Princeton physicists study sunshine

PRINCETON, N.J., Aug. 22 (UPI) -- U.S. physicists confirmed a long-held theory about the source of sunshine by exploring subatomic particles beneath Italian mountains.

The Princeton University researchers, working as part of an international collaboration at the underground Gran Sasso National Laboratory near L'Aquila, Italy, accomplished the first real-time observation of low-energy solar neutrinos, which are fundamental particles created by nuclear reactions that stream in vast numbers from the sun's core.

"Our observations essentially confirm that we understand how the sun shines," said Professor Frank Calaprice, principal investigator of the Princeton team. "Physicists have had theories regarding the nuclear reactions within the sun for years, but direct observations have remained elusive. Now we understand these reactions much better."

The scientists said their precise measuring of the neutrinos' energy using the Borexino detector -- located about 1/2 mile below the Earth's surface -- provides long-sought proof of the theory regarding how such neutrinos are produced.

The findings of the experiment, which involved more than 100 scientists worldwide, are to appear in an upcoming issue of the journal Physics Letters B.