging a convolutional neural network classifier on high-performance GPUs—deployed for the very first time in a large-scale search for signals from extraterrestrial intelligence. Due to the absence of any signal-of-interest from our survey, we place a constraint on the existence of broadband pulsed beacons in our solar neighborhood: ≲1 in 1000 stars have transmitter power densities ≳105 W Hz−1 repeating ≤500 s at these frequencies.

Mathematical encoding within multiresonant planetary systems as SETI beacons

ABSTRACT How might an advanced alien civilization manipulate the orbits within a planetary system to create a durable signpost that communicates its existence? While it is still debated whether such a purposeful advertisement would be prudent and wise, we propose that mean-motion resonances between neighbouring planets – with orbital periods that form integer ratios – could in principle be used to encode simple sequences that one would not expect to form in nature. In this letter, we build four multiresonant planetary systems and test their long-term orbital stability. The four systems each contain six or seven planets and consist of (i) consecutive integers from 1 to 6; (ii) prime numbers from 2 to 11; (iii) the Fibonacci sequence from 1 to 13; and (iv) the Lazy Caterer sequence from 1 to 16. We built each system using N-body simulations with artificial migration forces. We evaluated the stability of each system over the full 10 Gyr integration of the Sun’s main-sequence phase. We then tested the stability of these systems for an additional 10 Gyr, during and after post-main-sequence evolution of the central stars (assumed to be Sun-like) to their final, white dwarf phase. The only system that was destabilized was the consecutive integer sequence (system i). The other three sequences therefore represent potential Search for Extraterrestrial Intelligence (SETI) beacons.

Afterword: Some Illustrations

Afterword: Some Illustrations

Setigen: Simulating Radio Technosignatures for the Search for Extraterrestrial Intelligence

The goal of the search for extraterrestrial intelligence (SETI) is the detection of nonhuman technosignatures, such as technology-produced emission in radio observations. While many have speculated about the character of such technosignatures, radio SETI fundamentally involves searching for signals that not only have never been detected, but also have a vast range of potential morphologies. Given that we have not yet detected a radio SETI signal, we must make assumptions about their form to develop search algorithms. The lack of positive detections also makes it difficult to test these algorithms’ inherent efficacy. To address these challenges, we present setigen, a Python-based, open-source library for heuristic-based signal synthesis and injection for both spectrograms (dynamic spectra) and raw voltage data. setigen facilitates the production of synthetic radio observations, interfaces with standard data products used extensively by the Breakthrough Listen project, and focuses on providing a physically motivated synthesis framework compatible with real observational data and associated search methods. We discuss the core routines of setigen and present existing and future use cases in the development and evaluation of SETI search algorithms.

Life beyond Earth: How will it first be detected?

An overview of the status and prospects of the search for life in the universe is presented. The search for life beyond the Earth is being carried out using a variety of techniques in three distinct realms of space. First is the study of habitable locations in the Solar System using spacecraft and robotic probes. Second is the detection of the global alteration of exoplanet atmospheres by metabolic processes of microbes, with targets typically Earth-like terrestrial planets within 20 or 30 parsecs. Third is a search for the signatures of technology from extraterrestrial civilizations, in the form of pulsed radio and optical signals, thermal footprints, or physical artifacts. Targets for this third search span a significant fraction of the galaxy. Rough estimates are made of the odds that each of these strategies will be successful and the timescale for that outcome. All the estimates assume that life will form given suitable conditions and chemical ingredients. The best near-term prospect for the detection of life is the detection of biomarkers in exoplanet atmospheres using the James Webb Space Telescope and a set of large, ground-based telescopes that will come online later this decade. Optimal chances of detection center on super-Earths orbiting red dwarf stars. The next best prospect will come from the search for relic traces of life in ancient Mars rocks returned to the Earth, early next decade. Subsequently, missions to several potentially habitable locations in the outer Solar System could detect biomarkers. The most exciting of these involves Titan, where biology would likely have a different biochemical basis than life on Earth. The strategy deemed least likely to succeed, having indeterminate odds of success, is the search for extraterrestrial intelligence, SETI, or more accurately referred to as the search for extraterrestrial technology. The technical capabilities to detect artificial radio and optical pulses has been increasing exponentially, but the parameter space of the search is enormous, and is it impossible to interpret the meaning of a null result. While SETI could succeed at any time, it's likely that life will first be detected on a relatively nearby exoplanet, using spectroscopic methods allied to high resolution imaging. The discovery, when it comes, will be one of the most important in scientific history.

A Beacon in the Galaxy: Updated Arecibo Message for Potential FAST and SETI Projects

An updated, binary-coded message has been developed for transmission to extraterrestrial intelligences in the Milky Way galaxy. The proposed message includes basic mathematical and physical concepts to establish a universal means of communication followed by information on the biochemical composition of life on Earth, the Solar System’s time-stamped position in the Milky Way relative to known globular clusters, as well as digitized depictions of the Solar System, and Earth’s surface. The message concludes with digitized images of the human form, along with an invitation for any receiving intelligences to respond. Calculation of the optimal timing during a given calendar year is specified for potential future transmission from both the Five-hundred-meter Aperture Spherical radio Telescope in China and the SETI Institute’s Allen Telescope Array in northern California to a selected region of the Milky Way which has been proposed as the most likely location for life to have developed. These powerful new beacons, the successors to the Arecibo radio telescope which transmitted the 1974 message upon which this expanded communication is in part based, can carry forward Arecibo’s legacy into the 21st century with this equally well-constructed communication from Earth’s technological civilization.

Intelligence as a planetary scale process

AbstractConventionally, intelligence is seen as a property of individuals. However, it is also known to be a property of collectives. Here, we broaden the idea of intelligence as a collective property and extend it to the planetary scale. We consider the ways in which the appearance of technological intelligence may represent a kind of planetary scale transition, and thus might be seen not as something which happens on a planet but to a planet, much as some models propose the origin of life itself was a planetary phenomenon. Our approach follows the recognition among researchers that the correct scale to understand key aspects of life and its evolution is planetary, as opposed to the more traditional focus on individual species. We explore ways in which the concept may prove useful for three distinct domains: Earth Systems and Exoplanet studies; Anthropocene and Sustainability studies; and the study of Technosignatures and the Search for Extraterrestrial Intelligence (SETI). We argue that explorations of planetary intelligence, defined as the acquisition and application of collective knowledge operating at a planetary scale and integrated into the function of coupled planetary systems, can prove a useful framework for understanding possible paths of the long-term evolution of inhabited planets including future trajectories for life on Earth and predicting features of intelligentially steered planetary evolution on other worlds.

The technosignature researcher on the lookout for exo-civilizations

Meet Sofia Sheikh, one of a handful of postdoctoral researchers who have specialized in the search for extraterrestrial intelligence. She talks to David Appell about strange signals, Star Trek, picking a tricky research field and the importance of mentorship.

One of Everything: The Breakthrough Listen Exotica Catalog

Abstract We present Breakthrough Listen’s Exotica Catalog as the centerpiece of our efforts to expand the diversity of targets surveyed in the Search for Extraterrestrial Intelligence (SETI). As motivation, we introduce the concept of survey breadth, the diversity of objects observed during a program. Several reasons for pursuing a broad program are given, including increasing the chance of a positive result in SETI, commensal astrophysics, and characterizing systematics. The Exotica Catalog is a 963 entry collection of 816 distinct targets intended to include “one of everything” in astronomy. It contains four samples: the Prototype sample, with an archetype of every known major type of nontransient celestial object; the Superlative sample of objects, with the most extreme properties; the Anomaly sample of enigmatic targets that are in some way unexplained; and the Control sample, with sources not expected to produce positive results. As far as we are aware, this is the first object list in recent times with the purpose of spanning the breadth of astrophysics. We share it with the community in hopes that it can guide treasury surveys and as a general reference work. Accompanying the catalog is an extensive discussion of the classification of objects and a new classification system for anomalies. Extensive notes on the objects in the catalog are available online. We discuss how we intend to proceed with observations in the catalog, contrast it with our extant Exotica efforts, and suggest how similar tactics may be applied to other programs.

The Philosophical Aspects of the Dialogue between Modern Cosmology and Theology

Introduction. The paper deals with the philosophical problems of the modern dialogue between cosmology and theology. It is argued that no existential contradiction is possible between them as originating in one and the same human condition. The difference between cosmology and theology amounts to the difference in their open-ended hermeneutics of the outer world. It is from within this philosophical conclusion that the hot issue of the dialogue are discussed and some insights are proposed.Methodology and sources. The philosophical analysis is based on the discussion of epistemological issues in modern cosmology and their relevance to theological view of the world. The method is similar to existential phenomenology’s approach to the constitution of the notion of the universe in cosmology and theology as an open-ended hermeneutics of the world.Results and discussion. It is shown that no existential contradiction is possible between two types of hermeneutics as originating in one and the same human condition. It is human being that becomes the major theme of the dialogue between cosmology and theology.On the basis of the conclusions made the paper discusses some “hot” issues in the contemporary cosmology-theology discussion, including: 1) The inseparability of cosmology and theology in justification of the possibility of cosmological knowledge, 2) Fine-tuning, Anthropic principle, fitness of the universe for life, 3) The unknowability of the universe and apophaticism in cosmology, 4) Multiple universes and their ontology, 5) How much of life is in the universe: the Search for Extraterrestrial Intelligence (SETI), exoplanets and theological consequence for multiple incarnations, 6) The origin of the universe in modern scientific cosmology and its relevance to the theologically understood creatio ex nihilo, 7) Consciousness and the universe: can cosmology account for its own possibility without appealing to the theologically understood human capacity in producing an intellectual synthesis of the universe.Conclusion. On the basis of the methods applied to the hot issues in the dialogue between cosmology and theology one concludes that the dialogue between cosmology and theology is an open-ended enterprise related to the fundamentally concealed origins of humanity and universe. The difference is hermeneutics of the universe does not create any contradiction or tension but reflects a dualistic position of humanity in the universe, being an insignificant part of it and at the same time its center of disclosure and manifestation.

First results from the REAL-time Transient Acquisition backend (REALTA) at the Irish LOFAR station

Modern radio interferometers such as the LOw Frequency ARray (LOFAR) are capable of producing data at hundreds of gigabits to terabits per second. This high data rate makes the analysis of radio data cumbersome and computationally expensive. While high performance computing facilities exist for large national and international facilities, that may not be the case for instruments operated by a single institution or a small consortium. Data rates for next generation radio telescopes are set to eclipse those currently in operation, hence local processing of data will become all the more important. Here, we introduce the REAL-time Transient Acquisition backend (REALTA), a computing backend at the Irish LOFAR station (I-LOFAR) which facilitates the recording of data in near real-time and post-processing. We also present first searches and scientific results of a number of radio phenomena observed by I-LOFAR and REALTA, including pulsars, fast radio bursts, rotating radio transients, the search for extraterrestrial intelligence, Jupiter, and the Sun.

A radio technosignature search towards Proxima Centauri resulting in a signal of interest

The detection of life beyond Earth is an ongoing scientific pursuit, with profound implications. One approach, known as the search for extraterrestrial intelligence (SETI), seeks to find engineered signals (‘technosignatures’) that indicate the existence of technologically capable life beyond Earth. Here, we report on the detection of a narrowband signal of interest at ~982 MHz, recorded during observations towards Proxima Centauri with the Parkes Murriyang radio telescope. This signal, BLC1, has characteristics broadly consistent with hypothesized technosignatures and is one of the most compelling candidates to date. Analysis of BLC1—which we ultimately attribute to being an unusual but locally generated form of interference—is provided in a companion paper. Nevertheless, our observations of Proxima Centauri are a particularly sensitive search for radio technosignatures towards a stellar target.

Analysis of the Breakthrough Listen signal of interest blc1 with a technosignature verification framework

The aim of the search for extraterrestrial intelligence (SETI) is to find technologically capable life beyond Earth through their technosignatures. On 2019 April 29, the Breakthrough Listen SETI project observed Proxima Centauri with the Parkes ‘Murriyang’ radio telescope. These data contained a narrowband signal with characteristics broadly consistent with a technosignature near 982 MHz (‘blc1’). Here we present a procedure for the analysis of potential technosignatures, in the context of the ubiquity of human-generated radio interference, which we apply to blc1. Using this procedure, we find that blc1 is not an extraterrestrial technosignature, but rather an electronically drifting intermodulation product of local, time-varying interferers aligned with the observing cadence. We find dozens of instances of radio interference with similar morphologies to blc1 at frequencies harmonically related to common clock oscillators. These complex intermodulation products highlight the necessity for detailed follow-up of any signal of interest using a procedure such as the one outlined in this work.

Galactic traversability: a new concept for extragalactic SETI

AbstractInterstellar travel in the Milky Way is commonly thought to be a long and dangerous enterprise, but are all galaxies so hazardous? I introduce the concept ofgalactic traversabilityto address this question. Stellar populations are one factor in traversability, with higher stellar densities and velocity dispersions aiding rapid spread across a galaxy. The interstellar medium (ISM) is another factor, as gas, dust grains and cosmic rays all pose hazards to starfarers. I review the current understanding of these components in different types of galaxies, and conclude that red quiescent galaxies without star formation have favourable traversability. Compact elliptical galaxies and globular clusters could be ‘super-traversable’, because stars are packed tightly together and there are minimal ISM hazards. Overall, if the ISM is the major hindrance to interstellar travel, galactic traversability increases with cosmic time as gas fractions and star formation decline. Traversability is a consideration in extragalactic surveys for the Search for Extraterrestrial Intelligence (SETI).

Strategies for Maximizing Detection Rate in Radio SETI

Abstract The Search for Extraterrestrial Intelligence (SETI) is a scientific and cultural effort seeking evidence of intelligent life beyond earth. Radio SETI observes the radio spectrum for “technosignatures” that could be produced by an advanced ET society. This work models radio SETI as an end-to-end system and focuses on narrowband intentional transmissions. We look at strategies to maximize the expected number of detections per year (DPY) of search. Assuming that ET civilizations will be associated with star systems, we want to maximize the number of stars that may be observed at one time. Assuming a representative star density, this requires maximizing the search volume in a cone defined by the detection range and field of view (FOV). The parameter trades are modified from the case where one simply maximizes the signal-to-noise ratio. Instead, a joint optimization between FOV and sensitivity is needed. Some implications: (1) Instead of focusing on the terrestrial microwave window of 1–10 GHz, frequencies below 1 GHz may be optimal for detection rate due to the larger FOV. (2) Arrays of smaller dishes should be favored compared to a single dish of equivalent area. (3) Aperture arrays are desirable due to their large potential FOV. Many radio telescopes under development will provide both high sensitivity and large FOV, and should offer much improved SETI detection rates. Still higher DPY is needed, however, to achieve results in reasonable time horizons, which should be possible by greatly expanding computation capability to the next-generation wide-FOV antenna arrays.

SETI strategy with FAST fractality

We applied the Koch snowflake fractal antenna in planning calibration of the Five-hundred-meter Aperture Spherical radio Telescope (FAST), hypothesizing second-order fractal primary reflectors can optimize the orientated sensitivity of the telescope. Meanwhile, on the grounds of NASA Science Working Group Report in 1984, we reexamine the strategy of Search for Extraterrestrial Intelligence (SETI). A mathematical analysis of the radar equation will be performed in the first section, aiming to make it convenient to design a receiver system that can detect activities of an extraterrestrial civilization, according to the observable region of the narrowband. Taking advantage of the inherent potential of FAST, we simulate the theoretical detection of a Kardashev Type I civilization by a snowflake-selected reflecting area (Drake et al.).

A Dyson sphere around a black hole

ABSTRACT The search for extraterrestrial intelligence (SETI) has been conducted for nearly 60 yr. A Dyson sphere, a spherical structure that surrounds a star and transports its radiative energy outwards as an energy source for an advanced civilization, is one of the main targets of SETI. In this study, we discuss whether building a Dyson sphere around a black hole is effective. We consider six energy sources: (i) the cosmic microwave background, (ii) the Hawking radiation, (iii) an accretion disc, (iv) Bondi accretion, (v) a corona, and (vi) relativistic jets. To develop future civilizations (for example, a Type II civilization), $4\times 10^{26}\, {\rm W}(1\, {\rm L_{\odot }})$ is expected to be needed. Among (iii) to (vi), the largest luminosity can be collected from an accretion disc, reaching $10^{5}\, {\rm L_{\odot }}$, enough to maintain a Type II civilization. Moreover, if a Dyson sphere collects not only the electromagnetic radiation but also other types of energy (e.g. kinetic energy) from the jets, the total collected energy would be approximately 5 times larger. Considering the emission from a Dyson sphere, our results show that the Dyson sphere around a stellar-mass black hole in the Milky Way ($10\, \rm kpc$ away from us) is detectable in the ultraviolet $(\rm 10{-}400\, {\rm nm)}$, optical $(\rm 400{-}760\, {\rm nm)}$, near-infrared ($\rm 760\, {\rm nm}{-}5\, {\rm \mu m}$), and mid-infrared ($\rm 5{-}40\, {\rm \mu m}$) wavelengths via the waste heat radiation using current telescopes such as Galaxy Evolution Explorer Ultraviolet Sky Surveys. Performing model fitting to observed spectral energy distributions and measuring the variability of radial velocity may help us to identify these possible artificial structures.

The Breakthrough Listen Search for Intelligent Life: Searching for Technosignatures in Observations of TESS Targets of Interest

Abstract Exoplanetary systems are prime targets for the Search for Extraterrestrial Intelligence (SETI). With the recent uptick in the identification of candidate and confirmed exoplanets through the work of missions like the Transiting Exoplanet Survey Satellite (TESS), we are beginning to understand that Earth-like planets are common. In this work, we extend the Breakthrough Listen (BL) search for extraterrestrial intelligence to include targeted searches of stars identified by TESS as potential exoplanet hosts. We report on 30 minute cadence observations collected for 28 targets selected from the TESS Input Catalog from among those identified as containing signatures of transiting planets. The targets were searched for narrowband signals from 1 to 11 GHz using the turboSETI pipeline architecture modified for compatibility with the Google Cloud environment. Data were searched for drift rates of ±4 Hz s−1 above a minimum signal-to-noise threshold of 10, following the parameters of previous searches conducted by Price et al. and Enriquez et al. The observations presented in this work establish some of the deepest limits to date over such a wide band (1–11 GHz) for life beyond Earth. We determine that fewer than 12.72% of the observed targets possess transmitters operating at these frequencies with an equivalent isotropic radiated power greater than our derived threshold of .