last September, a rare guest from far beyond the Milky Way ushered in a new era of astronomy. The visitor, an ultrahigh-energy cosmic neutrino, bumped into ice more than a mile beneath the South Pole, where detectors from the IceCube experiment were waiting to catch it. After quickly tracking the direction from where it came, physicists got lucky: Another telescope, this one orbiting Earth, spotted a stream of extremely energetic radiation coming from the same direction.

The twin events could have been a cosmic coincidence. But when physicists looked through their archived data, they found several other neutrinos that appear to have come from the same direction. This supporting evidence has convinced them that they’ve achieved a cosmic first: tracing ultrahigh-energy neutrinos back to their astrophysical source.

That source appears to be a supermassive black hole at the center of a distant galaxy. Every time a black hole gobbles up a star, it spews out a stream of very high-energy radiation in the form of a laserlike jet. Astronomers say that it “flares.” They call these flaring black holes blazars and believe that energetic neutrinos are created as a by-product of the radiation.

The find, described in a series of two papers published in Science, has not only settled a long-standing debate in astronomy over the origin of high-energy neutrinos. This discovery is also the second example (after last year’s observation of colliding neutron stars) of a new scientific approach called multimessenger astronomy, in which astronomers use both light and another cosmic messenger (neutrinos in this case, gravitational waves in the other) to reveal the details of an astrophysical event. “This is like getting an entirely new way of looking at the universe,” said Roopesh Ojha, an astrophysicist at NASA Goddard Space Flight Center.