Picture of the Month
Annihilation in the Galaxy
The SPI instrument onboard INTEGRAL has performed a search for 511 keV emission (resulting from positron-electron annihilation) all over the sky. The figure represents the results of this search: the all-sky map in galactic co-ordinates shows that 511 keV emission is - so far - only seen towards the center of our Galaxy. The SPI data are equally compatible with galactic bulge or halo distributions, the combination of a bulge and a disk component, or a combination of a number of point sources. Such distributions are expected if positrons originate either from low-mass X-ray binaries, novae, Type Ia supernovae, or possibly light dark matter.
Credits: J. Knödlseder (CESR) and SPI team
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