On Tuesday, October 13, 2015 Ross Anderson’s article, The Most Mysterious Star in Our Galaxy was published at the Atlantic. The story was then picked up by Popular Science the same day and summarized in an article there. Since then, additional discussion has appeared on Centauri Dreams, and Phil Plait on Slate in his Bad Astronomy column has also commented on it.
It is all based on a paper that appeared on Arxiv.org that discusses the star KIC 8462852, located 1480 light-years away, one of the 150,000 starts studied by the Kepler space probe that searched for planets around other stars and wound up detecting several thousand. But KIC 8462852 stands out in its weirdness.
Kepler discovers planets around other stars by watching the brightness of the light coming from the stars. If a planet happens to pass in front of it, the star’s light will dim just a bit, for a few hours, or maybe a few days. For instance, if aliens had a Kepler aimed at us, they’d notice the Earth when our sun dimmed slightly every 365 days, by a fraction of a percent; in fact, it takes very, very sensitive instruments (which Kepler has) to detect such minor drops in starlight that a planet would cause. And by using this method, Kepler has discovered thousands of planets around other stars.
KIC 8462852 darkens by as much as 80 percent and it stays dark for anywhere from five to eighty days. According to the Atlantic, the researchers who notice this call it “bizarre.”
The paper posits several possible explanations for this unique behavior (something that has never been seen with any other star, ever). The obvious first possibility is that it is due to some problem with the instruments or the data. Another possibility is that the star is simple a variable star. Even our own sun varies in its output of energy over an eleven-year cycle. Perhaps it’s a clouds of dust around the star that are periodically dimming it from our perspective, or maybe a swarm of comets or debris from a couple of planets that collided. The paper discusses these and other possibilities and finds all the explanations wanting. And that’s as far as the paper itself goes with it, though the paper suggests that the comet idea is the most promising hypothesis.
But the researchers involved have thought of another possibility that they did not include in the paper, but that they are running some experiments on to see if it could be true. Popular Science put it this way:
“[Jason] Wright, and many other astronomers, have postulated that we could detect advanced civilizations through their technology. The idea is that as alien civilizations become highly advanced, they'll need more and more energy to fuel their high-tech lifestyles. Perhaps the aliens would position solar collectors directly around a star, filling the star's orbit until some or all of its light is blocked. These hypothetical alien megastructures are called Dyson swarms or spheres.”
As Phil Plait points out, the odds are that some natural explanation for the peculiarity about this star will come to light eventually. The researchers involved argue that aliens should always be your last explanation for anything weird, of course.
Still, it remains intriguing; and whatever is going on, it’s something new we haven’t come across before.
If it is aliens, it won’t immediately change much, of course. They would be 1480 light years away, so we’re looking at the way things were around that star 1480 years ago, around the time Islam was first on the rise, and not so long after the collapse of the western half of the Roman Empire. These aliens have no way of knowing that we exist, since back then we were producing no radio or television signals. And it’s improbable that the civilization that produced the Dyson swarm would still exist; most civilizations on Earth have endured but a fraction of that sort of time span; certainly our world is nothing like what it was 1480 years ago.
So unless we develop warp drive, we’ll never carry on a conversation with them and what we know of them will be extremely limited by the distance. But at least we’ll know that humanity is not the only intelligent species in the universe.