The curious case of the 'WTF Star': Why Tabby's Star still has scientists puzzled

In 2015, astronomers analyzing data collected by NASA's Kepler Space Telescope chanced upon a star that was so unusual that it would go on to baffle scientists for years. Named KIC 8462852 and also known as Tabby's Star after astrophysicist Dr. Tabetha Boyajian, this seemingly ordinary F-type main-sequence star displayed inexplicable dips in brightness that left the entire scientific community puzzled.

When exoplanets transit in front of their host star at periodic intervals, they typically block less than 1% of a star's light, and such dips in a star's brightness are expected to be observed in systems believed to have planets. But when scientists looked at KIC 8462852, they found drops in the star's brightness of up to 22% at erratic, unpredictable intervals. This, at the time, defied explanation and the star came to be informally known as the 'WTF Star', based on the discovery paper's subtitle—"Where's the Flux?".

Despite being more than 1,470 light-years away, Tabby's Star generated immense scientific intrigue and shortly after its discovery, astrophysicist Jason Wright proposed a radical theory that could explain what scientists were observing. Since the dips in brightness seemed to lack a natural explanation, Wright suggested that the irregular dips observed were mathematically consistent with that of a partial Dyson sphere, a hypothetical alien megastructure comprising a vast network of solar panels encircling a star. The theory posited that such a structure would be able to block significant portions of a star's light in asymmetrical patterns, as observed in Tabby's Star, and understandably, the hypothesis made waves, capturing public attention and prompting further scientific investigation by organizations such as Breakthrough Listen and the SETI Institute.

Attempts to find technosignatures around Tabby's Star, however, yielded no evidence, forcing scientists to rule out aliens and investigate natural phenomena that could produce the dips in brightness that were being observed. To that end, Dr. Tabetha Boyajian's team suggested that the dips in brightness could be caused by a massive swarm of icy exocomets. The theory suggested that a swarm of exocomets in proximity to Tabby's Star would fragment due to heat and leave behind a massive trail of debris, which could obscure large portions of starlight in irregular patterns. However, critics pointed out that while this theory explained short-term dips, maintaining a 22% light blockage for longer periods of time would require an improbable number of giant comets breaking apart simultaneously in tight formation, and would require too many variables to fall perfectly in place to be a viable explanation.

As investigations continued, the mystery deepened, and analysis of Kepler imagery revealed that Tabby's Star was not just dipping in brightness intermittently, but was gradually dimming overall. Over the course of Kepler's four-year run, the overall baseline flux of Tabby's Star dipped by roughly 3%, with historical reviews suggesting that a decline had been going on for years. Debris fields could not explain this persistent drop over the years, and scientists thus turned to internal stellar mechanisms to make sense of what was going on in Tabby's Star.

Something of a breakthrough came in 2017, when a network of ground-based observatories coordinated by Dr. Boyajian caught Tabby's Star dimming in real time, which provided considerable clarity. These observations showed that the star lost more light in blue wavelengths than in red or infrared wavelengths, effectively ruling out the alien megastructure theory, as any opaque object passing in front of the star would have blocked all colors of light equally. This selective blockage of light in blue wavelengths, scientists agreed, could be described by microscopic dust particles smaller than one micrometer, which are known to scatter blue light waves while allowing red light waves to pass through. And so, in 2018, a paper was published by over 200 researchers, formally eliminating the alien megastructure theory.

With dust now thought to be the primary culprit behind Tabby's Star's dips in brightness, current research on KIC 8462852 is trying to uncover how such immense dust clouds can form around older stars. In 2021, it was confirmed that Tabby's Star is part of a binary system consisting of a small, red dwarf star, and scientists think that the gravitational influence of this companion could have played a role in disrupting outer planetary bodies in the system, leading to collisions or tidal breakups. Indeed, a leading model suggests that a ringed planet or icy exomoon may have been tidally shredded by the gravity of Tabby's Star, resulting in the continuous shedding of dust sheets. Adding to this, a mid-2026 study uncovered tentative evidence of a giant planet orbiting Tabby's Star, whose gravity might be the exact mechanism pushing these fragmented bodies into the inner system. A definitive solution to the mystery, however, is not yet at hand, and modern observatories continue to monitor the star, which has become the prototype for what astronomers call anomalous dippers.