For decades, the search for intelligent extraterrestrial life has used giant radio telescopes on the ground to scan the skies, hoping to detect alien broadcasts from somewhere in the Milky Way. (No luck so far.) But the rise of powerful space telescopes capable of observing hundreds of Earth-like planets orbiting distant stars, like the Kepler telescope launched in 2009, changed the game. The right technology, astronomers say, could someday allow humans to see optical evidence of extraterrestrial life.
So, what can astronomers look for? The most popular suggestions are structures built by civilizations, far more advanced than our own. In 1960, Freeman Dyson hypothesized spheres or swarms constructed to harness and harvest the energy of a parent star. In 2005, Luc Arnold proposed artificial objects inserted into a planet’s orbit to serve as a signal of existence to other civilizations. Now, a pair of astronomers suggest looking for shields constructed to protect against deadly cosmic explosions.
Milan Cirkovic and Branislav Vukotic suggest, in a report published this month in the journal Acta Astronautica, that advanced civilizations could lasso objects within their solar system to engineer shields that would dampen the dangerous effects of exploding stars or gamma-ray bursts. After all, no one wants to be wiped out by a supernova—and a sophisticated, space-faring society with enough technological prowess could actually do something to protect itself. Back on Earth, telescopes like Kepler could spot these shields as they transit their stars, creating the dimming effect the spacecraft is built to observe. Powerful infrared telescopes could also detect the shields by the heat they emit.