The Wilkinson Microwave Anisotropy Probe (WMAP) has observed something rather strange in our galaxy. There appears to be excess microwave radiation being emitted from the space around us, with apparently no explanation. In new research, this microwave excess may be caused by “nuggets” of dark matter, perhaps a few tonnes in mass, radiating some low energy EM waves. Could this be the first evidence of dark matter? If so, this could be a revolutionary method of observing the stuff…
WMAP was launched on June 30th 2001 to observe the background radiation that echoes around our universe. This radiation is a relic from the Big Bang which, over the last 14 billion years or so, has decreased in energy to microwave frequencies. It radiates at a background temperature of approximately 2.7 Kelvin at a wavelength of nearly 2 mm.
The WMAP mission was built to be sent to the Sun-Earth second Lagrangian point (L2), located approximately 1.5 million km from the surface of the Earth on the night-side (i.e. WMAP is constantly in the shadow of the Sun). The reason for this location is the nature of the gravitational stability in the region and the lack of electromagnetic interference from the Sun. Constantly looking out into space, WMAP scans the cosmos with its ultra sensitive microwave receiver, mapping any small variations in the background “temperature” of the universe. It can detect microwave radiation in the wavelength range of 3.3-13.6 mm (with a corresponding frequency of 90-22 GHz). Warm and cool regions of space are therefore mapped, including the radiation polarity.
WMAP has been a huge success, claiming awards for the top two scientific papers in 2003 from Science magazine. The microwave observatory continues to return amazing microwave maps of our Universe and has uncovered some strange features that have yet to be explained.
Once instrumental error and interference effects have been ruled out, WMAP picks up “anomalous” radiation coming from within our own galaxy. This isn’t restricted to the WMAP instrument either. The gamma-ray observatory, Integral has spotted a mysterious 511 KeV glow; the Compton gamma ray observatory has uncovered an unexplained signal between 1-20 MeV; even Chandra, an X-ray telescope, can see a diffuse KeV X-ray emission all over the cosmos. Now WMAP can see a “WMAP Haze” of excess GHz microwave radiation.
There is a possible answer: dark matter.
In new research published by Michael Forbes from the University of Washington (Seattle) and Ariel Zhitnitsky from the University of British Columbia (Vancouver), it is believed that clumps (or “nuggets”) of dark matter are filling the universe. Not only that, these nuggets are radiating in very low energies.
This “haze” has never been observed on Earth, as the variation in background temperature is tiny, much smaller than the interference ground-based instrumentation will receive. Space-based instrumentation can even be affected; unless they are hidden behind the Earth to shield it from the Sun. (There are calls to set up similar instrumentation on the Moon so similar observations can be carried out when facing away from the glare solar radiation.)
The researchers believe this theory will be easy to test, so hopefully a detailed campaign will commence soon. Perhaps this is the observational “evidence” needed to confirm or deny the presence of dark matter in our universe once and for all.
- arXiv Blog: Dark matter: we’ve been staring at it all along
- Original publication: WMAP Haze: Directly Observing Dark Matter?