The IceCube telescope in the South Pole found no neutrinos (Image: NSF/S. Lidstrom)

The failure of ghostly subatomic messengers called neutrinos to show up at an Antarctic telescope has knocked down a major astrophysical theory involving some of the most dramatic explosions in the universe.

“I would have preferred to have seen neutrinos,” says the IceCube telescope’s principal investigator Francis Halzen at the University of Wisconsin, Madison. “Null results are usually not very interesting, but in this case, it is.”

Neutrinos are emitted by a range of cosmic processes. Most stream through matter without being deflected or changed, making them ideal long-distance messengers from distant galaxies.


The IceCube telescope monitors a cubic kilometre of ice beneath the South Pole for neutrinos of various types, including the cosmic variety. Vertical strings of detectors frozen into the ice watch for flashes of blue light emitted when neutrinos strike. The energy of the neutrino determines its source.

Collapsing star

One source of neutrinos was thought to be explosions known as gamma ray bursts (GRBs) – via mysterious entities called ultra high energy cosmic rays.

UHECRS, very high energy protons and charged nuclei, occasionally arrive on Earth , where they are detected by cosmic ray detectors such as the Pierre Auger Observatory in Argentina. UHECRs are known to come from outside our galaxy, but because they get deflected by magnetic fields en route, it’s impossible to retrace their path and determine their source.

GRBs, thought to occur when massive stars collapse to form black holes, could spew out such particles. If they do, the UHECRs should interact with the photons also streaming out of the explosion to form neutrinos with energies in the hundreds of tera-electronvolts. These should then arrive on Earth along with the photons.

With this chain of events in mind, IceCube has been looking for neutrinos occurring at the same time as GRBs. From May 2009 to May 2010, gamma-ray satellite observatories saw 190 GRBs. Theory predicts that IceCube should have seen a handful of neutrinos at the same time, from the same region of the sky. But today IceCube reports that it saw absolutely nothing – a serious blow to a cascade of processes astrophysicists thought they understood.

Supermassive black holes

Most importantly, the result removes a leading explanation for UHECRs. “That GRBs are the source of the cosmic rays is basically ruled out,” says Halzen. “We have put half the theorists out of business.”

Theorist Dan Hooper of Fermilab in Batavia, Illinois, agrees: “Given that GRBs were a leading candidate for the origin of these, this is an important result,” he says.

Attention will now shift to active galactic nuclei (AGN), which are powered by supermassive black holes. AGNs could also produce UHECRs and because the mechanism for their production would be different, this is not ruled out by today’s IceCube result. “We could observe neutrinos from AGNs any day and prove that they are the source of the cosmic rays,” says Halzen.

Journal reference: Nature, DOI:10.1038/nature11068