I’ve written elsewhere about neutrinos (aka “ghost particles”). The latest news is about a particular discovery — a major team effort — as to the source of some of the most energetic ones. Many articles. Some contain illustrations.
Most of these neutrinos come from the sun. But a small percentage, which boast extremely high energies, have rocketed to our neck of the woods from very deep space. The inherent elusiveness of neutrinos has prevented astronomers from pinning down the origin of such cosmic wanderers — until now.
Scientists have spotted a high-energy, incredibly tiny “ghost” particle called a neutrino flying through Antarctic ice and traced its origins back to a specific blazar, they announced today, July 12.
The IceCube Laboratory at the Amundsen-Scott South Pole Station in Antarctica is the world’s largest neutrino detector. Its computers collect raw data on neutrino activity from sensors in the ice that look for light emitted when neutrinos strike.
This illustration shows how muon neutrinos can arrive at the IceCube detector via different paths through the Earth. Neutrinos with higher energies and with incoming directions closer to the North Pole are more likely to interact with matter on their way through Earth.
A blazar accelerates protons (the yellow p) to the energy levels of cosmic rays, initiating a complex quantum cascade that also releases gamma rays (magenta) and neutrinos (blue), which follow straight paths through space. The coupled detection of these two particles [“multimessenger” emission] enabled astronomers to identify the blazar as a source of cosmic rays.
Multimessenger astronomy involves synthesizing information from multiple sources. Astronomers can currently gather data from these four messengers. Here, gamma rays stand in for the entire electromagnetic spectrum, which spans radio waves, through optical light, to gamma rays.
Fermi is designed to examine gamma-ray radiation, the most energetic form of light that there is. Like the visible light that humans can see, gamma-rays are on the spectrum of electromagnetic radiation. Gamma-rays, however, have billions of times more energy than visible light.
In NASA’s words, these are the main mission objectives for Fermi:
Explore the most extreme environments in the universe, where nature harnesses energies far beyond anything possible on Earth.
Search for signs of new laws of physics and what composes the mysterious dark matter.
Explain how black holes accelerate immense jets of material to nearly light speed.
Help crack the mysteries of the stupendously powerful explosions known as gamma-ray bursts.
Answer long-standing questions across a broad range of topics, including solar flares, pulsars and the origin of cosmic rays.
One thought on “Blazar neutrinos”
Detection of a most awesome neutrino sparks research.
Spotted on October 1, 2019, the little neutrino packed a punch: an energy of 200 trillion electron volts. That’s about 30 times the energy of the protons in the most powerful human-made particle accelerator, the Large Hadron Collider. The neutrino’s signature was picked up by IceCube, a detector frozen deep in the Antarctic ice. That detector senses light produced when neutrinos interact with the ice.
To have birthed such an energetic neutrino, the star-shredding event must have first accelerated protons to high energies. Those protons must then have crashed into other protons or photons (particles of light). That process produces other particles, called pions, that emit neutrinos as they decay.
Detection of a most awesome neutrino sparks research.
Science News > “A star shredded by a black hole may have spit out an extremely energetic neutrino” by Emily Conover (May 26, 2020) – If true, this would be only the second time such a neutrino has been traced back to its source.