Mining neutrinos



Ore from a mine nearly a mile deep may hold a record of stellar collapses in our galaxy over millions of years, say two physicists in a new study. The results of their work could place constraints on the rate of supernova formation and the evolution of matter.

Neutrinos are a key to many stellar processes, from the life of the Sun to the death of the Sanduleak star in the large Magellanic Cloud, reincarnated last year as Supernova SN 1987A. Most scientists now agree that when a supernova forms, 99% of the energy that held the atoms in the star together is released as neutrinos, virtually massless particles that interact very weakly with matter. In the few seconds after SN 1987A was born, ∼1058 neutrinos passed through Earth. Neutrinos are also continually produced in the Sun by nuclear reactions like electron capture and beta decay; by one estimate, ∼3×1029 solar neutrinos go through Earth each second. In addition, the collapse of stars elsewhere in the galaxy releases neutrinos that eventually reach Earth.