A neutrino with 300 trillion electron volts traveled 4 billion light-years to reach Earth.
Key Takeaways:
- For the first time, scientists have traced a high-energy neutrino back to its galactic birthplace, a blazar.
- The neutrino came from TXS 0506+056, a flaring blazar 4 billion light-years away in Orion.
- This discovery confirms that blazars emit both neutrinos and cosmic rays, solving a long-standing mystery.
- The IceCube observatory in Antarctica detected the neutrino on September 22, 2017, leading to worldwide telescope observations.
- Neutrinos travel unaffected by magnetic fields, making them powerful cosmic messengers revealing the universe’s high-energy secrets.
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A Breakthrough in Neutrino Astronomy
For the first time, scientists have identified the origin of a high-energy neutrino, a nearly massless particle that traveled 4 billion light-years before slamming into the Antarctic ice. This intergalactic particle was detected on September 22, 2017, by the IceCube Neutrino Observatory, which is embedded within a cubic kilometer of ice at the South Pole. The discovery marks a milestone in neutrino astronomy, an emerging field that uses these elusive particles to study extreme cosmic events.
Neutrinos are produced alongside cosmic rays—high-energy protons and atomic nuclei—by powerful cosmic accelerators. Until now, scientists had struggled to pinpoint their exact sources. But by tracing the neutrino’s trajectory, astronomers zeroed in on a flaring blazar called TXS 0506+056 in the constellation Orion. A blazar is a type of galaxy with a supermassive black hole at its center that shoots jets of high-energy particles toward Earth. This blazar’s gamma-ray flare, observed by NASA’s Fermi Gamma-ray Space Telescope and other observatories, provided strong evidence that it was the neutrino’s birthplace.
Unveiling Cosmic Accelerators
This discovery also has significant implications for understanding cosmic rays. While cosmic rays frequently bombard Earth, their paths are twisted by magnetic fields, making it difficult to trace them back to their sources. Neutrinos, however, are electrically neutral and travel in straight lines, providing a clear path to their origins. By confirming that blazars produce both neutrinos and cosmic rays, scientists now have a powerful new tool for studying the universe’s most extreme particle accelerators.
The breakthrough follows years of searching for high-energy neutrino sources. In a follow-up study published on July 13 in Science, IceCube researchers analyzed past data and found that TXS 0506+056 had emitted a flare of high-energy neutrinos between September 2014 and March 2015. This reinforces the link between blazars and these energetic particles.
Astrophysicists like Angela Olinto of the University of Chicago hail this as a pivotal moment in astrophysics. “What neutrinos gave us is a way through the fog,” she said, emphasizing how they can reveal hidden cosmic processes. While many questions remain—such as whether blazars can accelerate protons to the highest observed cosmic ray energies—this discovery brings scientists closer to understanding the universe’s most powerful forces.
