Scientists believe they may have spotted an Alien Megastructure orbiting a sun in a distant solar system. Not even kidding. There is a massive object orbiting a distant star and a planet or asteroid have already been ruled out as possible explanations. Relax, no one looked into a telescope and spotted the Death Star, but from the sounds of it, this object may be just as massive. Read on as Melissa, our science guru, breaks down the facts.
Warning: It’s about to get real sciencey up in here. Yeah, Aliens are cool, but you’re going to have to learn a bit about the science we use to find them.
What is Kepler?
The Kepler Space Observatory is a spacecraft launched by NASA in 2009. It provides an opportunity to explore the galaxy for habitable planets. It does this by observing a fixed location and watching the stars’ brightness. In time, planets will sometimes orbit those stars, causing a slight dip in the brightness of the observable light. That dip can be calculated to a certain percentage, and then, based on the size of the star, the size of the planet can be determined. This is known as transit photometry.
Alien Megastructures, you say?
Recently, a very large dip was discovered on a star named KIC 8462852. This star is 1500 light years away from earth. Whereas a planet will cause a dip in the light by a percentage or two, this star had a dip of about twenty percent. Twenty percent of the light emitted from this star was blocked by something incredibly large. It would have to be about half the size of the star itself to block twenty percent of the light output. Comparatively, Jupiter, the largest planet in our solar system, is only one tenth the diameter of our sun. This star is estimated to be 1.5 times larger than the size of our sun, making it nearly impossible for the object to be a planet. Many theories have been explored and there are some very likely natural causes for the dip, yet this mystery has lead some experts to consider this to be the result of a giant alien megastructure, periodically dimming the light with its orbit.
Jason Wright, an astronomer from Penn State University, has been investigating what a huge alien construction in space might look like from Earth. He told The Atlantic: “Aliens should always be the very last hypothesis you consider, but this looked like something you would expect an alien civilization to build.”
Where is the Infrared?
Tabetha Boyajian, Yale University, led the investigations into the mysterious signals and found that the most likely natural cause was the break-up of a comet around the star. As the icy remains expand into giant clouds they could temporarily block out the light, causing the observed signal. But this should cause dust to scatter around the star, producing an excess of infrared radiation that should be easily detected from Earth. As yet, no such signal has been found. One of the main arguments against this alien megastructure theory, is that something as large as this object would be absorbing a lot of heat from the star. That heat energy would then be re-radiated and observed as Infra-Red wavelengths, and as of now no IR light has been observed from this star. This lack of Infrared is making it difficult to find the most likely explanation for the dimming event.
Despite the disadvantages of this type of method for discovering exoplanets, the main advantage of the transit method is that the size of the planet can be determined from the lightcurve. When combined with the radial-velocity method (which determines the planet’s mass) one can determine the density of the planet, and learn something about the planet’s physical structure. The transit method also makes it possible to study the atmosphere of the transiting planet. When the planet transits the star, light from the star passes through the upper atmosphere of the planet. By studying the high-resolution stellar spectrum carefully, one can detect elements present in the planet’s atmosphere.
The Plot Thickens
Since the original news hit about the strange observations made about the star KIC 8462852, from the Kepler Space Observatory, astronomers have been busy looking over data and have uncovered some new information. Bradley Schaefer, an astronomer at Louisiana State University, wanted to investigate this particular star’s dimming pattern further. He went to Harvard to look at old photographic plates of stars. There were more than 1200 photographs of KIC 8462852 to view as part of a survey collected between the years 1890 and 1989. What he found made the mysterious star even more puzzling. He confirmed that the star is flickering on short timescales, similar to the findings of the Kepler Space Observatory, but the Harvard collection also revealed that its been doing this over the course of a century.
What does this mean for the initial hypothesis? Could the break-up of comets, orbiting around the star be the answer? Schaefer calculated that it would take 648,000 stars, each 200 km wide to have passed by the star, which he was was “completely implausible.” (New Scientist)
The results also changed the requirements for the alien megastructure hypothesis. Schaefer is unconvinced that an Alien civilization would be able to build something capable of covering a fifth of a star that massive in just a century. He also reiterated the lack of infrared signal that would be required for such a structure.
Schafer added in his report that a century-long dimming like the one from the star, is completely unprecedented for any star of its size. He adds, the “century-long dimming and the day-long dips are both just extreme ends of a spectrum of timescales for unique dimming events, so by Ockham’s Razor, all this is produced by one physical mechanism. This mechanism…must be some ongoing process with continuous effects.” (Cornell)
Ockham’s Razor is a problem solving principle with philosophical origins. It basically states that the simplest explanation for something is usually the right one. Well, nothing stands out as the obvious reason for this phenomenon yet, other than the confirmation that it’s the same thing that’s caused it for over a century. Pretty awesome even if it’s still a mystery.
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Lesson Objective: Students will gain an understanding of transit photometry through the use of a hands-on web-based simulator, thus enabling them to fully comprehend the methods used by the Kepler Space Observatory.