In this paper it is analysed which of the thousands of stars in the WOW! Signal region could have the highest chance of being the real source of the signal, providing that it came from a star system similar to ours. A total of 66 G and K-type stars are sampled, but only one of them is identified as a potential Sun-like star considering the available information in the Gaia Archive. This candidate source, which is named 2MASS 19281982-2640123, therefore becomes an ideal target to conduct observations in the search for techno-signatures. Another two candidate stars have a luminosity error interval that includes the luminosity of the Sun, and 14 candidates more are also identified as potential Sun-like stars, but the estimations on their luminosity were unknown.

Interstellar 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 of galactic traversability to 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).

In SETI, when searching for ‘beacons’ – transmissions intended for us and meant to get our attention – one must guess the appropriate frequency to search by considering what frequencies would be universally obvious to other species. This is a well-known concept in game theory, where such solutions to a non-communicative cooperative game (such as a mutual search) are called ‘Schelling points’. It is noteworthy, therefore, that when developing his eponymous units, Planck called them ‘natural’ because they ‘remain meaningful for all times and also for extraterrestrial and non-human cultures’. Here, I apply Planck's suggestion in the context of Schelling points in SETI with a ‘Planck Frequency Comb’, constructed by multiplying the Planck energy by integer powers of the fine structure constant. This comb includes a small number of frequencies in regions of the electromagnetic spectrum where laser and radio SETI typically operates. Searches might proceed and individual teeth in the comb, or at many teeth at once, across the electromagnetic spectrum. Indeed, the latter strategy can be additionally justified by the transmitter's desire to signal at many frequencies at once, to improve the chances that the receiver will guess one of them correctly. There are many arbitrary and anthropocentric choices in this comb's construction, and indeed one can construct several different frequency combs with only minor and arbitrary modifications. This suggests that it may be fruitful to search for signals arriving in frequency combs of arbitrary spacing. And even though the frequencies suggested here are only debatably ‘better’ than others proposed, the addition of the Planck Frequency Comb to the list of ‘magic frequencies’ can only help searches for extraterrestrial beacons.

In this work we address the problem of estimating the probabilities of causal contacts between civilizations in the Galaxy. We make no assumptions regarding the origin and evolution of intelligent life. We simply assume a network of causally connected nodes. These nodes refer somehow to intelligent agents with the capacity of receiving and emitting electromagnetic signals. Here we present a three-parametric statistical Monte Carlo model of the network in a simplified sketch of the Galaxy. Our goal, using Monte Carlo simulations, is to explore the parameter space and analyse the probabilities of causal contacts. We find that the odds to make a contact over decades of monitoring are low for most models, except for those of a galaxy densely populated with long-standing civilizations. We also find that the probability of causal contacts increases with the lifetime of civilizations more significantly than with the number of active civilizations. We show that the maximum probability of making a contact occurs when a civilization discovers the required communication technology.

The search for Dyson Spheres has been propelled not only by the hope of discovering intelligent alien life, but by humanity's ever-increasing need for energy. However, the Dyson Sphere is not a practical design, requiring too much matter to build and too much energy to stabilize. Here we discuss the various designs of a Dyson Sphere and propose the Solar Wind Power (SWP) Satellite, a simplistic, self-sustaining system that draws power from the solar wind and uses a laser to fire energy to collectors (on space stations, bases, etc.) positioned anywhere in the Solar System. While a small SWP Satellite can provide an estimated 2 MW of power, larger (or networks of) satellites could provide terawatts of power or more. The cost of the SWP Satellite would be relatively cheap – it primarily consists of shaped copper, with only a few complex systems onboard. Detection of such a satellite would be difficult using current technology, because at this time we can only detect solar wind deviations of up to 10−13 MS yr−1, while a 2 MW satellite would only divert 10−34 MS yr−1. Thus, only very large SWP Satellites could possibly be detected.

The number of habitable planets in the Milky Way and its temporal variation are major unknowns in the nascent fields of astrobiology and Search for ExtraTerrestrial Intelligence studies. All numerical models developed thus far have suffered from large uncertainties in the input data, in addition to our lack of understanding of the processes of astrobiological dynamics. Here, we argue that at least the input data can now be specified with more confidence, and use a simple Monte Carlo model of the Galactic Habitable Zone (GHZ) as a flexible platform for their elucidation. Previous papers have described some of the major results of this class of models; in this paper we present its mechanics and input parameters, notably the number of the habitable planets in the GHZ and their temporal distribution, based on the results of Lineweaver et al. (Lineweaver, C.H., Fenner, Y. & Gibson, B.K. (2004). Science303, 59–62.) Regulation mechanisms (such as gamma-ray bursts or supernovae) and their temporal evolution, assumed to be main agents responsible for large-scale correlation effects, are modelled as type α (which can sterilize part of or the entire GHZ) and type β (which are of local importance) events with decreasing mean temporal frequency over the cosmological timescale. The considered global risk function implies as an upper limit that about one out of a hundred habitable sites will achieve high astrobiological complexity. The preliminary results of numerical modelling presented here and elsewhere imply that the lack of a sudden change from an essentially dead Galaxy to a Galaxy filled with complex life – the astrobiological phase transition – in our past (a version of Fermi's paradox) may be understood as a consequence of global astrobiological disequilibrium, strongly indicating such a transitional epoch in our future.