BBC:
The origin of the highest-energy cosmic rays—charged
subatomic particles that streak to Earth from outer
space—may be one of the longest-standing questions in
astrophysics. Only two sources were thought possible,
supermassive black holes or gamma-ray bursts (GRBs). Now
researchers at the IceCube neutrino telescope, who published
their
findings yesterday in
Nature, say that GRBs are not the sole source of the
high-energy cosmic rays. Computer models had predicted that
GRBs would generate a stream of neutrinos, among other
particles. However, over a period of two years when some 300
GRBs were recorded by NASA's
Swift spacecraft and other observatories, IceCube
scientists did not detect the levels of neutrinos that GRBs
should produce. IceCube is searching for neutrinos from active
galactic nuclei, but the results so far have been
inconclusive.
