As we saw yesterday, the Infrared Astronomical Satellite (IRAS) has been the source of data for a number of searches for unusual infrared signatures. The idea is to look for the artifacts of advanced extraterrestrial civilizations, under the assumption that a sufficiently advanced culture will be capable of engineering projects that could be detected from light years away. A Dyson sphere, existing either as a completely enclosed star or as a swarm of artifacts around a star, is but one example of such engineering, but its a sensible one to look for because it represents a way to maximize energy. Its also theoretically detectable because of waste heat in the infrared.
These days, though, we have not just IRAS but the Wide-field Infrared Survey Explorer (WISE) and the Spitzer space telescope providing us with infrared data. Richard Carrigans pioneering work on interstellar archaeology is now complemented by searches funded by the New Frontiers in Astronomy & Cosmology program, set up by the Templeton Foundation and administered by the University of Chicago. The program has been created to provide grants in areas ranging from our universes role in a possible multiverse to the detection of intelligence beyond our Solar System. The team of Jason Wright (Pennsylvania State) and colleagues Steinn Sigurðsson and Matthew Povich is one of three grant winners in a tuned up Dyson artifact hunt.
As described by Stephen Battersby in Alien Megaprojects: The Hunt Has Begun, a recent article in New Scientist, this search should be able to expand Carrigans observations thousands of times farther, with the ability to detect a Dyson sphere around a Sun-like star almost anywhere in the galaxy. And this gets us into interesting terrain. From the article:
Even such a wide-ranging hunt may not be ambitious enough, according to Wright. He suspects that interstellar travel will prove no harder than constructing a sphere. An alien civilisation with such a high level of technology would spread out and colonise the galaxy in a few million years, building spheres as they go. I would argue that its very hard for a spacefaring civilisation to die out. There are too many lifeboats, says Wright. Once you have self-sufficient colonies, you will take over the galaxy you cant even try to stop it because you cant coordinate the actions of the colonies.
A good point. And if this is the case, we would expect to find Dyson spheres, assuming were correct in thinking they represent a reasonable way to maximize the collection of energy. To find one or a few Dyson spheres in our galaxy, Wright goes on, would be very strange. In other words, there are either going to be a lot of them or none at all, and if there are a lot of them, then we might consider taking the hunt into extra-galactic territory. Wright tells Battersby that a galaxy colonized by a Kardashev Type III civilization should show up as a big, bright object in the infrared data from WISE, clearly flagged by virtue of the fact that it has no optical component.
How likely is it that things like Dyson spheres will ever be built? Wright has written about this on his AstroWright site, from which this quote:
despite all of the advances in medicine, economics, and civilization generally, we are still growing as a species exponentially. We have long left Malthusian limits behind, and have shown that technology will progress faster than our resource demands. But no technology can give us more energy than hits the Earth until we start talking about spaceships (except for nuclear energy, which is an ultimately finite resource; fossil fuels are, ultimately, just stored energy from sunlight that hit plants millions of years ago, so, again, finite). We will continue to grow as a species until we hit a free energy resource limit, and then in order to further grow we will have to start collecting more solar energy. And we will have to start emitting that energy as waste heat. And that trend, too, will then have to proceed exponentially
The consequences are interesting to contemplate.
Indeed. The approach is speculative and obviously depends on how an advanced civilization builds its energy collectors. Dyson spheres are one thing, but a thin ring of artifacts around a distant star is not going to be easily flagged even in the WISE data. A second survey, this one with a different approach, is in the hands of Princetons Lucianne Walkowicz, who with her four co-investigators will be looking through Kepler data for unusual patterns of variability. Here were in familiar territory with the analysis of light curves that has proven so productive in detecting exoplanets.
Will Walkowicz team find something spectacular? After all, their proposal is titled Stellar Lighthouses: Decoding Signatures of Advanced Civilizations in Precision Stellar Photometry, and any signature of something artificial around a distant star is going to change everything. But this is a search for more than Dyson spheres, just as interstellar archaeology comprehends much more than a single postulated technology.
Suppose a distant civilization is using microwave beaming to drive spacecraft, or modifying its stars makeup to prolong its life? Steinn Sigurðsson, blogging from the New Frontiers in Astronomy & Cosmology conference in 2012, recalled an old Analog story about the discovery of unusual stars, so bizarre that they demand immediate investigation. One turns out to have a convective zone spiked with manganese and one is bright green. The conclusion is that extraterrestrial pranksters are spiking the stars to draw attention. Who knows what may turn up, but as Walkowicz tells Battersby: We know what transits, starspots and flares looks like, so we are looking for any variation we cant explain through known astrophysics.
Geoff Marcy (UC-Berkeley) is also in the hunt, working with the University of Hawaii at Honolulus Andrew Howard and John Johnson (Caltech) on the same kind of signal via Kepler data. The data, of course, are already in our possession, though we keep adding to the database. But its a fascinating speculation that we may already have detected signs of an extraterrestrial civilization without even realizing it. The hunt for astronomical anomalies means combing through vast amounts of data with a clear view of our own preconceptions and how they might mislead us. Marcys team will doubtless find unusual variability in a number of objects that can be explained through conventional means, but finding the inexplicable will get everyones attention.