If you missed the latest alien hype, here’s the gist: About a thousand light years from Earth in the direction of the Cygnus constellation, a star known as KIC 846285 is behaving in an extraordinary manner. It flashes and fades. On several occasions during our four years observing it, its light output dipped by over 20%.
It doesn’t look at all like the planetary transit events Kepler was built to detect, these will cause a star to dim periodically, by about 1% at most. As far as astronomers can tell, there’s nothing else like KIC 846285 in the Kepler database.
In a paper released on arXiv, a research team led by Tabby Boyajian proposes a number of natural explanations for the star’s light signature, including giant sunspots, epic clouds of cosmic dust, and a massive collision between two planet-sized objects. All of these scenarios are problematic for one reason or another. The most likely story is that a “family of exocomet fragments” were swept into orbit around KIC 8462582 when another star zipped close by.
Then there’s the unnatural explanation: Aliens. As astronomer Jason Wright explains in a forthcoming paper, KIC 8462852’s light pattern could be consistent with a “swarm of megastructures” built by an alien civilization to harness the star’s energy. Wright, Boyajian, and UC Berkeley SETI director Andrew Siemion are now proposing that we point a massive radio dish at the star, to hunt for the technobabble of an advanced society.
“I’m still stumped about what could be going on,” Wright told me in an email. “But something is clearly orbiting the star, and whatever they are, they are very large and have complex shapes.”
The Kepler mission was designed to stare unblinking at a fixed point in the sky, hunting for the tiny shadows of planets transiting across stars. And it’s done a beautiful job. To date, Kepler has uncovered over 4100 planetary candidates and 1000 confirmed exoplanets. Extrapolating from its small cosmic census, astronomers have reached an astounding conclusion.
“We have learned most stars have planets, that Earth sized planets are common, and a good fraction are in the habitable zone of their star,” lead Kepler investigator Bill Borucki said at an exoplanet conference. “And when you put the numbers together: 100 billion stars, 10 per cent with Earth-sized planets, 10 per cent stars like the sun, that’s a billion Earth-sized planets in the habitable zone of stars like the sun.”
The Kepler mission has literally revolutionised our view of the cosmos. Thirty years ago, we weren’t sure there were any Earth-like planets beyond our solar system, now, there could be billions. The possibility of finding life beyond Earth is no longer a pipe dream.
we’ve just scratched the surface of what this little telescope has to teach us.