Scientists using the IceCube Neutrino Observatory, buried in a cubic kilometre of Antarctic ice, have detected neutrinos carrying roughly 10 billion times the energy of typical solar neutrinos, ultra-rare 'ghost particles' that pass through matter almost undisturbed and may come from the universe's most extreme environments. The find comes as physicist Francis Halzen, whose vision led to the observatory, receives this year's Nobel Prize in Physics for the discovery of high-energy neutrinos of astrophysical origin.
Neutrinos are elementary particles with no electric charge and extraordinarily small mass, and they interact so weakly with matter that about 100 billion pass through every square centimetre of a person's body each second. Their near-invisibility has made them among the most difficult objects in the universe to detect.
'Neutrinos are truly ghost-like particles,' said George Fuller, a Distinguished Professor of Physics at the University of California San Diego who collaborated with Halzen on an early scientific paper. 'It's hard to stop them. It's hard to catch them. How do we even know they exist or where they are?'
Because neutrinos interact with matter through the weak force, which is roughly 20 orders of magnitude weaker than electromagnetism, they can travel through dense material almost without resistance. 'Because the interaction is so weak, neutrinos can get through almost anything,' Fuller said. 'Light years of lead, depending on their energy, they would go right through it.'
IceCube searches for brief flashes of blue light called Cherenkov radiation, produced when a neutrino interacts with the ice and creates a charged particle moving faster than light can travel through that material. The observatory detects only a few dozen of the most energetic neutrinos each year, and scientists analyse the pattern of light to estimate their energy and reconstruct their direction of arrival.
'Some ultra-high-energy neutrinos detected at IceCube have roughly 10 billion times the energy of a typical neutrino from the Sun,' Fuller said. 'One detected by a similar experiment has an energy 200 times higher than that. We don't really know where that neutrino came from. The fact that it got here at all may be saying something profound about the universe.'
The search for neutrinos began in the 1930s, when physicist Wolfgang Pauli proposed that an unknown particle might explain missing energy in radioactive decay, famously saying, 'I have done a terrible thing, I have postulated a particle that cannot be detected.' Neutrinos were first detected in 1956 in an experiment known as Project Poltergeist.
UC San Diego researchers are also involved in the Simons Observatory in Chile's Atacama Desert, which studies the cosmic microwave background, often described as the oldest light in the cosmos. Its measurements could reveal information about neutrinos from the earliest stages of cosmic history. 'Halzen's work, and the work of those he inspired with his vision, was foundational in giving humanity a new window on the universe and on the mysterious and notoriously slippery neutrino,' Fuller said.
Analysis
Why This Matters
- Neutrinos could reveal the processes at work in the universe's most extreme environments, such as collapsing stars and black holes, which other forms of radiation cannot escape.
- Understanding these particles may improve knowledge of the Big Bang and the early evolution of the universe.
- The Nobel recognition of Halzen highlights the scientific payoff of large-scale, decades-long physics infrastructure.
Background
Neutrinos are elementary particles with no electric charge and extremely small mass, first proposed by Wolfgang Pauli in the 1930s and detected in 1956. They come in three varieties and interact only through the weak force, making them very hard to observe. The IceCube Neutrino Observatory, built in clear ice beneath the South Pole, uses thousands of light detectors to catch the faint blue flashes produced when a rare neutrino interacts with matter.
What to Watch
- Whether further IceCube detections of ultra-high-energy neutrinos can be traced to specific cosmic sources, which remain unknown.
- The Simons Observatory's measurements of the cosmic microwave background, which could add new data on neutrinos from the early universe.
- Efforts to identify the origin of the most energetic neutrino yet seen, which Fuller says has 200 times the energy of the IceCube examples.
Checked
12 claims in this story checked against 1 source: 12 supported.
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- SupportedIceCube detected neutrinos with roughly 10 billion times the energy of typical solar neutrinos.Latest Science News -- ScienceDaily: “IceCube detects ghost particles with 10 billion times the energy of solar neutrinos.”
- SupportedFuller says Halzen’s work on the Antarctic observatory gave humanity a new window on the universe; Halzen received this year’s Nobel Prize in Physics.Latest Science News -- ScienceDaily: “This year, physicist Francis Halzen received the prestigious award "for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin."”
- SupportedIceCube is embedded in roughly one cubic kilometre of Antarctic ice.Latest Science News -- ScienceDaily: “His vision eventually led to the IceCube Neutrino Observatory, a gigantic scientific instrument embedded within roughly one cubic kilometer of Antarctic ice.”
- SupportedFuller said, “Neutrinos are truly ghost-like particles. It's hard to stop them. It's hard to catch them. How do we even know they exist or where they are?”Latest Science News -- ScienceDaily: “"Neutrinos are truly ghost-like particles," stated Fuller. "It's hard to stop them. It's hard to catch them. How do we even know they exist or where they are?"”
- SupportedAbout 100 billion neutrinos pass through each square centimetre of a person's body each second.Latest Science News -- ScienceDaily: “Approximately 100 billion neutrinos pass through every square centimeter of your body each second, almost entirely unnoticed.”
- SupportedThe weak interaction is roughly 20 orders of magnitude weaker than electromagnetism.Latest Science News -- ScienceDaily: “This force is approximately 20 orders of magnitude weaker than electromagnetism.”
- SupportedFuller said, “Because the interaction is so weak, neutrinos can get through almost anything. Light years of lead, depending on their energy, they would go right through it.”Latest Science News -- ScienceDaily: “"Because the interaction is so weak, neutrinos can get through almost anything," said Fuller. "Light years of lead -- depending on their energy, they would go right through it."”
- SupportedFuller said that some ultra-high-energy IceCube neutrinos have roughly 10 billion times the energy of a typical solar neutrino, and that one detected by a similar experiment had 200 times higher energy; he said its origin was unknown.Latest Science News -- ScienceDaily: “"Some ultra-high-energy neutrinos detected at IceCube have roughly 10 billion times the energy of a typical neutrino from the Sun. One detected by a similar experiment has an energy 200 times higher than that. We don't really know where that neutrino came from," he stated.”
- SupportedPauli said, “I have done a terrible thing, I have postulated a particle that cannot be detected.”Latest Science News -- ScienceDaily: “He famously acknowledged the problem by saying, "I have done a terrible thing, I have postulated a particle that cannot be detected."”
- SupportedNeutrinos were first detected in 1956 in an experiment known as Project Poltergeist.Latest Science News -- ScienceDaily: “That changed in 1956, when physicists Clyde Cowan and Frederick Reines successfully detected them in an experiment known as "Project Poltergeist."”
- SupportedThe Simons Observatory in Chile’s Atacama Desert studies the cosmic microwave background, and its measurements could reveal information about neutrinos from the earliest stages of cosmic history.Latest Science News -- ScienceDaily: “Located high in Chile's Atacama Desert, the Simons Observatory is gathering information about the cosmic microwave background, the ancient radiation left over from the early universe.”
- SupportedFuller said Halzen’s work and that of those inspired by his vision was foundational in giving humanity a new window on the universe and the neutrino.Latest Science News -- ScienceDaily: “"Halzen's work, and the work of those he inspired with his vision, was foundational in giving humanity a new window on the universe and on the mysterious and notoriously slippery neutrino," he stated.”
