Tag Archives: IceCube

Astronomers track neutrino from galaxy 3.7 billion light years away

Using multiple telescopes astronomers have successfully tracked the source of a neutrino that was detected on September 22 2017 by the IceCube neutrino telescope in Antarctica to a galaxy 3.7 billion light years away.

Because scientists on the IceCube experiment had worked out the path the particle took through their subterranean ice instrument, astronomers knew where in the sky to look for the particle’s source. A string of early observations came up blank, but days later Nasa’s Fermi Gamma-ray Space Telescope spotted the likely source: a flaring “blazar”.

Most galaxies are thought to have spinning supermassive black holes at their centres. But some of these black holes appear to pull in material at ferocious rates, a process that simultaneously sends streams of highly energetic particles out into space. Such galaxies are called blazars, although the term only applies when one of these streams is directed straight at Earth.

The blazar that appears to have sent the neutrino our way lies 3.7bn light years from Earth, just off the left shoulder of the constellation of Orion. While a single detection is not strong evidence, the IceCube scientists went back through their records and found a flurry of neutrinos coming from the same spot over 150 days in 2014 and 2015.

This I think is the first time scientists have linked a neutrino to its source, outside our solar system. Most neutrino detections come from the Sun. That they could trace this one back to a blazar so far away means their neutrino telescopes are now becoming sensitive enough to find and study the neutrinos coming from other sources.

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Physicists fail to find sterile neutrino

The uncertainty of science: A year’s collection of data using IceCube, a gigantic neutrino telescope built in the icecap of Antarctica, has found no evidence of a theorized fourth type of neutrino.

To search for sterile neutrinos, Halzen’s team looked for the arrival of muon neutrinos that started life on the other side of Earth. These were originally produced by the collision of cosmic rays with air molecules in the atmosphere, and passed through the planet to reach the detector. The IceCube team hoped to find a dearth of muon neutrinos at particular energies. That would have suggested that some muon neutrinos had temporarily mutated into sterile neutrinos during their voyage.

But, after analysing the results of a year’s worth of data, the researchers found no feature suggesting the existence of sterile neutrinos around 1 eV. This is line with results from the European Space Agency’s Planck observatory, which concluded from cosmological evidence that there should only be three families of neutrinos in that mass range. “I hope that with our result and with the Planck result we are slowly walking our way back from this story,” says Halzen. The IceCube team are still taking data in their sterile neutrino hunt, but don’t expect their results to change, he adds.

Despite this null result, there is still a possibility that sterile neutrinos exist, but not at the mass predicted.

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New data from a neutrino telescope in Antarctica had found that cosmic rays don’t come from gamma ray bursts, as had been believed by astronomers.

The uncertainty of science: New data from a neutrino telescope in Antarctica has found that cosmic rays don’t come from gamma ray bursts, as had been believed by astronomers. You can read the paper here. [pdf]

Which means that astronomers at this moment have no idea what produces these high energy cosmic rays.

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