In the last two days we’ve looked at a discussion of a possible SETI observable, a ‘shielding swarm’ that an advanced civilization might deploy in the event of a nearby supernova. As with Richard Carrigan’s pioneering searches for Dyson swarms in the infrared, this kind of SETI makes fundamentally different assumptions than the SETI we’ve grown familiar with, where the hope is to snag a beacon-like signal at radio or optical wavelengths. So-called ‘Dysonian SETI’ assumes no intent to communicate. It is about observing a civilization’s artifacts.
Both radio/optical SETI and this Dysonian effort are worth pursuing, because we have no idea what the terms of any discovery of an extraterrestrial culture will be. The hope of receiving a deliberate signal carries the enthralling possibility that somewhere there is an Encyclopedia Galactica that we may one day gain access to, or at the least that there is a civilization that wants to talk to us. A Dysonian detection would tell us that civilizations can survive their youth to become builders on a colossal scale, pushing up toward Kardashev levels II and III.
Keeping both SETI tracks engaged is good science. It’s encouraging on the radio front to see that the Parkes radio telescope in Australia has now joined the Green Bank Telescope (West Virginia) and the Automated Planet Finder (Lick Observatory) in SETI observations funded by Breakthrough Listen. A key component of the Breakthrough Initiatives effort (which includes Breakthrough Starshot), Breakthrough Listen has just announced the activation of its SETI project at Parkes with observations of the newly discovered planet around Proxima Centauri.
About this study, several points. First, Parkes marks a welcome expansion of the northern hemisphere efforts. Situated about 20 kilometers north of the town of Parkes in New South Wales, the telescope can observe those parts of the sky that are not visible to its northern counterparts, making it a major component in any comprehensive SETI effort.
Image: The Parkes radio telescope in New South Wales. Credit: CSIRO.
As to Proxima Centauri, we now have an Earth-sized planet orbiting in what appears to be its habitable zone, meaning that temperatures could allow liquid water to exist on its surface. The discovery of Proxima b has enlivened the interstellar community as we examine ways to learn more about it, including the Breakthrough Starshot flyby probe studies. But I think we can agree that the chances of finding a civilization on any particular planet are low.
So says Andrew Siemion, director of the Berkeley SETI Research Center and leader of the Breakthrough Listen science program. And he adds:
“…once we knew there was a planet right next door, we had to ask the question, and it was a fitting first observation for Parkes. To find a civilisation just 4.2 light years away would change everything.”
It was in the same spirit that a number of SETI instruments have been turned to Boyajian’s Star (KIC 8462852), whose unusual light curves have drawn a great deal of attention because we have so far been unable to explain them. In both cases, we have a high-interest target, in the Proxima system because of its sheer proximity to Earth and in the Boyajian’s Star system because one explanation for those light curves is intelligent engineering.
So I am all for examining Proxima Centauri even though I think the real action there will be in one day analyzing its atmosphere for signs of biosignatures. 14 days of commissioning and test observations at Parkes led up to the first observation of Proxima on November 8 (local time). The broader strategy is to continue the SETI effort at radio wavelengths across a wide range of targets, as listed in this Breakthrough Initiatives news release.
All 43 stars (at south declinations) within 5 parsecs, at 1-15 GHz. Sensitive to the levels of radio transmission at which signals ‘leak’ from Earth-based radar transmitters (with available receivers).
1000 stars (south) of all spectral-types (OBAFGKM) within 50 parsecs (1-4 GHz).
One Million Nearby Stars (south). In 2016-2017, first 5,000 stars; 1 minute exposure (1-4 GHz).
Galactic plane and Center (1-4 GHz).
Centers of 100 nearby galaxies (south declinations): spirals, ellipticals, dwarfs, irregulars (1-4 GHz).
Exotic sources will include white dwarfs, neutron stars, black holes, and other anomalous natural sources (1-4 GHz).
Bear in mind as these efforts proceed that Breakthrough Listen will also be coordinating searches with the FAST (Five hundred meter Aperture Spherical Telescope) in southwest China, exchanging observing plans, search methods and data. Thus we move toward a global SETI effort that can quickly share promising signals for analysis. Data from Parkes and the other Breakthrough Listen telescopes will be made available to the public online.
It was inevitable that KIC 8462852 would spawn a nickname, given the public attention given to this mystifying star, whose unusual lightcurves continue to challenge us. ‘Tabby’s Star’ is the moniker I’ve seen most frequently, but we now seem to be settling in on ‘Boyajian’s Star.’ It was Tabetha Boyajian (Louisiana State) whose work with the Planet Hunters citizen science project brought the story to light, and in keeping with astronomical naming conventions (Kapteyn’s Star, Barnard’s Star, etc.), I think the use of the surname is appropriate.
Planet Hunters works with Kepler data, looking for any dimming of the 150,000 monitored stars that may have gone undetected by the automated routines that hunt for repeating patterns. Boyajian’s Star cried out for analysis, dimming in odd ways that flagged not the kind of planetary transit across the face of a stellar disk that researchers expected but something else, something that would make the star dim by as much as 22 percent, and at irregular intervals. That led to a variety of hypotheses, the best known of which is a large group of comets, but we also have evidence that the star has been dimming at a steady rate.
Image: Tabetha Boyajian, looking up, presumably at Boyajian’s Star (caption swiped from Jason Wright’s page at Penn State).
With the story this unsettled, this morning’s energizing news is that Boyajian’s Star is now being examined by Breakthrough Listen. Working with Jason Wright, now a visiting astronomer at UC Berkeley, as well as Boyajian herself, the SETI project intends to devote hours of listening time on the Green Bank radio telescope in West Virginia to the star. You’ll recall that Breakthrough Listen is the $100 million SETI effort funded by the Breakthrough Prize Foundation and its founder, investor Yuri Milner. The Breakthrough Starshot project described often in these pages is also a Breakthrough Prize Foundation initiative.
As Andrew Siemion (director of the Berkeley SETI Research Center and co-director of Breakthrough Listen) explains in the video above, the project has access to the most powerful SETI equipment available, meaning its scientists can study Boyajian’s Star at the highest levels of sensitivity across a wide range of possible signal types. But the Green Bank effort will hardly be the first, for Boyajian’s Star has already excited a great deal of interest, as Siemion explains:
“Everyone, every SETI program telescope, I mean every astronomer that has any kind of telescope in any wavelength that can see Tabby’s star has looked at it. It’s been looked at with Hubble, it’s been looked at with Keck, it’s been looked at in the infrared and radio and high energy, and every possible thing you can imagine, including a whole range of SETI experiments. Nothing has been found.”
In Green Bank, Breakthrough Listen has access to the largest fully steerable radio telescope on the planet. Observations are scheduled for eight hours per night for three nights in the next two months, the first having taken place on October 26. The plan is to gather as much as 1 petabyte of data over hundreds of millions of individual radio channels. Siemion describes a new SETI instrument that can examine “…many gigahertz of bandwidth simultaneously and many, many billions of different radio channels all at the same time so we can explore the radio spectrum very, very quickly.”
Breakthrough Listen will be observing using four different radio receivers on the Green Bank instrument in a frequency range from 1 to 12 GHz, a range beginning, Siemion says, at about where cell phones operate up through the frequencies used for satellite TV signals.
Image: The Green Bank Radio Telescope (GBT) focuses 2.3 acres of radio light. It is 148 meters tall, nearly as tall as the nearby mountains and much taller than pine trees in the national forest. The telescope is in a valley of the Allegheny mountains to shield the observations from radio interference. Credit: NRAO/AUI.
Yesterday’s live video chat from Green Bank with Tabetha Boyajian, Jason Wright and Andrew Siemion is now available online, with the trio answering questions about the ongoing study. Boyajian was asked as the session opened how many comets it would take to reproduce the effects being observed around KIC 8462852. The answer: Hundreds to thousands of “very giant comets” just to reproduce the last 30 days of the data.
The numbers give no particular credence to the idea that we may be looking at some kind of artificial construction project around Boyajian’s Star, but they do underline how mysterious are the processes, assuming they are natural, that are driving this phenomenon. Boyajian called the comet hypothesis ‘pretty outrageous,’ but went on to say that of all the explanations, it is the one she most favors, as all other explanations are likewise outrageous.
On that score, I want to mention Jason Wright’s paper, written with Steinn Sigurðsson at Penn State, looking at other possible solutions to the Boyajian’s Star puzzle. It’s particularly useful early on in a section devoted to the follow-up work that has occurred, including the SETI studies with the VERITAS gamma-ray observatory, the Allen Telescope Array and the Boquete Optical SETI Observatory, but also reprising the interesting controversy over the dimming of the star. If you need to catch up with Boyajian’s Star, this is the place.
Wright and Sigurðsson conclude that long-term dimming would not fit well with the comet hypothesis, leaving us still searching for an answer. What does work its way up the chain of plausibility? An unusually dense region of the interstellar medium or a chance alignment with a localized molecular cloud occurring between us and the star is in the mix. The latter might be a so-called ‘Bok globule,’ an isolated and dark nebula dense with dust and gas.
The comet hypothesis is still in play, but a number of other explanations are problematic:
Less compelling, but difficult to rule out, are intrinsic variations due to spots, a “return to normal” from a temporary brightening (due to, perhaps, a stellar merger) and a cloud of material in the outer solar system. We find instrumental effects, other intrinsic variation in Boyajian’s Star, and obscuration by a disk around an orbital companion to Boyajian’s Star very unlikely to be responsible.
Read the paper for the entire list, which includes, with plausibility listed as unclear, the idea of artificial structures (“Would find support if all natural hypotheses are ruled out, we detect signals, or if star suffers significant achromatic extinction.”) The paper is Wright and Sigurðsson, “Families of Plausible Solutions to the Puzzle of Boyajian’s Star,” accepted at the Astrophysical Journal (preprint). But see also Jason Wright’s 10-part popular summary on Boyajian’s Star, which goes through all the options.
If you’ve been following the KIC 8462852 story, you’ll want to be aware of Paul Carr’s Dream of the Open Channel blog, as well as his Wow! Signal Podcast, both of which make for absorbing conversation. In his latest blog post, Carr offers sensible advice about how to look at anomalies in our astronomical data. Dysonian SETI tries to spot such anomalies in hopes of uncovering the activities of an extraterrestrial civilization, but as Carr makes clear, this is an enterprise that needs to be slowly and patiently done, without jumping to any unwarranted assumptions.
Let me quote Carr on this important point:
…we will have to be patient, since we will be almost certainly be wrong at first, or perhaps just unlucky in our search. We don’t need to nail it exactly, but we will need to develop rough models of ET activity that distinguishes it from nature. These models would more or less fit the data that we think anomalous, would make testable predictions, and would show how to rule out at least known natural phenomena. Such a family of models may be available next year, or it may be in 100 years, but the more anomalous data we have, the more the models can be constrained.
This paragraph gets it right, taking it as a given that we have no idea whether there are extraterrestrial civilizations or, for that matter, life of any kind around other stars. We certainly have no idea how widespread either form of life might be, and in the case of Dysonian SETI, we would be looking at technologies so far in advance of ours that recognizing them for what they are (or might be) creates myriad challenges. So while we try to distinguish natural phenomena from the possibility of intelligent activity, we need to keep these profound limitations in mind.
Tabby’s Star, then, is a wonderful case in point, certainly a motivator for this kind of research (and, as we’ve seen, one capable of being sustained at least modestly by public funding), but we should also consider it in a broader perspective. The goal will be to build a catalog of unusual phenomena that can be consulted as we begin to differentiate among such targets. We may discover that all of these can be accounted for by natural processes, and if so, then we have learned something valuable about the universe. No small accomplishment, that.
Red Dwarfs and Astrobiology
Looking beyond SETI to more fundamental questions of astrobiology, we find ourselves in that unsettling period when we have instruments in the pipeline that can tell us much about the exoplanets we observe, but we’re not yet receiving the data that can make a definitive call on the existence of life elsewhere. Astrobiology will accumulate data at increasingly fine levels of detail as we move from missions like Kepler to searches around closer stars. Meanwhile, we have to tune up our models for detecting biosignatures as we wait for the technology to test them.
Here the Transiting Exoplanet Survey Satellite (TESS) comes to mind, as does PLATO (PLAnetary Transits and Oscillations of stars), and of course the James Webb Space Telescope. TESS is due for a 2017 launch, JWST for 2018 and PLATO for 2024. WFIRST (Wide Field Infrared Survey Telescope), scheduled for the mid-2020s, is likewise going to provide key exoplanet observations, and let’s not neglect the small photometric platform CHEOPS (CHaracterising ExOPlanet Satellite), which will sharpen the target lists of future ground-based observatories. We need to continue refining our answers to this question: What does life do to a planet that offers a key observable, and what are the best instruments to detect it.
Red dwarfs make excellent targets if we’re studying a planetary atmosphere to learn whether or not there are biomarkers there, and now we have a new paper from Avi Loeb (Harvard-Smithsonian Center for Astrophysics) that asks whether such stars may ultimately become home to the vast majority of cosmic civilizations. Working with Rafael Batista and David Sloan (both at Oxford University), Loeb acknowledges the obvious: We don’t know if stars like these can support life, and the authors call for building the datasets to find out. But if they can, then the implications are that most life in deep space will eventually be around such stars.
I say ‘eventually’ because M-dwarfs have lifetimes measured in the trillions of years, much greater than the 10 billion years or so that G-class dwarfs like our Sun can expect. And of course, around our own star life gets problematic within about a billion years. We have a planet that cannot be expected to remain habitable all the way to the last days of the Sun.
If life can form on planets around red dwarfs, then the probability of life grows much higher as we go further and further into the future, for these small stars are the most common kind of star in the galaxy, comprising as much as 80 percent of the stellar population. That would mean we are early to the dance, and a densely populated galaxy has simply not had time to develop. Loeb’s paper calculates the relative formation probability per unit time of habitable Earth-like planets within a fixed comoving volume of the Universe and finds red dwarfs favored:
“If you ask, ‘When is life most likely to emerge?’ you might naively say, ‘Now,'” says Loeb. “But we find that the chance of life grows much higher in the distant future.”
Image: This artist’s conception shows a red dwarf star orbited by a pair of habitable planets. Because red dwarf stars live so long, the probability of cosmic life grows over time. As a result, Earthly life might be considered “premature.” Credit: Christine Pulliam (CfA).
Hence the importance of a biosignature detection. If we find such markers in the atmosphere of a red dwarf, we have learned something not only about that particular star, but about the prospect of life in later cosmic eras up to the ten trillion year lifetime of the average red dwarf. The universe we see has had 13.7 billion years to produce life, but we can only imagine what kinds of life might emerge in the future. As for the probability of our own emergence, let me quote from the paper:
One can certainly contend that our result presumes our existence, and we therefore have to exist at some time. Although our result puts the probability of finding ourselves at the current cosmic time within the 0.1% level, rare events do happen. In this context, we reiterate that our results are an order of magnitude estimate based on the most conservative set of assumptions within the standard ?CDM model.
Conservative indeed, and if we tweak the assumptions, it gets more extreme:
If one were to take into account more refined models of the beginning of life and observers, this would likely push the peak even farther into the future, and make our current time less probable. As an example, one could consider that the beginning of life on a planet would not happen immediately after the planet becomes ‘habitable’. Since we do not know the circumstances that led to life on Earth, it would be more realistic to assume that some random event must have occurred to initiate life, corresponding to a Poisson process [in probability theory, used to model random points in time and space]. This would suppress early emergence and thus shift the peak probability to the future.
Are we truly premature, or are we simply going to learn that life is not possible around stars in an M-dwarf habitable zone? We’ve considered all the possibilities many times in these pages. Tidally locked to its star, a planet like this would experience constant day on one side, constant night on the other, with ramifications for climate and habitability that remain controversial. Extreme radiation from solar flares in young M-dwarfs may scour the surface of life (or, on the other hand, act as an evolutionary spur). And such planets may be home to volcanic activity that can lead to runaway greenhouse effects (see A Mini-Neptune Transformation?).
In other words, life’s chances around G-class stars may be profoundly greater than around M-dwarfs, in which case the chance of life emerging does not increase as we move into the distant future. For these reasons, using our upcoming space missions to search for life around small red stars can help us place ourselves in the cosmic hierarchy. We need to learn what conditions a planet in the habitable zone of an M-dwarf can support, and the discovery of biosignatures there would cause us to re-evaluate our thoughts on ‘average’ life and its existence around Sun-like stars.
The paper is Loeb, Batista and Sloan, “Relative Likelihood for Life as a Function of Cosmic Time,” accepted for publication in Journal of Cosmology and Astroparticle Physics (preprint). A CfA news release is also available. Ben Guarino writes up Loeb’s findings in a helpful essay for the Washington Post.
A large part of the fascination of astronomy is the discovery of objects that don’t fit our standard definitions. KIC 8462852 — ‘Tabby’s Star’ — is deeply mysterious and high on my watchlist. But yesterday we also looked at CX330, a so-called FUor of the kind that brightens enormously over years of observation. Today we have another strange one, a system called AR Scorpii, where a white dwarf star in a binary system is releasing a blast of radiation onto a nearby red dwarf. The entire system brightens and fades every 1.97 minutes, a phenomenon that has only recently been properly understood.
“AR Scorpii was discovered over 40 years ago, but its true nature was not suspected until we started observing it in June 2015,” says Tom Marsh (University of Warwick), lead author of the paper on this work. “We realised we were seeing something extraordinary the more we progressed with our observations.”
Those observations proceeded with data from the European Southern Observatory’s Very Large Telescope (Chile) and the Isaac Newton Group of telescopes at La Palma (Canary Islands), along with other ground-based resources and the Hubble and Swift instruments in space. European amateur astronomers also played a key role in studying the star’s behavior.
AR Scorpii is about 380 light years from Earth. Its white dwarf component is roughly Earth-sized though containing 200,000 times the mass, and the associated red dwarf is about one-third the mass of the Sun. This is a tight system, with the two objects orbiting one another every 3.6 hours. What researchers have found is that the white dwarf is accelerating electrons almost to the speed of light in a beam that sweeps across the face of the M-dwarf. The brightening is dramatic, but the emissions range all the way from X-rays to radio wavelengths.
Image: This artist’s impression shows the strange object AR Scorpii. In this unique double star a rapidly spinning white dwarf star (right) powers electrons up to almost the speed of light. These high energy particles release blasts of radiation that lash the companion red dwarf star (left) and cause the entire system to pulse dramatically every 1.97 minutes with radiation ranging from the ultraviolet to radio. Credit: M. Garlick/University of Warwick, ESA/Hubble.
AR Scorpii was classified in the 1970s as a Delta Scuti variable, a kind of star (also known as a dwarf cepheid) that shows luminosity variations due to pulsations on the star’s surface. Such variables are useful as standard candles that help astronomers calculate stellar distances. But Marsh and team discovered that AR Scorpii’s pulsations were not the result of a single variable star but a binary system in which intense brightness variations were occurring. The pulses are strong enough that the star’s optical flux can increase by a factor of four within 30 seconds.
The nature of the AR Scorpii pulses is what intrigues the researchers. From the paper:
Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, but when in close orbits with less dense stars, white dwarfs can strip material from their companions, and the resulting mass transfer can generate atomic line and X-ray emission, as well as near- and mid-infrared radiation if the white dwarf is magnetic. However, even in binaries, white dwarfs are rarely detected at far-infrared or radio frequencies.
The team’s calculations show that the 1.97 minute brightness pulsations reflect the spin of a magnetic white dwarf, one that is slowing down on a timescale of 107 years.
Although the pulsations are driven by the white dwarf’s spin, they originate in large part from the cool star. AR Sco’s broad-band spectrum is characteristic of synchrotron radiation, requiring relativistic electrons. These must either originate from near the white dwarf or be generated in situ at the M star through direct interaction with the white dwarf’s magnetosphere.
Synchrotron radiation involves the acceleration of charged particles in a magnetic field, but as the quote above shows, what the researchers don’t yet know is the source of the electrons. The kind of pulsations observed here have been seen before in neutron stars but AR Scorpii is the first white dwarf system to show similar behavior. The paper notes that white dwarfs and neutron stars are the only two types of object that can support a misaligned magnetic dipole and spin fast enough to match the observed pulsations. The paper goes to some length to demonstrate that the AR Scorpii pulsations are consistent only with a white dwarf and not a neutron star.
The paper is Marsh et al., “A radio pulsing white dwarf binary star,” published online in Nature 27 July 2016 (abstract).
The SETI concepts now called ‘Dysonian’ are to my mind some of the most exhilarating ideas in the field. Dysonian SETI gets its name from the ‘Dyson spheres’ and ‘Dyson swarms’ analyzed by Freeman Dyson in a 1960 paper. This is a technology that an advanced civilization might use to harvest the energy of its star. You can see how this plays off Nikolai Kardashev’s classification of civilizations; Kardashev suggested that energy use is a way to describe civilizations at the broadest level. A Type II society is one that can use all the energy of its star.
In the film 2010, director Peter Hyams’ 1984 adaptation of Arthur C. Clarke’s novel 2010: Odyssey Two (Del Rey, 1982), we see an instance of this kind of technology at work, though it has nothing to do with a Dyson sphere. In the film, a dark patch appearing on Jupiter signals the onset of what Martyn Fogg has called ‘stellification,’ the conversion of a gas giant into a small star. Rapidly replicating von Neumann machines — the famous monoliths — increase Jupiter’s density enroute to triggering nuclear fusion.
A new star is born, with consequences entertainingly explored in the novel’s epilogue. Without monoliths to work with, Fogg described another way of triggering a gas giant’s fusion reaction in a 1989 paper. A small black hole could be put into orbit around the planet, its orbit gradually sinking toward the planetary center. Accretion will eventually cause the new star to shine like a red dwarf, its brightness steadily increasing over a 50 million year period. Parts of the Jovian satellite system could be rendered continuously habitable over a period of about 100 million years, even as the star-builders exploit its energies via orbiting power stations.
Image: 2010’s cinematic depiction of runaway replication in progress on Jupiter. Credit: Peter Hyams/Metro-Goldwyn-Mayer.
True, the process would one day have to be arrested, for runaway accretion will eventually, according to Fogg’s calculations, present a danger to these worlds, though presumably the civilization that can create the new star in the first place can also figure out how to tame it. These timeframes are extravagant, of course, and the engineering is far beyond our own, but as Milan ?irkovi? points out in a new paper, we should consider such stellified objects as potential SETI signatures. Dysonian SETI thus expands to a broad search for anomalous uses of energy.
Having never observed an extraterrestrial civilization, can we plausibly look for one? Here’s how ?irkovi?, the author of The Astrobiological Landscape (Cambridge University Press, 2012) and numerous papers, frames the question:
Copernicanism implies that we should reason as if humanity is a typical member of the set of all intelligent species evolved in naturalistic manner in all epochs. Therefore, what we expect in humanity’s future is also likely to occur at some point in the evolutionary trajectory of at least a significant subset of other intelligent species, both those present in the Galaxy nowadays, and those from past or future. If humans could perform an engineering feat X at some point in our future for clearly utilitarian reasons, we should expect at least some other intelligent species in the Galaxy to have already performed the same (or similar enough) X, provided they are sufficiently older from us. In accordance with such “mirroring” of human future and possible evolutionary trajectories of advanced extraterrestrial civilizations in the Galaxy, we may wish to investigate how the procedure of stellification might look from afar and consider it a new form of detection signature in the sense of SETI studies.
Notice that whatever the target, Dysonian SETI makes no assumptions about communications or contact with other civilizations. When we work at radio or optical wavelengths, we are looking for ephemeral signals, most likely some kind of a beacon that announces the existence of the culture that built it. The new Dysonian strategy puts detection times into a much deeper timeframe. We make no social or cultural assumptions and, in fact, can make no conjectures about the beings behind any artifact we find in our searches. One exciting consequence is that a SETI detection may already be present in our abundant stores of astronomical data.
The study of the anomalous star KIC 8462852 likewise touches on Dysonian SETI. While there have been brief attempts to study this object for evidence of power beaming (see SETI: No Signal Detected from KIC 8462852), the star has also been the subject of intense investigation historically, with researchers like Bradley Schaeffer and Michael Hippke reaching different conclusions about whether or not old photographic plates show a steady dimming. Here we’re using astrophysics with no cultural assumptions to delve into a phenomenon that is probably natural, but one so mysterious that we still can’t rule out advanced engineering.
But back to stellification and the question of energy. Let’s ask this: If there were a civilization capable of engineering at a solar system-wide scale, what would it do? The creation of a small star within a solar system is one way to proceed, and in Clarke’s novel it paves the way for the creation of new life on Europa. But the material for stellification is hardly confined to a single system. Usefully, we have large numbers of brown dwarfs and unbound, ‘rogue’ planets between the stars. As ?irkovi? notes, we have resources here not just for fuel but for habitation and industry with significant amounts of metals in relatively shallow gravitational wells.
The key question is, what sort of signature would this kind of stellification produce? More on this tomorrow, as we look a little deeper into Dysonian methods and speculate not only on the uses of thermonuclear fusion but the utilization of other kinds of energy. For if we’re trying to find evidence of astroengineering, extreme astrophysical sources may be the places to look.
The paper is ?irkovi?, “Stellified Planets and Brown Dwarfs as Novel Dysonian SETI Signals,” in press at JBIS. Martyn Fogg’s paper is “Stellifying Jupiter: A first step to terraforming the Galilean satellites,” JBIS 42 (1989), 587-592..
In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).
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