  Here we describe a story behind the discovery of Kepler-46, which was the
first exoplanetary system detected and characterized from a method known as the
transit timing variations (TTVs). The TTV method relies on the gravitational
interaction between planets orbiting the same star. If transits of at least one
of the planets are detected, precise measurements of its transit times can be
used, at least in principle, to detect and characterize other non-transiting
planets in the system. Kepler-46 was the first case for which this method was
shown to work in practice. Other detections and characterizations followed
(e.g., Kepler-88). The TTV method plays an important role in addressing the
incompleteness of planetary systems detected from transits.
