Integral data have been used to reach this conclusion

Aug 3, 2009 06:48 GMT  ·  By
For the first time, positron annihilation is found to be asymmetric in the inner Galactic disk. Consistent with earlier findings, the annihilation emission is brightest around the Galactic center
   For the first time, positron annihilation is found to be asymmetric in the inner Galactic disk. Consistent with earlier findings, the annihilation emission is brightest around the Galactic center

According to scientists who went through the massive volumes of data beamed back by the European Space Agency's (ESA) Integral observatory, the peculiar radiations that permeate our galaxy, the Milky Way, are not caused by the elusive dark matter, as previously believed. These types of radiations were identified for the first time in the 1970s, and researchers have since proposed a number of theories trying to explain them, including dark matter. However, the advanced observation abilities of the satellite have shown that this is not the case, and that the radiation exhibits a spike towards the center of the galaxy, with an asymmetry along the galactic disk, ScienceDaily informs.

The observatory has unprecedented spatial and spectral resolution for an instrument of its kind, and the amount of data it collected – that led to the new study – cannot be misinterpreted. Some astronomers believed that dark matter was responsible for the weird readings because of its traits, which include exerting a strong gravitational pull on all galaxies in the Universe. Other telescope data seem to point at the fact that the elusive matter, which has thus far avoided detection, also forms a halo of sorts around the most massive galaxies, such as our own.

The most intriguing elements that are found in galactic core radiations are positrons, the antimatter counterparts of electrons. When the two types of particles meet, they annihilate each other and disappear. Thus far, it was believed that dark matter was the main source of positrons, but the new study seems to suggest that they actually come from massive stars, which exploded into supernovas. When the explosion occurs, large amounts of radioactive materials are emitted, which decay over time into lighter particles, including positrons.

The main argument behind the dark matter hypothesis was considered to be flawless. With positrons being the counterparts of electrons, it would stand to reason that they have positive charges. This means that they are influenced by magnetic fields, and that, therefore, they cannot travel large distances. In the new research, conducted by University of California in San Diego (UCSD) experts, and led by astronomer Richard Lingenfelter, it was shown that these positrons produced from the natural decay of radioactive elements from massive stars could actually travel extended distances, even beyond the galactic disk.

Details of the paper appear in the latest issue of the scientific journal Physical Review Letters.