University of Maryland, College Park | 2017 Nov 16
UMD-led HAWC collaboration suggests dark matter as possible culprit
A mountaintop observatory in Mexico, built and operated by an international team of scientists, has captured the first wide-angle view of gamma rays emanating from two rapidly spinning stars. The High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory provided the fresh perspective on high-energy light streaming from these stellar neighbors, casting serious doubt on one possible explanation for a mysterious excess of anti-matter particles near Earth.
In 2008, astronomers observed an unexpectedly high number of positrons—the anti-matter cousins of electrons—in orbit a few hundred miles above Earth’s atmosphere. Ever since, scientists have debated the cause of the anomaly, split over two competing theories of its origin. Some suggested a simple explanation: The extra particles might come from nearby collapsed stars called pulsars, which spin around several times a second and throw off electrons, positrons and other matter with violent force. Others speculated that the extra positrons might come from processes involving dark matter—the invisible but pervasive substance seen so far only through its gravitational pull.
Using new data from the HAWC observatory, researchers made the first detailed measurements of two pulsars previously identified as possible sources of the positron excess. By catching and counting particles of light streaming from these nearby stellar engines, HAWC collaboration researchers found that the two pulsars are unlikely to be the origin of the positron excess. Despite being the right age and the right distance from Earth, the pulsars are surrounded by an extended murky cloud that prevents most positrons from escaping ...
Extended Gamma-Ray Sources Around Pulsars Constrain the Origin of the Positron Flux at Earth - A. U. Abeysekara et al
- Science 358(6365):911 (17 Nov 2017) DOI: 10.1126/science.aan4880