Sky-high observatory sheds light on origin of excess anti-matter

New study excludes nearby pulsars, points to dark matter as possible culprit
Chris Cesare, Miguel Mostafá, Gail McCormick
November 16, 2017

UNIVERSITY PARK, Pa. — The High-Altitude Water Cherenkov (HAWC) Observatory in Mexico, built and operated by an international team that includes Penn State scientists, has captured the first wide-angle view of very-high-energy light emanating from two rapidly spinning stars. The fresh perspective on these stellar neighbors — which are both close to Earth in cosmic terms — casts serious doubt on one possible origin for a mysterious excess of particles near Earth whose origin has tantalized scientists in recent years.

“Scientists have debated the cause of an unexpectedly high number of positrons — the anti-matter cousins of electrons — near the Earth since a space-borne detector measured the anomaly in 2008,” said Miguel Mostafá, professor of physics and of astronomy and astrophysics and principal investigator of the HAWC group at Penn State. “Some have speculated that the extra positrons have an exotic source, perhaps originating from as-yet undetected processes involving dark matter — the invisible but pervasive substance seen only through its gravitational pull. Others have suggested something more pedestrian: The extra particles might originate from nearby collapsed stars, called pulsars, that spin around several times a second and throw off electrons, positrons and other matter with violent force.”

Now, using new data from the HAWC Gamma-Ray Observatory, an international team of researchers has made the first detailed measurements of two pulsars, Geminga and its unnamed sibling, that had been identified as possible sources of the mysterious excess of positrons. By catching and counting particles of light streaming forth from these nearby stars, the HAWC collaboration has shown that the two pulsars are very unlikely to be the origin of the positron excess despite being the right age and the right distance from Earth to contribute. Positrons from these sources simply have not traveled far enough to reach the Earth in great numbers. The results appear in the Nov. 17 issue of the journal Science.

“After excluding two of the main source candidates, we are closer to understanding the origin of the positron excess,” said Francisco Salesa Greus, lead author of the new paper. A postdoctoral researcher in the HAWC group at Penn State at the time of the research, Salesa Greus is now at the Polish Academy of Sciences Institute of Nuclear Physics in Krakow, Poland.

More:
http://news.psu.edu/story/493719/2017/11/16/research/sky-high-observatory-sheds-light-origin-excess-anti-matter

Science:
https://www.democraticunderground.com/122854390



High-Altitude Water Cherenkov (HAWC) Observatory in Mexico







More images:

https://images.search.yahoo.com/search/images;_ylt=AwrTcXYJ6Q1aeQ8AdmCLuLkF;_ylc=X1MDOTYwNTc0ODMEX3IDMgRiY2sDZWFlcjdmOWNnbDI5ZyUyNmIlM0Q0JTI2ZCUzRGZFVE9PSzFyWUgzS3VfNWJGaWk4THF3a19jX3JYc19ya1E2azM1dGQ0N2NwM1EtLSUyNnMlM0RkayUyNmklM0RFMjZMeTNLQ2t5MmdRdWtvSzI5bARmcgMEZ3ByaWQDUzNuOFZObFhSYS4ub284RDMxU2tOQQRtdGVzdGlkA251bGwEbl9zdWdnAzAEb3JpZ2luA2ltYWdlcy5zZWFyY2gueWFob28uY29tBHBvcwMwBHBxc3RyAwRwcXN0cmwDBHFzdHJsAzU4BHF1ZXJ5A0hpZ2gtQWx0aXR1ZGUgV2F0ZXIgQ2hlcmVua292IChIQVdDKSBPYnNlcnZhdG9yeSBpbiBNZXhpY28EdF9zdG1wAzE1MTA4NjEwNjcEdnRlc3RpZANCNDI2MQ--?gprid=S3n8VNlXRa..oo8D31SkNA&pvid=CWDs_TEwLjLlO2d6WQqJMAKZMjYwMgAAAADBGLTg&fr2=sb-top-images.search.yahoo.com&p=High-Altitude+Water+Cherenkov+%28HAWC%29+Observatory+in+Mexico&ei=UTF-8&iscqry=&fr=sfp#id=185&iurl=http%3A%2F%2Fudg.mx%2Fsites%2Fdefault%2Ffiles%2Fimg_noticias%2F150317_laboratorio_rayos_gamma_ag_1.jpg&action=close