[BRIEF NOTE] On the unknown extraordinaries of KIC 8462852

[rfmcdonald]

Yesterday I shared Ross Anderson's article at The Atlantic, "The Most Mysterious Star in Our Galaxy", because of its potential import. KIC 8462852, a star somewhat larger and brighter than the Sun 1500 light years away, hosts something in orbit.

The light pattern suggests there is a big mess of matter circling the star, in tight formation. That would be expected if the star were young. When our solar system first formed, four and a half billion years ago, a messy disk of dust and debris surrounded the sun, before gravity organized it into planets, and rings of rock and ice.

But this unusual star isn’t young. If it were young, it would be surrounded by dust that would give off extra infrared light. There doesn’t seem to be an excess of infrared light around this star.

It appears to be mature.

And yet, there is this mess of objects circling it. A mess big enough to block a substantial number of photons that would have otherwise beamed into the tube of the Kepler Space Telescope. If blind nature deposited this mess around the star, it must have done so recently. Otherwise, it would be gone by now. Gravity would have consolidated it, or it would have been sucked into the star and swallowed, after a brief fiery splash.

One speculation is that this could possibly--just possibly--be the signature of an artificial construction in orbit of the star, something like a Dyson sphere. Centauri Dreams notes that some kind of close exocomet encounter could provide a more reasonable explanation than that of an extraterrestrial civilization at work.

We’re fortunate to have four full years of Kepler data on this target, allowing the authors to explore a range of possibilities. A large-scale impact within the system is the first thing that comes to my mind. On that score, think of something on the scale of the event that caused our own Moon to form. The problem here is the time frame. The collision would have had to occur between observations from the WISE observatory and a large dip in flux (nearly 15%) seen in later Kepler observations, because we would expect such an event to trigger a strong infrared excess that was not seen by WISE. Such an excess could be there now, but this would also mean that we chanced upon an impact that occurred within a window of just a few years.

Coincidences happen, so we can’t rule that out. The paper also considers catastrophic collisions in this star’s analogue to our asteroid belt, as well as the possibility that we are seeing the passage of a disintegrating comet through the system. In this scenario, the comet would have passed well within one AU. [. . .]

But can the comet scenario explain details in the light curves of KIC 8462852? The paper notes how much remains to be explored, but concludes that a cometary explanation is the most consistent with the data. Conceivably a field star might have made its way through this system, triggering instabilities in KIC 8462852’s analogue to the Oort Cloud. There is in fact a small nearby star that whether bound to the system or not could be implicated in cometary infall.

Bad Astronomy's Phil Plait seems to represent the scientific consensus, in that an alien civilization is not impossible. Regardless, something interesting is definitely around.

I actually kinda like it. I’m not saying it’s right, mind you, just that it’s interesting. Wright isn’t some wild-eyed crackpot; he’s a professional astronomer with a solid background. As he told me when I talked to him over the phone, there’s “a need to hypothesize, but we should also approach it skeptically” (paraphrasing a tweet by another astronomer, David Grinspoon), with which I wholeheartedly agree.

Look, I think it’s pretty obvious this scenario is, um, unlikely. But hey, why not? It’s easy enough to get follow-up observations of the star to check the idea out. It’s low probability but high stakes, so probably worth a shot. And it’s not exactly science fiction; Wright and a few other astronomers have submitted a paper (pending publication) to the prestigious Astrophysical Journal examining the physics of these structures and detailing how they could be detected around other stars.

As reported in the Atlantic (which is what started all the social media interest in the first place), Wright and Boyajian are indeed proposing to use a radio telescope to look for signals from the star. An alien civilization building such a structure might leak (or broadcast!) radio waves that could be detectable from 1,500 light-years away. That’s the whole basis of SETI, the Search for Extraterrestrial Intelligence (see the movie Contact, or better yet read the book, for more on this). Telescope time is controlled by a committee, and it’s not clear if the proposal will pass or not. I hope so; it shouldn’t take too much telescope time, and under modest assumptions it shouldn’t be too hard to detect a signal.

If one exists. This is still a very, very long shot. But again, this isn’t a huge effort costing zillions of dollars. The effort is minimal, but the payoff could be pretty big. Also, radio observations of the star might prove useful in solving the mystery, even if it’s not aliens. Which, I’ll reiterate, it really likely isn’t.

I would also support follow-up observations (as indicated in the Boyajian paper) looking for signals from comets. Some molecules in comets glow quite brightly when comets get near a star, and that signal may not be too difficult to detect either. Also, there could simply be natural possibilities no one has thought of yet. More observations means stirring the pot a little more and could inspire new thinking.

The important thing is that, although Kepler had a huge sample size, the number of stars studied are only a very small percentage of the total number of stars in the galaxy. What wonders remain to be found around those?