You can put away your Men in Black suit for now: There's new evidence the "alien megastructure" that made headlines last year doesn't exist.
In October, astronomers discovered a star called KIC 8462852 that captured international attention for its strange behavior, namely how the star's brightness dimmed by up to 22% over 100 days of observation.
This puzzled scientists because when a planet passes in front of a star, it only dims the star's brightness by about 1%, according to Science Alert.
Which meant something else was blocking out the star's light.
The researchers who discovered the star couldn't rule out the idea that the dimming was caused by a giant alien megastructure like a Dyson sphere orbiting around the star.
Now scientists have identified another star, called EPIC 204278916, that exhibits some of the same strange dimming behavior we see around KIC 8462852.
According to the research describing EPIC 204278916, the star's brightness dipped up to 65% over 25 days. The researchers have proposed a non-alien explanation that might also apply to the dimming we see around KIC 8462852.
So what's causing the strange behavior of these stars?
Originally, astronomers proposed that KIC 8462852's dimming might be caused by a field of comet debris passing in front of the star. And later, some hypothesized that the star was spinning so fast that it stretched out, causing the poles to brighten and the center to darken.
The problem is that both of these explanations don't quite fit the star's dimming pattern. Now the discovery of EPIC 204278916 has introduced a new (and non-alien) explanation. The researchers have published a preprint version of the study suggesting the star might be surrounded by a giant disk of gas and dust. If the disk is lined up with the star just right, it could be causing the dimming that we see.
KIC 8462852 could also have a giant disk of gas and dust around it, according to a blog post from Ethan Siegel at Forbes.
"If this star turns out to be younger than is generally accepted (which many professional observers think it is), if it has a disk that happens to be edge-on (so we don't see the infrared flux), and if there's either a warped inner disk or cometary-like debris, then what we've discovered is a new stage in the early evolution of a class of stars!" Siegel wrote.
It will take a lot more research and observation to determine if this is what's going on, but it's a more likely explanation than aliens. Researchers have raised enough money to study KIC 8462852 for a full year, so we might have some answers soon.