Neutrino Traced to Distant Blazar

The high-energy neutrino that reached Earth on September 22, 2017,

was not unusual by itself. Scientists at the IceCube Neutrino Observatory in Antarctica

detect neutrinos with similar energy about once a month. What made this one remarkable was that

it carried enough information about its path for astronomers to trace it back to its source.

Using that data, they aimed telescopes in the right direction and discovered that the neutrino had

been launched toward Earth about 4 billion years ago by a flaring blazar—a supermassive black hole at the

center of a distant galaxy that was actively consuming surrounding material.