Since the Kepler space observatory launched in 2009 in search of Earth-like objects, numerous candidates have been found—each raising the tantalising possibility that they might be out there. But for the majority of Kepler's mission thus far, the most alien hunters could hope for has been the occasional star flickering in a way suggestive of the presence of far-flung, unknown worlds.
Last week, however, the Kepler mission set the world alight with claims that something had been found orbiting a star, catchily dubbed KIC 8462852, which defied most conventional explanations. And, when conventional explanations are exhausted, it seems there's one thing next thing on the list: a massive, as-yet-unknown, alien megastructure.
So, just what could be floating around KIC 8462852? We've scoured the worlds of physics, sci-fi, and far-out futurism to list some of the possibilities. So, without discounting the fact that whatever the alien megastructure is might be way beyond the realms of what our fragile human minds can comprehend, here are some of our best suggestions.
A Dyson sphere
By far the most obvious candidate out of a list of fairly far-fetched and entirely hypothetical options is that the object could be a Dyson sphere. Theoretical physicist Freeman Dyson proposed this concept in a 1960 paper in Science where he imagined a vast spherical structure encompassing a star in its entirety.
Inhabitants of the sphere would live on the inner surface enjoying permanent, uninterrupted sunlight, all the solar energy they could ever need, and horizons that, rather than gently curving downwards as they do on Earth, would rise up as far as the eye could see, before disappearing behind the sun.
A Dyson swarm
A slight variation on the Dyson Sphere, a Dyson Swarm is less a single, solid object, and more a vast, complicated array of interconnected structures spun like a web around a star – again maximising solar energy. The light signature detected around KIC 8462852 fluctuates, indicating that the star is not permanently obscured, which is perhaps more consistent with a swarm than a sphere.
To build such a thing in our own solar system could, according to an article published last year in Popular Mechanics, require the dismantling of the four inner worlds of the solar system, Venus, Mercury, Mars and, yes, the Earth. The rewards would be great however, as the energy harvested would be enough to build exciting new habitats around the sun, and give the inhabitants free, unlimited energy.
A stellar engine
Short of inverting the known laws of physics, the only way any civilisation could ever harvest the kind of energy needed for intergalactic or even trans-galactic travel, is by using a star as a kind of engine. According to the Kardashev scale—a measurement of the evolutionary level of a civilisation based upon its ability to harness energy—turning your local star into a giant engine makes you a type 2 civilisation (incidentally, given that humanity is still only capable of harvesting the energy from our home planet, we remain a type 1 civilisation).
The drawback with a stellar engine is speed. According to Leonid Mikhailovich Shkadov, one of the first thinkers to propose the idea, if our own star were used as an engine, it would take a million years to travel just 0.3 light years.
Plus, KIC 8462852 has yet to move. Then again, it should be remembered that the light we are seeing from the star has taken 1,480 years to reach us, so, for all we know, the star could be long gone by now, headed for who knows where.
An Alderson disk
The Alderson disk, named after sci-fi aficionado Dan Alderson, is a slightly less feasible version of the Dyson sphere. It works along similar lines but proposes the construction of a disk, thousands of kilometres thick, rather than a sphere. The star would reside in the middle of the disk, behind walls of ludicrous height designed to stop populations being cooked alive.
With only a small proportion of the disk being of habitable temperature however—coupled with the fact that its construction would require more raw materials than exist in our Solar System—the Alderson disk is probably an unlikely candidate for an alien home. Plus, with the sky being in a permanent state of dusk, life for its inhabitants could be a little flat.
A dystopian megacity
The manga epic Blame! imagines what a city built on a stellar scale might look like. Planning has gone out of the window and instead autonomous mechanical beings simply build the city ad hoc and in every direction. The result is a vast mechanical wilderness so large that the entire Solar System as far as Jupiter has been incorporated into its structure. And while the technology that builds the megacity is advanced, it seems to have no clear purpose, or none that is discernible to the human imagination.
For now we'll have to wait and see just what, if anything, Kepler has found nearly 1,500 light years away. With the world now turning its listening devices on KIC 8462852, we better hope that if there is an alien megastructure there, it's a friendly one.