In the classic 1937 sci-fi novel "Star Maker," author Olaf Stapledon imagined a massive machine that could encompass an entire star, capturing its energy and harnessing it to provide near unlimited energy to space-faring civilizations. More than two decades later, Stapledon's creative thought experiment became a legitimate scientific concept when physicist Freeman Dyson published a 1960 paper in the journal Science. Dyson argued that, logically speaking, any sufficiently advanced extraterrestrial civilization would develop such intense energy needs that they would need megastructures like those envisioned by Stapledon.
Thus the concept of Dyson spheres was born, but they've remained theoretical — until perhaps recently. A study last month in the journal Monthly Notices of the Royal Astronomical Society using observations from star-observing programs Gaia , 2MASS and WISE suggests that Dyson spheres may exist around at least seven different stars.
The scientists say this is so because they discovered infrared heat signatures near these stars — all within 1,000 light year of Earth — that cannot otherwise be explained yet. Other experts, however, are not so sure. Barnard College theoretical cosmologist Dr. Janna Levin is among them, having publicly suggested that the heat signatures could be explained by factors like planetary collisions, a very young star with material spinning around it in a disk or a distant galaxy behind some of the stars. Those are not her only reservations.
"Dyson spheres are more likely to be Dyson swarms — a vast collection of solar-energy collecting satellites, each on independent orbits around the Sun," Levin told Salon. "Any instrument that collects energy wastes some in the form of heat. It’s the heat signature that scientists have recently searched for. Heat signatures are so generic in nature that it’s far from a smoking gun and there are many possible natural explanations."
Astrophysicist and science writer Dr. Ethan Siegel told Salon that although stars emit very large amounts of energy, the temperature at which they radiate is determined by the size of the surface area from which the energy is emitted.
"The larger the surface, the lower the temperature," Siegel said. "So if you find a star emitting a large amount of energy but at a very low temperature, it makes sense to conclude that there's either the star is very large and 'puffy,' or perhaps there's an external structure around the star that's radiating heat outward after absorbing the solar energy."
Perhaps unsurprisingly, Siegel is skeptical that the seven stars identified in the new paper are actually surrounded by Dyson spheres.
"My personal view is that, out of the nearly ~2 billion stars that Gaia has catalogued, there was an explicit search for, 'Which objects are most consistent with the idea of this being a Dyson sphere?'" Siegel said. "And these were the seven best candidates. None of them are particularly compelling — it's just saying that if Dyson spheres are out there and have been built, could we find them and what is the best match, observationally, for that scenario."
He added, "Alternatively, it could just be normal old astrophysics at play, with no aliens, no megastructures, no Dyson spheres, and nothing exotic. When you have an extraordinary explanation and a mundane explanation for the same observed phenomenon, you really need more (extraordinary) evidence to favor the former explanation over the latter one, and we don't have that."
Dr. Erik Zackrisson. an associate professor in astronomy at Uppsala University and one of the study co-authors, explained to Salon that all scientists know for sure is that these seven stars possess excess infrared radiation and that the properties of said radiation are consistent with what we would expect from Dyson spheres. That, however, does not mean that they are Dyson spheres.
"They are the best Dyson sphere candidates we've come across so far, but this does not mean that they are Dyson spheres, or even that Dyson spheres represent the most likely explanation for the phenomenon we're seeing," Siegel said. "Dust around a newborn star, a chance alignment with an infrared-bright background object, or dust due to some sort of rare cosmic catastrophe in the planetary systems of these stars (colliding planets or something similar) may also constitute viable explanations. "
Like the other experts who spoke with Salon, Zackrisson was very skeptical that the most inspiring and fantastical outcome — that these heat signatures are proof of intelligent extraterrestrial life — will be how things turn out.
"Personally, I think these objects are very unlikely to be Dyson spheres," Zackrisson said. "Some of them have already been argued to be due to chance alignments with background sources. Such cases are astrophysically uninteresting, so my hope is that at least some of these sources will be confirmed to have intrinsic infrared excess fluxes — then we're at least onto something interesting, even if it eventually boils down to extreme astrophysics rather than aliens."
Even though the experts agreed that these are not likely to be Dyson spheres, Levin still believes the recent study has scientific value.
"I think a fascinating twist would be to consider that we have a swarm of satellites around our own Sun and they must emit some heat," Levin said. "Is someone looking at us wondering if they’ve found signatures of intelligent life? Fascinating. However, we’ve not been at this space industry for very long and so an alien civilization observing at us would have to be very nearby, within 50 light years. And even then, the signs would be too faint."
She added, "What could be more exciting and existentially terrifying than the discovery of alien life?"
Siegel echoed that observation.
"It's important to keep an open mind, and it's easy to understand why the most wild possibilities excite us," Siegel said. "But without stronger evidence, this is just another example of people getting hyped up over what's almost certainly going to be a big nothing-burger."
