was not statistically compelling. Due to the limited angular resolution of the instrument (approximately 2.5° at 100MeV) and the small number of gamma rays detected, the exact location of the source was uncertain, constrained only to be within a relatively large "error region". At the time of detection, four weak radio sources were known within this region, two supernova remnants bordered it and a known satellite galaxy to the Milky Way lay nearby. None of these known sources were convincing associations to the gamma-ray source, and the SAS-2 team suggested that an undiscovered radio-pulsar was the most likely progenitor. Despite the investment of a significant amount of observation time, the source remained unidentified through the COS-B era; their data did, however, rule out the claimed 59 s pulsation. Many claims were made about the source during this time, but its nature remained a mystery until the identification of a candidate source by the Einstein x-ray satellite, 1E 0630+178. The characteristics of the x-ray source were unique: large x-ray to optical luminosity, no radio emission detected by the sensitive VLA instrument, point-like emission in the Einstein imager and an estimated distance of approximately 100 pc, placing it within the Galaxy. An association between the gamma-ray and x-ray sources was not conclusively made until the ROSAT x-ray imager detected a 237 ms pulsation, which was also seen in gamma rays by the EGRET instrument and retrospectively in the COS-B and SAS-2 data. Geminga thus appeared to be the first example of a radio-quiet pulsar, and served as an illustration of the difficulty of associating gamma-ray emission with objects known at other wavelengths: some characteristic of the gamma-ray source, such as periodicity or variability, must be identified in candidate counterparts at other wavelengths in order to make the connection of their identity. Finally, this principle held true when radio emissions of matching 237 ms periodicity were found at previously unsurveyed frequencies of 100 MHz and below. Proper motion The proper motion of Geminga is 178.2 mas/year which corresponds (at a distance of 250 pc) to a projected velocity of 205 kilometres per second. This velocity is very fast for a star, comparable to Barnard's Star. Timing measurements Geminga underwent a minor glitch in the late part of 1996, with a fractional change in frequency of 6.2 × 10−10. A 1998 study of the pre-glitch ephemeris suggested that the timings were being affected by