KIC 8462852: One Strange Little Star

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NASA launched the Kepler spacecraft in 2009 with the mission of finding extrasolar planets— planets orbiting other stars. Kepler did this by monitoring the brightness of nearly 150,000 stars in the general location of the constellation Cygnus. Every twenty minutes, Kepler measured the brightness of these stars to one part in a million. If any of these stars had planets with orbital planes along our line of sight, then we could see transits. A transit is an eclipse, in which the eclipsing body appears smaller than the eclipsed body. For instance, if one were situated close to the earth’s orbital plane but far from the sun, the earth would transit the sun once a year. Each transit would last about thirteen hours and would dim the sun by a little less than one part in ten thousand. As small as this dimming is, Kepler could easily measure it. Hence, Kepler has found many extrasolar planets, even ones as small as the earth.

The purpose of the Kepler mission and other searches for extrasolar planets is to find evidence that life is common in the universe. To date, these programs have found about two thousand extrasolar planets, but none are demonstrably earth-like, so these programs have failed to meet their ultimate objective.

In addition to finding transiting exoplanets, Kepler found many previously unknown variable stars.

In addition to finding transiting exoplanets, Kepler found many previously unknown variable stars. As their name suggests, variable stars are stars that vary in brightness. Some variable stars change brightness over a wide range, while others have very subtle light changes. Though many variable stars have regular periods of variation, some are irregular. The periods can be short or long. There are several ways that a star can vary. Some variable stars pulsate—they get larger and smaller, and their temperatures change throughout their cycles. The brightness of a star depends upon its size and temperature, so the brightness of a pulsating star changes over its period. Some stars vary because of many dark spots on their surfaces. These star spots probably are similar to sunspots, except that they are far larger and more numerous than spots on the sun, allowing their presence to noticeably change their overall brightness. The number of spots on stars can change, leading to variability. Additionally, as stars rotate, the amount of spot coverage that we see changes, leading to variability. Still other stars are eclipsing binaries, two stars orbiting very closely to one another. If their orbital plane is close to our line of sight, either star will eclipse the other star each orbit. This is similar to how we see transiting planets, except, owing to their much larger sizes, the stellar eclipses are much more noticeable. Finally, some variable stars are irregular, with variations probably due to random changes within the stars.

One star observed by Kepler, KIC 8462852, has gained attention in recent months. The name comes from an index number in the Kepler Input Catalog, a list of more than thirteen million targets, most of which Kepler did not actually observe. In September 2015, a group of researchers published a paper on the unusual variability of KIC 8462852. KIC 8462852 is an F-type main sequence star. Few stars of this type vary in brightness, and those that do are reasonably well understood. The variations discovered did not conform to what we know. The authors considered several scenarios that might explain the unusual behavior of KIC 8462852 and identified problems with each one. The explanation that seemed to work best was the recent break-up of a comet orbiting KIC 8462852, with orbiting fragments obscuring the star in a seemingly random manner. On January 13, 2016, Bradley Schaefer submitted a paper detailing his analysis of images of KIC 8462852 captured on archival photographs at Harvard taken over nearly a century beginning in the early 1890s. He found that during this time, KIC 8462852 gradually faded by about 20%. This sort of behavior is unprecedented in the KIC 8462852 type of star. Furthermore, it is extremely unlikely that the comet break-up hypothesis could explain this behavior.

So what is going on with KIC 8462852? In between publication of these two papers, some people seriously had suggested that this was evidence of a Dyson sphere. In 1960, the physicist and mathematician Freeman Dyson (b. 1923) was the first seriously to propose that alien civilizations could build solar-system-sized structures that we might be able to detect. Dyson published this paper three years after Sputnik, a year before the first manned space flight, and less than a decade before the first manned lunar landing. At the time, it appeared that man’s conquest of space would rapidly expand unabated. Hence, it was not difficult to envision that man might routinely travel throughout the solar system and even colonize it within a century or two. At the same time, the explosion of technology in the decades prior to publication of Dyson’s article had been accompanied by a steep increase in man’s use of energy. Extrapolating these trends into the future, it was very clear that space travel on a grand scale would require much energy, more energy than conventional sources probably could provide. Therefore, Dyson reasoned that space-faring civilizations likely would harness solar energy from platforms in space. These platforms ultimately would be linked together into structures that might be detectable by other civilizations on planets orbiting other stars.

The most drastic form of the structures that Dyson suggested was a sphere surrounding a star so that it collects all energy emanating from the star.

The most drastic form of the structures that Dyson suggested was a sphere surrounding a star so that it collects all energy emanating from the star. This would be a Dyson sphere. Since a Dyson sphere surrounds the star, the star would be invisible to us, though the Dyson sphere itself would have some temperature and hence would give off infrared energy, which we could detect. That was the point of Dyson’s original proposal—that we conceivably could detect very advanced alien civilizations by the Dyson spheres that they eventually construct. However, there are physical considerations that make Dyson spheres impractical. It is more likely that advanced alien civilization would construct Dyson swarms, collections of power-generating stations orbiting a star. While a Dyson sphere is impractical, any Dyson structure usually is called a Dyson sphere. We could detect Dyson structures several ways, including their transits of the star that they orbit. Some people have suggested that this is the proper interpretation of the KIC 8462852. Furthermore, the gradual dimming of KIC 8462852 over a century could be construed as the result of construction of a Dyson sphere during this time. However, a recent paper submitted to The Astrophysical Journal Letters described the null result of a SETI (Search for Extra Terrestrial Intelligence) radio search of KIC 8462852. It is inconceivable that a society so advanced as to construct detectable Dyson structures would be radio-silent.

Is this story of great concern to biblical creationists? Probably not. Though the Bible does not directly address the question of life elsewhere in the universe, mankind appears to be central to God’s attention. The existence of intelligent life elsewhere raises questions about God’s plan of salvation. Hence, using biblical principles, we conclude that intelligent life probably does not exist outside of earth. Even in an evolutionary worldview where the existence of life elsewhere is very important, the Dyson sphere explanation for the KIC 8462852 observations is way out there. There probably is a more mundane explanation. For instance, we have observed unexpected behavior in stars before. That sort of thing usually is attributed either to rare or even unique circumstances or to a class of objects that we have never noticed before. For instance, just because irregular variables are unknown among F-type main sequence stars does not mean that such stars do not exist—it just means that we have not yet seen one. There is no reason to think that this time it is any different.

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