Extraterrestrial Intelligence Research Articles

Geopolitical Implications of a Successful SETI Program

We discuss the recent “realpolitik” analysis of Wisian and Traphagan (2020) of the potential geopolitical fallout of the success of the Search for Extraterrestrial Intelligence (SETI). They conclude that “passive” SETI involves an underexplored yet significant risk. This is the risk that, in the event of a successful, passive detection of extraterrestrial technology, state-level actors could seek to gain an information monopoly on communications with an extraterrestrial intelligence. These attempts could lead to international conflict and potentially disastrous consequences. In response to this possibility, they argue that scientists and facilities engaged in SETI should preemptively engage in significant security protocols to forestall this risk. We find several flaws in their analysis. While we do not dispute that a realpolitik response is possible, we uncover concerns with Wisian and Traphagan's presentation of the realpolitik paradigm, and we argue that sufficient reason is not given to justify treating this potential scenario as action-guiding over other candidate geopolitical responses. Furthermore, even if one assumes that a realpolitik response is the most relevant geopolitical response, we show that it is highly unlikely that a nation could successfully monopolize communication with ETI. Instead, the real threat that the authors identify is based on the perception by state actors that an information monopoly is likely. However, as we show, this perception is based on an overly narrow contact scenario. Overall, we critique Wisian and Traphagan's argument and resulting recommendations on technical, political, and ethical grounds. Ultimately, we find that not only are Wisian and Traphagan's recommendations unlikely to work, they may also precipitate the very ills that they foresee. As an alternative to the Wisian and Traphagan recommendations, we recommend transparency and data sharing (which are consistent with currently accepted best practices), further development of postdetection protocols, and better education of policymakers in this space.

Drift Rates of Narrowband Signals in Long-term SETI Observations for Exoplanets

The Doppler shift of a radio signal is caused by the relative motion between the transmitter and receiver. The change in frequency of the signal over time is called the drift rate. In the studies of radio search for extraterrestrial intelligence (SETI), extraterrestrial narrowband signals are expected to appear “chirped” since both the exoplanet and Earth are moving. Such planet rotation and orbital revolution around the central star can cause a nonzero drift rate. Other relative motions between the transmitter and receiver, such as the gravitational redshift and galactic potential, are negligible. In this paper, we mainly consider the common cases in which the drift rate is contributed by the rotations and orbits of Earth and the exoplanet in the celestial mechanics perspective, and we briefly discuss other cases different from the Earth–exoplanet one. We can obtain the expected pseudosinusoidal drifting result with long-term observations and shorter orbital periods of exoplanets. Exoplanets with higher orbital eccentricities can cause asymmetric drifting. The expected result should be intermittent pseudosinusoidal curves in long-term observations. The characteristics of pseudosinusoidal curves, as another new criterion for extraterrestrial signals, can be applied to long-term SETI reobservations in future research.

Constraints on extragalactic transmitters via Breakthrough Listen observations of background sources

ABSTRACT The Breakthrough Listen Initiative has embarked on a comprehensive Search for Extraterrestrial Intelligence (SETI) survey of nearby stars in the Milky Way that is vastly superior to previous efforts as measured by a wide range of different metrics. SETI surveys traditionally ignore the fact that they are sensitive to many background objects, in addition to the foreground target star. In order to better appreciate and exploit the presence of extragalactic objects in the field of view, the aladin sky atlas and NASA/IPAC Extragalactic Database (NED) were employed to make a rudimentary census of extragalactic objects that were serendipitously observed with the 100-m Green Bank Telescope observing at 1.1–1.9 GHz. For 469 target fields [assuming a full width at half-maximum (FWHM) radial field of view of 4.2 arcmin], NED identified a grand total of 143 024 extragalactic objects, including various astrophysical exotica e.g. active galactic nuclei (AGN) of various type, radio galaxies, interacting galaxies, and one confirmed gravitational lens system. Several nearby galaxies, galaxy groups, and galaxy clusters are identified, permitting the parameter space probed by SETI surveys to be significantly extended. Constraints are placed on the luminosity function of potential extraterrestrial transmitters assuming it follows a simple power law and limits on the prevalence of very powerful extraterrestrial transmitters associated with these vast stellar systems are also determined. It is demonstrated that the recent Breakthrough Listen Initiative, and indeed many previous SETI radio surveys, places stronger limits on the prevalence of extraterrestrial intelligence in the distant Universe than is often fully appreciated.

Sensitive Multibeam Targeted SETI Observations toward 33 Exoplanet Systems with FAST

As a major approach to looking for life beyond the Earth, the search for extraterrestrial intelligence (SETI) is committed to searching for technosignatures such as engineered radio signals that are indicative of technologically capable life. In this paper, we report a targeted SETI campaign employing an observation strategy named multibeam coincidence matching at the Five-hundred-meter Aperture Spherical radio Telescope toward 33 known exoplanet systems, searching for ETI narrowband drifting signals across 1.05–1.45 GHz in two orthogonal linear polarization directions separately. A signal at 1140.604 MHz detected from the observation toward Kepler-438 originally piqued our interest because its features are roughly consistent with assumed ETI technosignatures. However, evidences such as its polarization characteristics are able to eliminate the possibility of an extraterrestrial origin. Our observations achieve an unprecedented sensitivity because the minimum equivalent isotropic radiated power we are able to detect reaches 1.48 × 109 W.

Extraterrestrial intelligence and moral standing

AbstractWe consider the Search for ExtraTerrestrial Intelligence (SETI) activities from a bioethical standpoint. In particular, we argue that there is a moral duty to search for other intelligent beings in the Universe. Some of them could – and are likely to be – morally enhanced in the sense that they are not only capable of unmistakable moral reasoning but are also capable of consistently acting upon the results of such deliberations. Even if the probability of finding such morally superior beings is small, it is higher than zero in any case; in fact, our astrobiological knowledge suggests that this probability is significant. Hence, there are both deductive and inductive arguments for the proposition that our duty is to search for such morally superior extraterrestrial beings. In other words, there is a duty to undertake and support our SETI efforts. The argument to that effect runs parallel to some of the arguments deployed in current debates on human moral enhancement.

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.

If extraterrestrial intelligence exists, it is unable to recognize humans as intelligent beings – ERRATUM

If extraterrestrial intelligence exists, it is unable to recognize humans as intelligent beings – ERRATUM

If extraterrestrial intelligence exists, it is unable to recognize humans as intelligent beings

AbstractIn this paper we consider a scenario in which Carl Sagan's Copernican principle is more likely than its negation. Thus, assuming that the existence of an extraterrestrial intelligence (ETI) is reasonably likely, the paper considers the possibility of an ETI that is unable to recognize humans as intelligent beings. The paper presents the rationale for such an assumption. It also discusses the possible consequences for humanity of such a scenario. In this paper, we argue why the scenario under discussion is actually more positive for humanity than a scenario in which ETI would be capable of recognizing humanity as an intelligent species. We also point to feminist approaches to SETI issues exposing the role played by the specific evolutionary and developmental context of potential ETI.

SETI From the Perspective of Intercivilizational Politics

The possibility of SETI finding extraterrestrial biological or technological signatures is becoming less hypothetical. Social science scholarship has responded with a growing literature that examines the possible social, cultural, and political implications of a major SETI discovery. This article extends this social science perspective by speculating about politics at the other end of contact. I argue that the questions of whether another civilization would apply resources to SETI like efforts, who they would wish to contact, and their motivations for searching for intelligent life, are essentially questions about the politics of possible but unknown societies.I attempt to show the utility of this comparative politics perspective by applying it to Fermi's Paradox. The perspective of intercivilizational politics reframes the paradox as a problem of collective action and avoids two problematic assumptions widely found in the literature. First, it is probably impossible to predict what would be rational for extraterrestrial intelligence without knowing their appetite for risk. Second, if an extraterrestrial civilization shares similar patterns to our development, then many proposed solutions to Fermi's Paradox fall into the trap of assuming a unified rational actor. Instead, it is likely that possible interlocutors represent different political and social institutions from across an exocivilization.In addition, many famous commentators have argued that contact with another civilization would likely be disastrous for the less developed party, presumably us. So far, political scientists have added to this discussion by elaborating further on the possible dangers of a SETI discovery. However, I argue that reframing SETI efforts within the context of intercivilizational politics mitigates some of these concerns.

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

Migrating extraterrestrial civilizations and interstellar colonization: implications for SETI and SETA

AbstractAdvanced extraterrestrial civilizations may produce observable technosignatures when they migrate inside their planetary systems and to other planetary systems. Collectively, the search for technosignatures produced by migrating extraterrestrial civilizations can be described as the search for migrating extraterrestrial intelligence (SMETI). I propose that extraterrestrial civilizations may use free-floating planets as interstellar transportation to reach, explore and colonize planetary systems. I propose possible technosignatures and artefacts that may be produced by extraterrestrial civilizations using free-floating planets for interstellar migration and interstellar colonization, as well as strategies for the search for their technosignatures and artefacts. I discuss technosignatures that may be produced by extraterrestrial civilizations using other methods of interstellar migration and colonization. As an example, I discuss the star GJ 433, which experienced a close flyby a few thousand years ago. I divide possible technosignatures of migrating civilizations into groups to highlight similarities and differences among technosignatures produced by civilizations using different methods of migration and interstellar colonization. It follows from the comparison, for example, that interstellar migration using flybys of stars can blend with interstellar migration using free-floating planets.

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.

Research programmes arising from ‘Oumuamua considered as an alien craft

AbstractThe controversial hypothesis that ‘Oumuamua (1I/2017 U1) was an alien craft dominated by a solar sail is considered using known physics for the two possible cases: controlled and uncontrolled flight. The reliability engineering challenges for an artefact designed to operate for ~105–106 year are also considerable. All three areas generate research programmes going forward. The uncontrolled case could be either ‘anonymous METI’ (messaging extraterrestrial intelligence) or ‘inadvertent METI’. In the controlled case the nature of the origin star, trajectory guidance from the origin star to the Sun, and the identity of a destination star are all undecided. The ‘controlled’ case has more strikes against it than the ‘uncontrolled’ case, but neither suffers a knock-out blow, as yet. Some of the issues turn out not to be major obstacles to the alien craft hypothesis, but others weaken the case for it. Most, however, imply new studies. Some of these, e.g. intercept missions for new interstellar objects, are concepts being developed, and will be of value whatever these objects turn out to be. Overall, these considerations show that a many-pronged, targeted, research programme can be built around the hypothesis that ‘Oumuamua is an alien craft. The considerations presented here can also be applied to other interstellar visitors, as well as to general discussions of interstellar travel.

Cosmic Queries: StarTalk's Guide to Who We Are, How We Got Here, and Where We’re Going

Cosmic Queries: StarTalk's Guide to Who We Are, How We Got Here, and Where We’re Going

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.