The neutrino had originated from a distant galaxy.
The total number of neutrinos (a particle with zero charge and practically zero mass) is probably equal to the total number of grains of sand on all the seashores of the world.
The detection of a neutrino last September by iceCube, an observatory near the South pole, caused quite a stir in the scientific world. However, before I discuss this spectacular development, I would like to give a short account of the neutrino’s scientific history.
What do events in the universe such as a) gamma ray bursts from exploding stars b) violent turmoil at the cores of distant galaxies c) colliding black holes d) nuclear reactions inside planets and stars e) supernovas f) accelerated particle beams or cosmic rays striking the earth and g) various radioactive decays, including beta decay of atomic nuclei or hadrons- all have in common?
They are all astrophysical phenomena. But they have in common something of far greater significance. In all these interactions, and events a neutrino is created.
According to scientists there are a million neutrinos per cubic centimetre of space which works out to billion neutrinos for every particle of ordinary matter. It is inconceivable that at any given time there are about one hundred billion neutrinos inside one’s body without making their presence felt.
Almost all are surviving objects dating back to the first three seconds after the big bang. The weak interaction of neutrinos with ordinary matter makes it absolutely unlikely that even one of them will be stopped in your body in your lifetime.
It is this very property that enabled iceCube to detect the neutrino. Its instruments consist of a telescope and thousands of sensors buried 1450 to 1650 metres below the surface of the ice and spread over a cubic km of volume. The sensors of iceCube send digital data to the counting house on the surface above the ice.
The existence of the neutrino had been postulated in 1930 by the Austrian physicist Pauli and later claimed to have been detected by Cowan and Reines in 1956, who 40 years later got their Nobel Prize.
However, it was iceCube that enabled scientists to systematically study its movement from the place it originated till it entered the ice beneath the Arctic surface, making its presence felt when it bathed the instruments beneath the ice in a flash of light, last year.
Astronomers concluded that the particle, was indeed a neutrino and that it had originated from a distant galaxy. Apart from that the telescope of iceCube found that the particle was generated in the womb of a blazar, a hitherto unknown astrophysical entity.
A supermassive black hole gives rise to a blazar as a source of radiation. Thus the significance of the discovery of the arrival of the neutron in the region below iceCube was three- fold- 1) that a neutrino, a particle of zero charge and almost zero mass does exist, in unimaginable numbers throughout the universe 2) that the neutrinos come from far off regions outside our galaxy- barring just a few, which originate from the sun, and 3) that the source of the neutrino that was detected by IceCube is a blazar, whose existence scientists came to know for the first time. Scientists however strike a note of caution that plenty of research has to be done before it can be concluded that blazars are sources of neutrinos.