But attract attention it has. The star with its weird behavior has not only captured the imagination of professional astronomers determined to solve the puzzle, but has also gained notoriety in the eyes of the public. The star found fame—from Saturday Night Live to Late Night with Stephen Colbert—because of a suggestion by astronomers (alright, we admit it was us) that radio astronomers partaking in the search for extraterrestrial intelligence (SETI) should point their telescopes that way.
SETI astronomers have long suggested that advanced alien civilizations might construct planet-sized “megastructures” to harvest massive amounts of starlight. Such objects might be detected when they happened to pass between Earth and the star and might resemble similar signatures caused by natural objects.
Meanwhile, astronomers continued to study the star for signs that its strange eclipses could have an easily explainable natural cause. Boyajian postulated that the eclipses might be caused by a family of comets around the star. While it is still the best among many contrived explanations, comets cannot explain each and every event observed by Kepler. The search for a more convincing natural explanation remains ongoing.
In October 2015, shortly after the alien megastructure hypothesis went public, Bradley Schaefer, an astronomer specializing in careful stellar brightness measurements, decided to look for previous episodes of odd behavior by examining a historical astronomical treasure: photographs of the sky stored in the plate stacks at the Harvard Astronomical Plate Collection in Cambridge, Massachusetts.
For about 100 years, small telescopes have imaged the entire sky, bit by bit, on photographic plates. These plates are now carefully archived and stored by curators at the Harvard-Smithsonian Center for Astrophysics. The center has slowly digitized and made the plates available to the public through a program known as Digital Access to a Sky Century @ Harvard (DASCH).
Schaefer constructed a historical record of Boyajian’s star using online DASCH data. While Schaefer found no evidence of obvious prior eclipse events, the DASCH data did seem to show that the star had slowly dimmed by nearly 20 percent over the past 100 years.
Intrigued, but aware of the numerous systematic errors that plague photographic plate astronomy, Schaefer visited the plate stacks in Cambridge and repeated the measurements in person. His conclusion remained unchanged and unprecedented: No other star had shown such dimming before, and no natural explanation seemed forthcoming. This provided the first evidence beyond the Kepler data that something strange was going on with the star.
But other astronomers were skeptical of Schaefer’s claim. Two teams began simultaneous efforts to verify Schaefer’s surprising result with their own analyses of the DASCH data. One team was a collaboration between German amateur astronomer Michael Hippke and NASA Postdoctoral Fellow Daniel Angerhausen, and the other a team of professional astronomers from Vanderbilt University and Lehigh University lead by doctoral student Michael Lund.