Picture of the Month 

January 2004


Positron-Electron Annihilation in the central region of our Galaxy

Positron-Electron Annihilation in the Galaxy

The annihilation of positrons with electrons in the central region of our Galaxy results in gamma-ray line emission at 511 keV - the rest energy of the annihilated particles. The observation of the line in 2003 shows the ability of the SPI instrument to detect gamma-ray lines even with modest exposures. This opens up exciting possibility for more detailed studies of this line, since especially the Galactic Center will be observed by INTEGRAL for much longer (e.g. as part of the Galactic Center Deep Exposure).

The spectrum shown is based on data from INTEGRAL Science Working Team (ISWT) Core Programme data, spectra and maps for different parts of the Galactic plane will be derived by different ISWT research groups; here we show data from the SPI Team.

Courtesy: the SPI team

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