Detecting a small Kuiper Belt object using archival data of HST's Fine Guidance Sensor

The Kuiper Belt is a remnant of the primordial Solar System. Measurements of its size distribution constrain its accretion and collisional history, and the importance of material strength of Kuiper Belt objects. Small, sub-kilometer-sized, Kuiper Belt objects elude direct detection, but the signature of their occultations of background stars should be detectable. Such an occultation event lasts typically a fraction of a second, thus making it a classical high time-resolution observation. Here we report an analysis of archival data of HST’s Fine Guidance Sensors (FGS), that reveals an occultation by such a small object. The detection introduces the FGS as a valuable HTRA instrument. We discuss the statistical aspects regarding the validation of the detection claim, and its physical implications.