Outer solar system is more populated than previously thought, research reveals

Survey observations using the Subaru Telescope's ultra-widefield prime focus camera have revealed that there may be a population of small bodies further out in the Kuiper Belt waiting to be discovered.

There have been five spacecraft that have flown to the outer solar system (including New Horizons), but New Horizons is the only spacecraft that has flown through the Kuiper Belt while observing Kuiper Belt objects.