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Geminga (Gemini gamma-ray source) is a neutron star approximately 552 light-years away in the constellation Gemini. Its name is both a contraction of "Gemini gamma-ray source" and the Milanese Italian dialect for "it's not there".
Pulsar
The nature of Geminga was quite unknown for 20 years after its discovery by the SAS-2 satellite. Finally, in March 1991 the ROSAT satellite detected a periodicity of 0.237 s in soft x-ray emission. Thus, it is supposed that Geminga is a sort of neutron star: the decaying core of a behemoth star that went supernova about 100,000 years ago.
This nearby explosion may be responsible for the low density of the interstellar medium in the immediate vicinity of the Solar System. This low-density area is known as the Local Bubble.
Possible planetary system
In 1997, Mattox et al. claimed to have discovered a planet orbiting Geminga by gamma-ray timing of Geminga. This hypothesized planet, Geminga b, was thought to orbit about 3.3 AU from Geminga in a 5.1 year orbit. With a mass of 1.7 earths, Geminga b would be a terrestrial planet. However, this discovery is now doubtful because recent analysis of the data indicates that the detected timing changes were due to signal noise, not a planet.
External links
- Spaceflight Now: 'Cannonball pulsar' seen flying across space
- ESA: Hipparcos pinpoints an amazing gamma-ray clock
- Extrasolar Visions: Geminga + Geminga b
Hypothetical planets | Gemini constellation | Neutron stars | Pulsars
"Geminga"