Popular interest in Tabby’s Star—also known, less imaginatively, as KIC 8462852—continues as Yale astronomer Tabetha Boyjian just reached her $100,000 fundraising goal to look further into the spectral anomalies of this mysterious object. Tabby’s Star has been on the radar of alien intelligence enthusiasts ever since the discovery of anomalous and substantial (up to 20 percent) drops in its light curve. The drops were irregular and lasted between 5 and 80 days. Why the excitement? Because there’s a small—make that miniscule—chance that the dips in brightness are caused by artificial constructions built by alien civilizations.
This notion, however, is difficult to support. First, Tabby’s Star is an F-type star nearly 1,500 light years away. Main-sequence F stars are heavier than our Sun, and most have a life expectancy of less than two billion years. Here on Earth, it took more than 4.5 billion years for the first technological species (us!) to appear. Thus, any planet around KIC 8462852 would not be expected to be inhabited by complex or intelligent life.
The question remains, though: What is causing the mysterious dimming? A 20 percent dip in the light curve means that whatever object is blocking the star must be very substantial in size. (A Jupiter-size planet would cause only about a one percent drop in brightness.) The leading hypothesis is that a swarm of comets with an unusual orbit may be responsible, although it’s hard to imagine comets having such a pronounced effect. I was drawn initially to another explanation: that large pieces of planetary debris, for example from a collision, are blocking the light. But no excess of infrared light, which would be expected after such a collision, has been seen, which seems to rule out that possibility.
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