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Utah physicists want to know what is firing off the strongest particles in the universe.
To investigate the energy-dense cosmic rays, they will need to update their toolkit, including the $25 million Telescope Array observatory about 130 miles south of Salt Lake City.
The expansion will require an additional $6.4 million, the University of Utah announced Monday.
Japan has stepped up to help, sending over $4.6 million to quadruple the 300-square-mile observatory near Delta. A National Science Foundation grant this fall is expected to cover the $1.8 million difference.
Physicists believe a so-called "hot spot" galaxies away is sending out subatomic flecks packed with energy.
"We have a really good, strong hint," said U. astronomy professor Pierre Sokolsky. "We know where the cosmic rays are concentrated in the sky. A group of galaxies is hiding behind there, producing those extraordinary particles."
The observatory is the only one of its kind in the Northern Hemisphere. The planned expansion would make the telescope array nearly as big and as sensitive as its rival, the Pierre Auger cosmic ray observatory in Argentina. Together, the two arrays monitor the northern and southern skies.
Utah's array will add 400 detectors spread out over a grid in the west desert. The array currently has 507 detectors. When the project is complete, the observatory will grow to almost 1,000 square miles. The plan is awaiting approval from administrators at the federal Bureau of Land Management and the agency overseeing Utah school trust lands.