It hasn't replicated last year's results

May 7, 2009 18:41 GMT  ·  By
The LAT on Fermi has been unable to replicate ATIC's results on high-energy electrons in the upper Earth atmosphere
   The LAT on Fermi has been unable to replicate ATIC's results on high-energy electrons in the upper Earth atmosphere

During 2008, a number of scientific observations conducted in the upper atmosphere and in deep space yielded very promising results for research teams looking for the elusive dark matter around our planet. Large amounts of high-energy electrons were discovered just outside the Earth, and astronomers hypothesized that they might have come from an exotic form of dark matter, lurking all around us. But, unfortunately, these results have not been reproduced this year by the powerful Fermi Space Telescope, which has not seen the large amounts of high-energy electrons that were detected by previous experiments ATIC and PAMELA.

According to the prevailing theory, dark matter is entirely made up of weakly interacting massive particles (WIMP), which, when colliding in pairs of two, have the ability to counteract and annihilate each other. In the process, these collisions generate radiation, as well as a number of high-energy particles, including electrons. These super-charged particles are then sent through the Universe at high speeds, and can be detected by Earth- or orbit-based observatories.

Some astronomers believe that these high-energy particles around Earth may have come from more “domestic” sources, including pulsars and supernova remnants, which also have the ability to accelerate particles to energies of about 600 gigaelectronvolts. But experts concluded that the large number of electrons that could be found in these particles was a clear indicator of the fact that dark matter, maybe an exotic kind of it, was responsible for that. Another reason why they concluded this was because the PAMELA observatory, working in deep space, also recorded anomalous energy readings in a certain region of the galaxy, which mission controllers believed might have also originated in dark matter.

The team that coordinated the ATIC experiment said that their third balloon-borne mission to the upper atmosphere had revealed the same spikes in particle energies, and added that one of the reasons that could explain why Fermi was unable to register the variations would be because the orbital observatory had a thinner calorimeter than ATIC did. This instrument is directly responsible for detecting the energy of particles that hit it. Fermi's team admitted that their device was a bit less sophisticated than ATIC's, but argued that it was a lot better in other ways, namely in that it had a tool designed especially to be able to tell where particles were coming from, NewScientist reports.

“Particle physicists have not had much to get excited about in the last 10 years – they were all ready for the Large Hadron Collider and then had a big setback. Then PAMELA and ATIC came along with extra high-energy signals that could not be easily explained, and it was fun to think about,” Douglas Finkbeiner, who is an expert on the subject from the Harvard-Smithsonian Center for Astrophysics, said of the progress on finding dark matter.