When we’ve discussed interstellar ‘interlopers’ like ‘Oumuamua and 2I/Borisov, the science fiction-minded among us have now and then noted Arthur Clarke’s Rendezvous with Rama (Gollancz, 1973). Although we’ve yet to figure out definitively what ‘Oumuamua is (2/I Borisov is definitely a comet), the Clarke reference is an imaginative nod to the possibility that one day an alien craft might enter our Solar System during a gravitational assist maneuver and be flung outward on whatever its mission was (in Rama’s case, out in the direction of the Large Magellanic Cloud). Since we’ll never see ‘Oumuamua again, we wait with great anticipation the work of the Legacy Survey of Space and Time (LSST), which will be run via the Vera Rubin Telescope (first light in 2025). Estimates vary widely but the consensus seems to be that with a telescope capable of imaging the entire visible sky in the southern hemisphere every few nights, the LSST should produce more than a few interstellar objects,...

If you had to choose, which planetary system would you gauge most likely to house a life-bearing planet: Proxima Centauri or TRAPPIST-1? The question is a bit loaded given that there are seven TRAPPIST-1 planets, hence a much higher chance for success there than in a system that (so far) has produced evidence for only two worlds. But there are other factors having to do with the delivery of prebiotic materials by comet, which is the subject of a new paper from Richard Anslow (Cambridge Institute of Astronomy). “It’s possible that the molecules that led to life on Earth came from comets,’’ Anslow reminds us, “so the same could be true for planets elsewhere in the galaxy.” So let’s untangle this a bit. We don’t know whether comets are vital to the origin of life on Earth or any other world, and Anslow (working with Cambridge colleagues Amy Bonsor and Paul B. Rimmer) does not argue that they are. What their paper does is to examine the environments most likely to be affected by cometary...

Given that interstellar communications have been on my mind recently, I was delighted to receive this essay from Don Wilkins. Based in St. Louis, where he is a now-retired aerospace engineer, Don has plenty of experience in avionics and has the chops to know how to make widely-dispersed aircraft talk to each other. Here his scope is a bit wider: What are the implications of 'lurker' probes, the conceivably ancient (or newer) technologies from an extraterrestrial civilization that might be monitoring our planet? If such exist, their communications become a SETI target, and the question of how their network might operate is an intriguing one. I had no idea, for example, that the idea of gravitational lensing for such communications had made its way into the SETI field, but Don here acquaints us with several studies that tackle the concept, along with other insights as found below. by Don Wilkins If an expansionist star faring civilization exists, it is likely to construct an...

Writers have modeled the arrival of an extraterrestrial probe in our Solar System in a number of interesting science fiction texts, from Clarke’s Rendezvous with Rama (1973) to the enigmatic visitors of Ted Chiang’s "Story of Your Life,” which Hollywood translated into the film Arrival (2016). In between I might add the classic ‘saucer landing on the White House lawn’ trope of The Day the Earth Stood Still (1951), based on a Harry Bates short story. All these and many other stories raise the question: What if before we make a radio or optical SETI detection, an extraterrestrial scout actually shows up? Graeme Smith (UC: Santa Cruz) goes to work on the idea in a recent paper in the International Journal of Astrobiology, where he focuses on the mechanism of interstellar dispersion. The model has obvious ramifications for ourselves. We are beings who have begun probing nearby space with vehicles like Pioneer and Voyager, and in our early stages of exploration we could conceivably be...

I don’t suppose that Frank Drake intended his famous Drake Equation to be anything more than a pedagogical device, or rather, an illustrative tool to explain what he viewed as the most significant things we would need to know to figure out how many other civilizations might be out there in the galaxy. This was back in 1961, and naturally the equation was all about probabilities, because we didn’t have hard information on most of the factors in the equation. Drake was already searching for radio signals at Green Bank, in the process inventing SETI as practiced through radio telescopes. The factors here should look familiar to most Centauri Dreams readers, but let’s run through them, because among the old hands here we also get an encouraging number of students and people new to the field. N is the number of civilizations with communications potential in the galaxy, with R* the rate of star formation, fp the fraction of stars with planets, ne the number of planets that can support life...

The problem of perspective haunts SETI, and in particular that branch of SETI that has been labeled Dysonian. This discipline, based on Freeman Dyson’s original notion of spheres of power-gathering technology enclosing a star, has given rise to the ongoing search for artifacts in our astronomical data. The fuss over KIC 8462852 (Boyajian’s Star) a few years back involved the possibility that it was orbited by a megastructure of some kind, and thus a demonstration of advanced technology. Jason Wright and team at Penn State have led searches, covered in these pages, for evidence of Dyson spheres in other galaxies. The Dysonian search continues to widen. I cite a problem of perspective in that we have no real notion of what we might find if we finally locate signs of extraterrestrial builders in our data. It’s so comfortable to be a carbon-based biped, but the entities we’re trying to locate may have other ways of evolving. Clément Vidal, a French philosopher and one of the most...