A bright → gamma-ray source discovered in 1973 in the
constellation → Gemini with instruments aboard NASA’s first
γ-ray satellite SAS-2.
It was known only as a γ-ray source until it was
detected in X-rays by the Einstein Observatory
and associated with an optical counterpart of apparent magnitude 25.
Because its luminosity outside of the γ-ray region is extremely
low, the nature of this object remained a mystery until the discovery
of pulsed emission, by the → ROSAT satellite in 1992, showed
that it is a → pulsar. The pulsar period (~237
milliseconds) and its → period derivative
(~1.1 × 10-14 s s-1)
correspond to a → spin-down age of ~340,000 years.
Also called PSR J0633+1746
(see Bignami & Caraveo 1996, ARA&A 34, 331 for a review).
See also: An abbreviation for the Gemini gamma ray source.
More amusingly, Geminga has been related to the Italian dialectal
ghè minga spoken by the involved astronomers. This, in Milanese,
means “it’s not there,” referring to the fact that the source could not be
detected in the radio frequencies, one of the ongoing enigmas.
