银河中的伽马射线可作为暗物质存在的证据

Gamma-ray photons（光子） seen emanating¹（放射） from the center of the Milky² Way galaxy³ are consistent with the intriguing⁴（有趣的） possibility that dark-matter particles are annihilating⁵（消灭） each other in space, according to research submitted by UC Irvine astrophysicists to the American Physical Society journal Physical Review D. Kevork Abazajian, assistant professor, and Manoj Kaplinghat, associate professor, of the Department of Physics & Astronomy analyzed⁶ data collected between August 2008 and June 2012 from NASA's Fermi Gamma-ray Space Telescope orbiting Earth. They found more gamma-ray photons coming from the Milky Way galactic center than they had expected, based on previous scientific models. Gamma-rays are electromagnetic radiation emitted during radioactive decay or other high-energy particle processes.   "This is the first time this new source has been observed with such high statistical⁷ significance, and the most striking part is how the shape, spectrum⁸ and rate of the observed gamma rays are very consistent with the leading theories for dark matter," Abazajian said. "Future observations of regions with less astrophysical（天体物理学的） emission⁹, such as dwarf¹⁰ galaxies¹¹, will be able to conclusively¹² determine if this is actually from the dark matter."   Nonluminous and not directly detectable¹³, dark matter is thought to account for 85 percent of the universe's mass. Its existence can only be inferred from its gravitational effects on other, visible matter. The UCI researchers' findings could support its presumed presence at the center of galaxies.   The prevailing¹⁴ hypothesis is that dark matter is composed of weakly interacting massive particles, or WIMPs¹⁶. When two WIMPs meet, they annihilate¹⁷ each other to produce more familiar particles -- including gamma rays.   Although the data interpretation¹⁸ seems to be consistent with dark-matter theory, the gamma rays could be coming from a source other than WIMP¹⁵ destruction, Kaplinghat noted¹⁹. "The signal we see is also consistent with photons emitted by pulsars," he said, "or from high-energy particles interacting（相互作用） with gas in the galactic center."