From the Institute of Physics:
The latest results from the Planck space telescope have confirmed the presence of a microwave haze at the centre of the Milky Way. However, the haze appears to be more elongated than originally thought, which casts doubt over previous claims that annihilating dark matter is the cause of the emissions.
A roughly spherical haze of radiation at the heart of our galaxy was identified as far back as 2004 by the Wilkinson Microwave Anisotropy Probe (WMAP). Since then, some astrophysicists have suggested that this haze is produced by annihilating dark-matter particles.
One of the telescope’s main objectives is to accurately map fluctuations in the CMB, so it is well suited to subtracting that radiation to reveal the haze.
With the presence of the haze independently verified, focus has returned to determining its origin. After its original discovery, some researchers, including Dan Hooper of Fermilab near Chicago, US, argued that annihilating dark matter could explain the galactic haze. Dark matter has long been thought to bind galaxies together, but detecting it directly has remained elusive. In Hooper’s mechanism, dark-matter particles annihilate to produce conventional electrons and positrons. These particles then spiral around the Milky Way’s magnetic field to produce the radiation we see as the microwave haze.
However, as well as confirming its existence, Planck was also able to reveal details of the shape of the haze. “The new results seem to suggest that the haze is elongated rather than spherical [as previously thought],” explains Hooper, who was not involved in the Planck research. “Simulations suggest that we would expect to find dark-matter halos that are roughly spherically symmetric,” he adds. There might still be room for a partial dark-matter explanation, however.
It still smells like dark matter to me
Dan Hooper, Fermilab