The ‘Alien Megastructure’ Star Is Dimming Again

Astronomers all over the world are rushing to train their telescopes on it.


The most mysterious star in the Milky Way is at it again.

Astronomers are sounding the alarms Friday as telescope observations detect unusual light patterns coming from a distant star located about 1,300 light-years away from Earth in the constellation of Cygnus, in the outer edges of the galaxy. The mysterious dimming and flickering of the star, first discovered in 2011, means something is passing in front of it. It has puzzled astronomers ever since, but this is the first time they’ve seen it dimming in real time, presenting an extraordinary opportunity to observe whatever it is that’s blocking the star’s light.

So it’s quite understandable that they’re kind of, well, losing it on Twitter right now:

Tabetha Boyajian, an astronomer at the Louisiana State University, and Jason Wright, an astronomer at Penn State University, are among the scientists working on solving the mystery of KIC 8462852, sometimes nicknamed Tabby’s Star for Boyajian. The first observations of the star came from the Kepler Space Telescope, which has been tracking the brightness of stars since 2009, looking for small dips in their light—hints that an exoplanet or two (or seven) may be lurking. Astronomers made Kepler data available to the public through a program called Planet Hunters, encouraging “citizen scientists” to join in the search for exoplanets. In 2011, a group of volunteers noticed strange light patterns coming from KIC 8462852. They hadn’t seen anything like it in the 150,000 stars Kepler had observed.

Astronomers still don’t know what is causing this dimming behavior, which was first reported by The Atlantic last year. The brightness of the star has been observed dropping by more than 20 percent, a significant change that suggested something massive must be orbiting around it.

There are several possible interpretations involving natural, cosmic phenomena, like a buildup of debris from an impact or nearby asteroids. But, as my colleague Ross Andersen previously reported, this explanation would only make sense if the star were young, and it’s not. In the early stages of a solar system, including our own, disks of dust hang around the parent star before eventually being swallowed or shaped by gravity into planets. Such dust would emit detectable infrared radiation. Astronomers haven’t observed that around KIC 8462852, suggesting it may be too old for this hypothesis.

Another explanation involves—you guessed it—aliens. To Wright and his colleagues, the irregular light patterns could suggest a collection of megastructures are orbiting the star, technological artifacts built by an advanced, spacefaring civilization. This time around, astronomers will be able to take “spectra” from the dimming star, which will tell them what kind of material the orbiting objects are made of. It’s possible the data could indicate material of a technological origin.

Wright said Friday that astronomers will have spectra data from some observatories ready to analyze by Saturday morning. “I don’t think we’ll solve this puzzle this weekend,” he said during a live YouTube discussion about the news, but they’ll have some of the information they need to start.

Astronomers are eager to throw as much observation time at Tabby’s Star as possible, and several telescopes around the world regularly track it. Astronomers began to notice something might be coming in the telescope data earlier this week, according to Wright. A telescope in the Canary Islands failed Thursday night, and astronomers were forced to wait 10 hours before useful data came through from another one in Arizona. Here’s what the start of the dimming looks like:

The detection doesn’t look like much in a plain chart on Twitter, but—trust the astronomers—it’s big.