I’m fascinated and puzzled by a star called KIC 8462852 some of you may already know. Scientists obviously can’t wrap their heads around its mystery, but what exactly has happened? Is it an alien megastructure or a comet supercluster? Here’s all you need to know about Tabby - astronomy’s big star that’s leaving scientists in the dark.
Going dark for decades
The star is some 1,480 light-years away, which is not unusual and it’s the Kepler space telescope’s job to find faraway planets potentially supporting life anyway. But the exciting thing is, what the telescope may have detected on top of the normal data. After starring at the stars’ particular patch of sky, waiting for each star in its range to darken by an (hopefully inhabitable) exoplanet passing in front of it, the telescope came up with more than 150,000 stars behaving as expected, and the one going by KIC 8462852 doing something absolutely weird. In order to understand the magnitude of the finding, you first need to know what ‘normal science’ expects a planet to do. Anytime a planet passes in front of a star, the star dims – just for a few hours (days at the most) and on a regular basis.
KIC 8462852 does it on pretty irregular intervals, darkening by almost 20 percent and remaining dark for at least 5 and up to 80 days. That’s absolutely unusual, causing strange light fluctuations that even the most grounded researcher can only call bizarre.
A paper published back in October of 2015 definitely ruled out faulty data and/or telescope jostling. Apparently there must be something that’s blocking the light and it is not a planet, no debris and it has not been caused by a recent collision.
A structure built by alien life
What then? As Penn Stat astronomer Jason Wright told The Atlantic afterwards: “this looked like something you would expect an alien civilization to build.” So we are talking a potential Dyson sphere (maybe a swarm, too) – meaning an ‘Alien Megastructure’ that many other astronomers have postulated to exist.
As alien civilizations become highly advanced, they’ll need more and more energy to fuel their high-tech machinery. One way could be to position solar collectors directly around a star, filling the star’s orbit until some or all of its light is blocked or creating some spherical megastructures.
Ok, Astronomers do not like to go the 'Alien Megastructure’ route that easily and went on to find out what’s really happening around a star that’s 1,480 light-years away.
The multiple comets theory
So, what else could we expect this thing to be, as after all, we’re talking about ‘something’ that’s dimming a star by almost 20 percent. If you want to put that into perspective, you only need to imagine a Jupiter-sized planet (which I’d call massive) orbiting the star, but blocking only a tiny 1 percent of its light. The scientists went on in late 2015 and at the beginning of this year, listening for any kind of radio and laser communication, but they found nothing yet. Another paper has been published since then, verifying that comets circling the star can’t be the explanation either. After looking at 1,232 photographic plates from the past century, astronomer Bradley Shaefer found that the star not only dims dramatically over short periods of time, but also that the star has been growing dimmer over time, which is a very strange phenomena and probably linked to the whole ongoing behavior.
Schaefer notes that in the past century, the star’s brightness has dipped by 16.5 to 19.3 percent, a trend “completely unprecedented”, adding that “such stars should be very stable in brightness, with evolution making for changes only on time scales of many millions of years.” He also calculated how many comets would be needed to explain such a phenomena and, you guessed it, more than we’ve ever seen revolving around such a star. Shaefer calculates you’d need 648,000 comets with a diameter of 200 kilometers (that would be 124 miles) each. The largest known comet in our solar system is only 60km in diameter. The hypothetical comets around KIC 8462852 would need to have a total mass four times the mass of everything in the Kuiper belt. “I do not see how it is possible for something like 648,000 giant comets to exist around one star, nor to have their orbits orchestrated so as to all pass in front of the star within the last century,” Shaefer writes. “So I take this century-long dimming as a strong argument against the comet-family hypothesis to explain the Kepler dips.”
This second line of data though, is only further solidifying the assumption that something weird is happening a 1,480 light-years away.
Astronomers still have no explanation what’s causing this star’s weird behavior, but at least they found a sweet name for it: Tabby’s Star. Remember, astronomer Jason Wright pointed out at the beginning that the light patterns are consistent with what we’d expect if aliens had built a Dyson swarm of solar collectors around the star, harnessing its energy. But neither Schaefer, nor Wright could prove their proposition and a new paper called Schaefer’s results into question. A study led by researchers Vanderbilt University even suggested that the centuries-long dimming may have been the direct result of differences in telescopes used to collect the data over a 90 year period. Further analysis clarifies that even the aforementioned Harvard’s plate collection underwent big changes between 1950 and 1960. The university even stopped taking many plates during that time and began anew using only one telescope. To cut a long story short Michael Lund, one of the Vanderbilt paper’s co-authors, explained that after having reviewed the light curves of KIC 8462852 and all subsequent data, only 36 giant comets could explain the star’s dimming behavior. Schaefer, though, is not confident in the Vanderbilt team’s data and countered that "they have included stars and measures that no experienced person would use”.
However, according to Tabetha Boyajian, one of the star’s discoverers and its nickname-sake, says that “even if the Harvard plates aren’t able to measure this robustly, there are a few other data sets to check out before [the long-term dimming hypothesis] is totally canned.”
A star like no other
In order to disclose the secret both amateurs and professionals have since been trained on star KIC 8462852. If comets and alien megastructure are to be ruled out, we’d first need to find definite proof that there’s no infrared energy produced.
Meanwhile a new and not yet peer-reviewed study, astronomers Ben Montet and Joshua Simon measured the light from “Tabby’s Star” that Kepler recorded during its former four-year mission. Yet again, the activity is simply strange. In its firs years, Tabby’s Star dimmed at rate of about 0.34 percent per year, only to fall off the charts by 2.5 percent in 200 days. Afterwards the original slower fade rate set in again.
After having thoroughly reviewed 500 other stars in the vicinity of Tabby’s Star, as well as 500 other stars that are similar in size and makeup to Tabby’s Star the two astronomer could say that the brightness of all the other stars remained essentially unchanged in comparison.
So none of the considered phenomena alone seems suitable enough to explain the observations and people need to combine more theories to solve the whole puzzle. Astronomers even weighed in with a theory that some sort of large and by that they mean a mega super-cloud of dust is blocking the star’s light. But a cloud also would then be responsible for extra heat energy coming from around the star, much the same as an alien structure or countless comets. Astronomers doubt there’s a new and much simpler explanation at hand, something like a stellar mechanism attributable only to this star,
The road ahead is filled with some exciting new work as scientists want to study the star while it’s in the midst of one of the major light dips, like the ones that have been witnessed back in 2011 and 2013.
A puzzle waiting to be solved
The monitoring of the star now continues using the Las Cumbres Observatory Global Telescope Network (LCOGT). Whenever there’s any sort of unusual behavior this time, a whole network of professional and amateur astronomers will be contacted immediately to collect as much data as possible. Even the European Space Agency will provide help with its PLATO telescope that astronomers already love to call “Kepler on steroids”.
Unfortunately, we all need to wait until its launch in 2024 and in the meantime can go on speculating, what’s waiting ‘round the next bend of KIC 8462852. Suffice to say, that most of us follow the events hoping for alien life and a grand ol’ mysterious megastructure right in front of Tabby’s Star.