radiation which is then amplified by magnetic stellar winds and turbulence near the galaxy's core.In 2003, the Wilkinson Microwave Anisotropy Probe found a patch of particularly energetic microwave radiation in the centre of our galaxy - dubbed the "WMAP haze". It was proposed that this could be caused by collisions of a new type of dark-matter particle.
Instead, the signal could be produced by amplified cosmic rays generated when particularly large stars explode, says Peter Biermann of the Max Planck Institute for Radioastronomy in Bonn, Germany, and colleagues.
The centre of our galaxy has a high number of massive stars compared with elsewhere. These stars are surrounded by particularly strong magnetic stellar winds. At the star's polar regions, the wind's magnetic field is parallel to the direction of travel of any escaping cosmic rays kicked out by the supernova. This configuration - plus the particularly high turbulence in the galactic centre caused by the high concentration of stars - may be increasing the energy of the cosmic rays, says the team. They have submitted the paper to The Astrophysical Journal.
Dan Hooper at the University of Chicago points out that while it's prudent to consider scenarios other than dark matter as a cause, very little is known about the inner region of our galaxy and the magnetic fields there.
0 comments:
Post a Comment