Comets probably not the answer to Tabby’s star mystery

Normally, stars dip in brightness when planets pass them, but this is definitely not what is going on with the irregular light patterns exhibited by the otherwise seemingly ordinary star KIC 8462852, also known as Tabby’s star after astronomer Tabetha S. Boyajian. Once again, the star has cast astronomers into unknown territory.

Since NASA’s Kepler telescope first sighted the abnormal light patterns, various scientists have had a crack at solving the star’s odd behaviour. On occasion, this has included losing over 20 per cent of its brightness. Up to now, the favourite explanation involves a large swarm of comets orbiting the star, while other more daring explanations venture the idea of alien megastructures like a Dyson Sphere intermittently blocking out the light.

Now, a new historical study by Bradley Schaefer of Louisiana State University has cast doubt over the comet hypothesis. By examining a Harvard University archive of digitally scanned photographic plates of the sky from 1890 to 1989, Schaefer found that the star has been dipping in light for the entirety of the period.

The data allowed him to calculate that it would take “648,000 giant comets, each with 200 km diameter, all orchestrated to pass in front of the star within the last century.” Schafer explains that this is clearly not a likely scenario.

“The comet-family idea was reasonably put forth as the best of the proposals, even while acknowledging that they all were a poor lot."

Does this mean that alien megastructures orbiting the star while sucking its energy are back on the table? While alien enthusiasts and SETI may clap their hands, Schaefer remains highly sceptical. “I too, like everyone else, would be astounded if those ideas could be proven true. But we're going for the facts”.

So as Tabby’s star cheekily continues to wink at us, the mystery is no closer to being solved. “We've got ourselves a classic mystery”, Schaefer told CNN.