INTEGRAL maps the Galaxy at 511 keV
Combining more than 4 years of observations, the inner Galaxy has been mapped in the 511 keV positron annihilation line with unprecedented detail as shown above using the SPI spectrometer. For the first time, positron annihilation is found to be asymmetric in the inner Galactic disk. Consistent with earlier findings, the annihilation emission is brightest around the Galactic centre. In the sky maps, the Galactic centre is at the origin and the Galactic disk runs along the equator.