Although it’s some 1,480 light-years away from Earth, the mystery known as “Tabby’s Star” has captured the attention of professional and amateur stargazers alike, sparking fantastical speculation about what might explain its erratic light-curve. Some astronomers have gone so far as to suggest that the star’s bizarre flickering and dimming could result from shadows cast by an alien megastructure—perhaps a fleet of solar collectors constructed by a more advanced civilization within the faraway constellation Cygnus.
The star gets its “Tabby” nickname from Yale astronomer Tabetha Boyajian, and its other even more whimsical nickname, the “WTF Star,” from an immensely popular paper she wrote about it called “Where’s the Flux.” Last but not least, the star is also known by the scientific moniker “KIC 8462852.” Whatever it’s called, it has enchanted amateur planet hunters. Simply put, there is a lot of something in orbit around the star. Which raises the possibility that the “something” is evidence of ETs.
But the head of UC Berkeley’s prestigious Search for Extraterrestrial Intelligence (SETI) research program isn’t buying it.
“The most likely explanation is an astrophysical one,” says Andrew Siemion, director of SETI and the Berkeley lead on the Breakthrough Listen initiative—the ambitious international program to spend $100 million over 10 years to cover 10 times more of the sky and examine a million of our closest stars. It’s billed as the biggest scientific search ever undertaken for signs of intelligent life beyond Earth, and its tasks for the Berkeley research program include investigating the possibilities with the WTF Star.
“The drunk has to look for his keys under the lamppost,” Siemion says with a smile. “That’s the starting point.”
The “drunkard’s search” is an old joke turned parable that Siemion uses to help explain a common observational bias.
A policeman sees a drunken man searching for something under a streetlight.
Policeman: Hey, what are you looking for?
Drunk: I lost my keys.
They both look under the streetlight together. After a few minutes the policeman stops.
Policeman: Are you sure you lost them here?
Drunk: No, I lost them in the park.
Policeman: Then, why are we looking here?
Drunk: This is where the light is.
The “streetlight effect” is a cautionary principle in science that states we are only able to search where we are able to see. It’s particularly applicable in radio astronomy because our methods of detection and data collection are limited by technology. When looking to see whether alien life is really out there, the anomalies of the WTF Star do seem to offer an excellent place to start looking, but more than likely it isn’t the best place to look.
The “light-curve,” the star’s signature light output, shows a large amount of orbiting matter blocking the star at irregular intervals. This would not be an unusual occurrence for a young star, as debris in its solar system would still be coming together or ejecting from orbit, but based on the temperature data, this star is mature and should not have an abundance of chaotic orbiting matter. Things should have settled down already.
So what has caused the irregular dimming of the star?
To begin the process of elimination, astronomers needed to rule out instrument error in the observations—a process known as data reduction analysis. The data for WTF has been checked and rechecked, and the calculations confirmed. That led to raised eyebrows in the astronomy world and fueled speculation about alien involvement.
The next working theory suggested that a host of comets were recently swept into the WTF system by the mass of a passing star. But analysis of archived data from Harvard undercut the comet theory. The data goes back to 1890 and indicates that in the past 100 years, an incredibly short time in the life of a star, the light output has dimmed a staggering 20 percent overall. New calculations for the comet theory suggested that it would require 648,000 comets, 200 kilometers wide, orbiting in a precise fashion. In short, also unlikely.
But archived observational data can be misleading, and the bizarre fluctuations may still simply be within the margins of error.
“Clearly there’s something weird going on with the star,” says Siemion, “It’s probably not just comets. If a star spins very fast the edges can get suspended, creating hot spots. If something passes in front of it in long-term orbit, it can create these asymmetric light-curves. That particular result doesn’t rule out anything.”
In October, the nonprofit SETI Institute in Mountain View used the Allen Telescope Array to explore the mystery of WTF, searching in vain to detect artificial radio signals. More recently, Iowa State astronomers who had assessed the star using data taken with the Infrared Array Camera of NASA’s Spitzer Space Telescope reported that the lack of strong infared excess “disfavors” several other possible scenarios, including a catastrophic collision in an asteroid belt, a giant impact to a planet in the system, or a population of dust-enshrouded planetesimals. Instead the authors concluded that the “preferred explanation” is that the dimming in the light curve was due to “the destruction of a family of comets….”
An excess of infrared radiation also might have indicated that the WTF Star might be surrounded by an orbiting structure of artificial design, which would be emitting additional radiation beyond what the star itself generates. Among astronomers, this is a popular prediction about how humans will first identify signs of alien life. The premise: Engaging in advanced engineering projects, such as space travel, or even time travel back to Egypt, would require huge amounts of energy. That energy source could be a gigantic stellar energy–collecting apparatus, a megastructure of solar panels around a star—a design called a “Dyson Swarm.” But SETI observations failed to turn up any sign that WTF was emitting such telltale excess radiation.
Of course it’s quite possible that distant civilizations have developed different energy needs altogether, explains Siemion, and that our own projection scenarios may be limited by our conventional ideas. As our technology expands and distant galaxies come into focus, our solitude in the universe grows.
And that, in its own way, is equally unsettling.
“If we don’t discover life out there in the next few hundred years,” he says, “we have to start asking ourselves, why here?”