KIC 8462852 Tabby's Star Update 10/6/2016

This is another installment in my continuing coverage of KIC 8462852 or Tabby's star, easily the strangest star we've yet come across in our universe. Since my last update, a number of scientific papers have been published that offer a new group of potential explanations for the dimming phenomena, but the possibility of alien megastructures causing the dimming events at this star still has not been discounted.

For more solid science only back story on Tabby's star, check out the other videos on KIC 8462852 on this channel. They are arranged by date in the title, starting with the first one I did on April 10th of 2016 and together in sequence provide a complete overview of what we know and what we can reasonably speculate if indeed the dimming events at this star are of alien origin, which I stress is highly unlikely.

Most noteworthy is that there now seems to be a disparity of sorts in the story. There are two phenomena that seem to be going on at Tabby's star. The first is the major dimming events first detected by the Kepler Spacecraft that caught everyone's attention in the first place. The second, which if it exists is almost certainly related, is a long-term dimming trend first noted by Bradley Schaeffer who found that the star had dimmed significantly over the course of a century.

Schaeffer's work was called into question by a group led by Michael Hippke leading to somewhat of a public row between several scientists. Hippke essentially questioned Schaeffer's methodology and stated that he could find no evidence of this long-term dimming trend. Schaeffer had based his findings on one set of sky survey photographic plates taken over the course of a century. This wasn't the only set of plates of this kind, and Hippke used a second set known as the Sonneburg plates after the German observatory where they were taken and again found no evidence of a long-term dimming trend.

More, several other scientists published a paper calling the long-term dimming into question as well. They attributed the dimming at Tabby's Star to a gap in the data, but oddly found several other similar F-type stars in the survey that do appear to be experiencing similar long-term dimming trends of their own on a century scale. These are of unknown origin. There seems to be all sorts of mysteries buried in old sky surveys.

So is there a long-term dimming trend or not? Well, now a third group of scientists have entered the mix. Using the data from Kepler, Benjamin Montet and Joshua Simon have seemingly confirmed the long-term dimming trend over the period that Kepler was active, or at least a dimming trend during that period. So the pendulum tips in favor of the long-term dimming trend existing once more.

But that isn't the only news. Regarding the deep short-term dips that made this star famous, several new theories have emerged or reemerged regarding natural explanations that better fit the observations of this star than the previous explanations, including the alien megastructure possibility, which remains the least likely of any of the explanations but still remains on the table.

One interesting new theory was put forth by Valeri Makarov of the US Naval Observatory. This theory suggests that what we're seeing is basically some star's disembodied debris disk, perhaps tossed out into interstellar space by another gravity source, passing in front of our line of sight to Tabby's star but not actually related to it.

This seems to potentially be a good fit with what we see with the star. Such material, being in interstellar space, would be very cold. That would explain the lack of infra-red emissions that you would expect to see if the debris was orbiting KIC 8462852. It would also potentially explain both of the dimming trends, depending on how that cloud of debris was set up.

The only thing standing in the way of this explanation is weak evidence of some periodicity in the Kepler light curves. This suggests, but not very well, that whatever is causing the dimming is in orbit of the star. The only way to tell for sure is to check out Tabby's star over a long period of time to look for recurring periodic dips. The good news is that this is already happening, Tabitha Boyajian and her team have the funding and are observing the star actively. The bad news is that it could be several years before we know.  

Complicating this further are the problems with the long-term dimming trend. If it doesn't exist, then one of the older theories returns to the table, the idea that the dimming could be caused by a cloud of disintegrating comets in orbit of the star. The lack of infra-red emissions would be accounted for due to the comets being cold. But there are problems with this theory that make it not a perfect fit for what is observed.

Another group of scientists modeled the comet hypothesis. While a very large, and I mean huge, number of comets does fit with the later dimming events in the Kepler data, they could not model the day 800 long, slow, smooth event. This remains a mystery and has no easy explanation under any scenario and in some ways does serve to support the alien megastructure theory.

Another possibility is that the star is younger than we think it is and still has a disc of debris orbiting it coalescing into planets. This is also not a great fit due to the lack of infrared-emissions, but another theory suggests that if we're seeing that disc edge on, then that would account for the missing infrared.

And now to the megastructures. While highly unlikely, this is most probably a natural phenomenon, we can speculate about a few possibilities. While the Kepler light curves are consistent with a Dyson swarm, and potentially even a large baffle in space designed specifically to block light, see my earliest video for that story on that, the long-term dimming trend would suggest that we're seeing it under construction. Very rapid construction, so much so that it seems unlikely according to the Montet and Simon findings. Even self-replicating nano-technology might have trouble building something that quickly. If it is aliens, then why are they in such a hurry?

I think this speed works against the megastructure hypothesis and for the natural explanations. A passing cloud of debris could have areas of higher density that might block a star and cause a dimming trend on a scale of centuries. At some point it would go the opposite way and turn into a brightening trend. So once again, I must stress, that it is highly unlikely for multiple reasons that the mysteries of KIC 8462852 are of alien origin. But, it's still on the table. Only time will tell for sure as more observations of the star are made.