It should have been a straightforward analysis of a triple star system. The Kepler space telescope observed KIC 2856960 for four straight years, giving astronomers seemingly ample data. But when three astronomers in the United Kingdom started digging into the numbers, they discovered the system was anything but ordinary.

Tom Marsh, David Armstrong, and Phillip Carter first pulled the Kepler data from the server the night of May 21, 2012. They began by looking at signals that hinted at two small dwarf stars that were very close to each other—the smaller appeared to orbit the larger about once every 6 hours. Marsh and team called this the binary. Then there appeared to be a third, the triple, which orbited every 204 days. Other astronomers who had studied the system had come to this conclusion, too.

But then Marsh and colleagues started digging deeper. When sifting through the light curve data—the intensity of light over time as recorded by Kepler—they noted periodic dips in intensity. This isn’t unusual in multiple-star systems. Light from one star will dim or change if an orbiting body passes between it and the telescope.

The dips, however, didn’t match with their other calculations. The team felt confident in their understanding of the fast-orbiting, dwarf-star binary, but the appearance of the dip every 204 days was throwing off their results. Based on the dips in the light curves, they couldn’t arrive at realistic stellar masses.