An artist's concept of an "uneven ring of dust" orbiting KIC8462852. Photo: NASA/JPL-Caltech

Tabby’s Star, a far-off pinpoint of light, was discovered about a decade ago. In the ensuing years, its fluctuations of light caused some ripples of excitement in the scientific community, since some theorized that the strange patterns could be caused by a rotating alien megastructure conceived as something along the lines of a hypothetical Dyson’s Sphere, a massive contraption that could capture the star’s energy.

However, two new studies bolster the skeptics’ arguments against the theory. The papers, authored by more 200 scientists from across the globe and published on the pre-print site arXiv, present new light measurements that indicate the fluctuations from the star, KIC 8462852, that had baffled scientists for several years are instead caused by very small particles of space dust.

“Our data are inconsistent with dip models that invoke optically thick material, but rather they are in-line with predictions for an occulter consisting primarily of ordinary dust, where much of the material must be optically thin,” they write. “Ground-based follow-up observations to better characterize the star revealed nothing other than KIC 8462852 being an ordinary, main-sequence F3 star: no peculiar spectral lines, Doppler shifts indicative of orbiting companions, or signs of youth such as an infrared excess.”

The analysis of KIC 8462852 started in 2015 and continued through the end of 2017. There are four dips over the time frame, which were given the names “Elsie,” “Celeste,” “Skara Brae,” and “Angkor.” The paper focused on the “Elsie” dips, and used various tools to gauge every nuance of the fluctuating light. The methods included spectroscopy from the 3-meter Shane telescope at the Lick Observatory, as well as the Low Resolution Imaging Spectrometer on the Keck telescopes; infrared photometry employing NEOWISE observations; polarimetry using the Kast spectropolarimeter on the 3-meter Shane telescope; and even radio SETI observations from the Allen Telescope.

The dust circling the star, they concluded, was being pulled in strange patterns by the strong pull of radiation.

“The current evidence suggests that the short-term and long-term dimming are caused by dust of different sizes,” they write. “The dust concentrations that cause the short dips were created recently, and are richer in small, but short-lived, dust that is quickly ejected by radiation forces. Larger dust that is created survived and remains on a circumstellar orbit spreading from its point of origin in a manner similar to comet dust tails, causing the secular dimming.”

Tabby’s Star, named after its discoverer Tabetha Boyajian of Louisiana State University, is a dimming star about 1,480 light years away in the constellation Cygnus. (Boyajian is a co-author on both of the most recent studies, as well). KIC 8462852 first appeared to dim in 2009, at a rate of about 1 percent per week. Two years later, it dimmed 15 percent over the course of a single week – and two years after that, a flickering that lasted about 100 days. Further research found that the star had dimmed by a total of 20 percent over the last century, based on glass astronomical plates stored at Harvard University.

The alien-structure theory first was proposed in writing by a group from Penn State in October 2015. But the skepticism began almost immediately, in an Astrophysical Journal paper that was published months later by a team from Vanderbilt, Lehigh, NASA, and including an amateur astronomer from Germany. Their analysis concluded that the theoretical physics of a Dyson’s Sphere would not match the light measurements from the star. More recently, a joint NASA and Belgian team concluded back in October that an uneven dust cloud was the likely cause of the fluctuations.