TRANSCRIPT: Detecting Alien Stellar Engines

The universe can be a chaotic place where galaxies collide and stars get ejected to wander the intergalactic universe unassociated with their parent galaxy. If this situation were to happen to an inhabited star system, it might not be desirable to be ejected, or likewise if alien astronomers calculated a high likelihood that their star might be eaten by a black hole in a few million years, they might choose to construct a monumental, but hypothetically possible, megastructure that can actually move their star.

Moving a star requires a variant of the Dyson shell concept called a Shkadov drive, or class A stellar engine. It's a surprisingly straightforward idea originally put forth in 1987 by Dr. Leonid Shkadov. The idea is to build an enormous spherical mirror to reflect the radiation pressure of a star in a different direction. This would have the effect of creating thrust and would propel the star in whatever direction the alien race wished it to go. As the star moved, it would carry its planets with it just as the sun does now with our planets as it travels through the galaxy.

The problem with this idea is that the thrust would be very slight and moving a sun-like star any large distance would take millions of years so it's difficult to envision that too many of these things get built out there in the universe. But it is possible, and there is room for other scenarios where a civilization might build such a thing to move a star just a small distance if that's what they happened to need. Or, if you have a civilization that's billions of years old and very forward thinking, they might not blink an eye at projects that take millions of years to complete.

So the question is, if there are civilizations building Shkadov drives, would we be able to detect them? Just such a method was put forth in a paper, link in the description below, by Dr. Duncan Forgan of the University of Edinburgh in 2013. It's worth noting that one of the main ways we detect exoplanets is by looking at the light curves of their stars as they pass in front of it and block light.

In other words, the data needed to detect a Shkadov drive is being taken anyway in the course of finding exoplanets and studying stars. It's more a matter of someone noticing something odd in those light curves, which is how Boyajian's star was identified. Now there are issues that Forgan points out, determining if a light curve indeed indicates the presence of a Shkadov drive could be complicated by other things in the light curve, such as the presence sun spots, so much observation would be needed to confirm such a thing.

Forgan also points out that while the chances of finding a star with a Shkadov thruster are exceedingly low but with all the data that's available scientists looking for other things should be aware of strange signatures in light curves that could indicate the presence of a Shkadov drive and anyone wishing to specifically look for them could do so at low cost from already available data.

So add one more way that we might detect an alien civilization independently of radio astronomy. I think this is one of the more unlikely scenarios, I can't imagine this type of megastructure would be very common, but astronomers see all sorts of interesting things in light curves so some day in the future who knows?

Thanks for listening! I am futurist and science fiction author John Michael Godier and if you'd like to help support the channel check out my Patreon page, link in the description below, or check out my books at your favorite online book retailer and subscribe to my channel for regular, in-depth explorations into the interesting, weird and unknown aspects of this amazing universe in which we live.