An alien megastructure isn’t what’s causing Tabby Star’s bizaare fluctuations in brightness. It turns out that the real reason is actually something a lot more mundane.
To dust Tabby's Star will return [Image by T. Pyle/NASA/JPL-Caltech]
A lot of us were probably hoping that there was indeed an alien megastructure around Tabby’s Star, though we also probably knew that this was an extremely unlikely scenario. Tabby’s Star, also designated as KIC 8462852, is located about 1,280 light years away from Earth in the constellation Cygnus. It was named after Tabetha Boyajian, who led the team that discovered the star’s strange dimming patterns back in 2015.
For years, there have been a number of speculations on what may be causing the unusual way that the star dramatically and abruptly dims. One particular speculation, of course, is that there is a sort of megastructure built by an alien civilization surrounding the star. Unsurprisingly, however, this is yet another space mystery that can be explained away without adding aliens into the mix.
The alien megatructure theory for Tabby's Star is out of the running.
Some scientists have guessed early on that the strange blips in Tabby’s Star’s brightness were caused by dust. It turns out that they were right. It’s not an alien megastructure, or a comet swarm, not even the debris field of a black hole located between Earth and the star—it’s just dust. It’s possible that this dust is the pulverized remains of a planet or moon that Tabby’s Star itself destroyed relatively recently.
"Dust is most likely the reason why the star's light appears to dim and brighten," said Boyajian, who’s part of the new study exploring this conclusion. "The new data shows that different colors of light are being blocked at different intensities. Therefore, whatever is passing between us and the star is not opaque, as would be expected from a planet or alien megastructure."
Thus, the nature of the findings takes possibilities like an alien megastructure clear out of the running. “If a solid, opaque object like a megastructure was passing in front of the star, it would block out light equally at all colors,” says Boyajian. “This is contrary to what we observe.”
This conclusion might seem like the most boring possible for a long-time mystery like Tabby’s Star, but it actually isn’t. There’s still a lot more to unravel, and scientists aren’t closing the book on this mysterious star.
Where did Tabby's Star's dust shroud come from?
Boyajian and her colleagues observed the star from March 2016 to December 2017 for this new study using the Las Cumbres Observatory’s ground-based telescopes. The researchers focused on four different dimming events, all of which took place during the summer of 2017.
By May of 2017, Tabby’s Star began to dim. Almost a dozen telescopes immediately swung around toward the star, with scientists diligently recording data on almost all light wavelengths. The observation period was able to cover four dips in the star’s brightness, which were all given names: Elsie, Celeste, Scara Brae and Angkor. This was something that scientists, particularly Boyajian, have been dreaming of: catching Tabby’s Star in its periodic dims in real time.
Even though scientists have taken aliens out of the equation, however, mystery still shrouds Tabby’s star. For one thing, the source of the dust itself still remains unknown.
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