The European Space Agency’s orbiting gamma-ray observatory, Integral, has measured our Galaxy’s antimatter cloud, and found it to be lopsided. If confirmed, this may well play havoc with scientists who attributed the origin of the antimatter cloud to the annihilation or decay of dark matter. (It’s late and I just typed ‘dork matter’. wah. Not that we scientists are dorks or any such thing. nope.)

Anyway, scientists first discovered the emission of 511 keV gamma-rays from the center of our galaxy in the 1970s using detectors flown on balloons. This is the same energy that is released when electrons and positrons annihilate. A debate ensued between astronomers who thought the gamma-rays might be from exploding stars, and those that thought that the very roughly spherical (as measured back then) cloud would neatly overlap with the volume of dark matter at the center of our galaxy, which would be decaying and emitting electron-positron pairs, which would annihilate and produce the 511 keV gamma-rays. Only problem is, the antimatter cloud has been measured by Integral to be lopsided, which would not center on the dark matter sphere at the center of our galaxy, but could come from a population of x-ray binaries that happens to be non-uniformly distributed. Future measurements should provide illumination.

• Integral Measures Galaxy’s Antimatter Cloud