KIC 2856960, The Triple-Star System
The Kepler Space Observatory is usually busy hunting down new planets, but it spent four years of its life tracking three gravitationally bound stars collectively known as KIC 2856960. KIC was just a run-of-the-mill triplet, two little dwarf stars orbited by a third stellar body going stag. Nothing weird so far, just three stars.
For example, Kepler saw four daily dips in the light curve as the binary dwarfs crossed each other every six hours. It also saw another slight decline in the observed light every 204 days caused by the eclipsing third star.
You’d think four years’ worth of observation would be enough to get well acquainted with KIC. And so did astronomers.
But after fiddling with the numbers, the data didn’t make sense in the context of the observed behaviors of the stars. Their first job was to pin down the stellar masses. But no matter how they crunched the numbers, they failed to produce any sensible answers, even though ascertaining the mass of the stars should have been relatively straightforward.
For now, the stellar threesome has astronomers stumped. There is a potential answer that makes sense numerically yet not logically. It’s so farfetched to be almost unthinkable. The KIC system might contain a hidden fourth star. However, its orbit would have to perfectly mimic the orbit of the third star, giving the illusion of a single object.★ ★ ★