Geminga /ɡəˈmɪŋɡə/ is a gamma ray and x-ray pulsar source thought to be a neutron star approximately 250 parsecs[1] (around 800 light-years) from the Sun in the constellation Gemini.

Its name, attributed by its discoverer Giovanni Bignami, is both a contraction of Gemini gamma-ray source, and a transcription of the words ghè minga (pronounced [ɡɛ ˈmĩːɡa]), meaning "it's not there" in the Milanese dialect of Lombard.

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.

[11] 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.

Finally, this principle held true when radio emissions of matching 237 ms periodicity were found at previously unsurveyed frequencies of 100 MHz and below.