London, September 10 : Astrophysicists are debating whether the mysterious dark matter is a WIMP (Weakly interacting massive particle), or a CHAMP (Charged massive particle).
According to a report in New Scientist, the mysterious dark matter that makes up most of the material in the universe may actually have an electric charge, a new study suggested. If so, it might help explain why astronomers see so few dwarf galaxies in orbit around larger ones.
Dark matter is detected by its tug on light and visible matter, so astrophysicists have largely assumed that it interacts mostly through the force of gravity - and not electromagnetism, for example.
Indeed, the leading dark matter candidates, known as weakly interacting massive particles, or WIMPs, are electrically neutral.
But theorists Leonid Chuzhoy and Rocky Kolb of the University of Chicago have said that it may be time to consider the possibility that dark matter is actually composed of charged massive particles, or CHAMPs.
That would mean magnetic fields could push on or deflect dark matter - adding another way for it to interact with the known universe.
The idea for CHAMPs is not new. It was actually discarded more than a decade ago, after underground particle detectors failed to pick up any sign of such candidates.
Now, a new analysis has suggested that the particles may exist - just not in our galactic neighbourhood. That's because the shape of the Milky Way's magnetic field could prevent CHAMPs from entering the galaxy's disc of stars, where the Earth resides.
Any CHAMPs in the disc would have been cast out long ago, slingshotted outwards by the magnetic fields of rapidly expanding supernovae remnants, according to the team.
"We have to keep our minds open about what dark matter could be," Kolb told New Scientist. "I think it's a brilliant idea that could have been prematurely rejected," he added.
According to Avi Loeb of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, "The nature of dark matter is not known, so it's always healthy and important to explore unconventional possibilities."
If dark matter is electrically charged, it would be more likely to collide with normal matter. That's because it could couple with ordinary matter through its magnetic fields.
The researchers are currently studying what properties CHAMPs would need to explain dark matter observations.
If dark matter is charged, it could have had a drastic effect on the universe soon after the big bang.
When the universe was very dense, particles of light, or photons, smoothed out subtle ripples in ordinary matter.
But dark matter is supposed to have remained clumpy after the big bang, creating small pockets of mass that drew in surrounding material to form larger structures such as galaxies.