ANALYSIS: Asteroid Forensics May Point to Alien Space Miners
It would be difficult to explain the oddball light curve that would be cause by such a intervening structure. Forgan cautions that the presence of starspots can produce "dents" in the transit light curve, as the planet crosses a starspot and this could be misinterpreted as an artificial structure. However the starspot would rotate out of view on subsequent transits. Assuming the monster-mirror is fixed in space, it's silhouette should remain stable.
NASA's Kepler space observatory has spent the last five years amassing a huge vault of planetary transit data on 150,000 stars in the constellation Cygnus. And so this hypothesis is testable.
The problem is there are many unknowns heaped upon many other unknowns. What is the probability an alien civilization has the wherewithal and audacity to try building such a monstrosity, and that it is close enough to detect?
After much speculation Forgan cautiously estimates a lower limit of one star in one million stars having such a detectable megastructure. This would put the nearest such star thruster 1,000 light-years away at best.
The Kepler database is several orders of magnitude smaller in surveyed stars. With such low chances of success it would be hard to convince anyone to fund a space observatory to go looking for alien engineering. So it will all be left as a serendipitous SETT (Search for Extraterrestrial Technology) opportunity as exoplanet surveys continue.
ANALYSIS: Do Aliens Go Invisible by ‘Going Green'?
Why would a far advanced civilization go to the budget-busting expense of doing a megastructure project to steer its star around? It's estimated that the sun has passed through 10 cold molecular hydrogen clouds laced with dust, along its galactic orbit. The consequences are that this would dim a star, and that it turn could cause some serious climate change on a planet. Long-lived aliens may want to steer around these galactic potholes.
Or the extraterrestrials might want to avoid a predicted close passage to a nearby star that might destabilize a comet cloud believe to surround planetary systems. (The approaching comet ISON is believed to be a distant visitor from this hypothesized Oort cloud around our solar system.)
There is an extraordinarily small but finite chance that evidence for such mega-engineering is buried in archival astronomy data. What's more, the absence of such evidence might suggest there is an upper limit to how far a technological civilization can progress. Or, more sobering, it means there are narrow limits on the longevity of a technological society.
Image credit: NASA, R. Villard