IceCube Neutrino Observatory Reveals Map of Cosmic Neutrinos’ Origin
In a groundbreaking discovery, the IceCube Neutrino Observatory has finally collected enough cosmic neutrinos to unveil their origin. Neutrinos, the elusive particles that pass through us every second, have puzzled astrophysicists for decades as they travel from powerful sources in the universe.
Of the 100 trillion neutrinos that pass through us every second, the majority originate from the sun or Earth’s atmosphere. However, a few of these particles, moving much faster than the rest, come from distant sources. The IceCube Neutrino Observatory has recently detected enough cosmic neutrinos to identify telltale patterns in their origin.
In a recent paper published in Science, the IceCube team revealed the first map of the Milky Way in neutrinos. The map shows a diffuse haze of cosmic neutrinos emanating throughout the galaxy, but surprisingly, no specific sources stand out. “It’s a mystery,” said Francis Halzen, leader of the IceCube project.
This discovery follows a previous study by IceCube, also published in Science, which connected cosmic neutrinos to an individual source. The study revealed that a significant portion of the detected cosmic neutrinos originated from the heart of an “active” galaxy called NGC 1068. In the core of this galaxy, matter spirals into a supermassive black hole, generating cosmic neutrinos.
The identification of cosmic neutrino sources opens up the possibility of using these particles as a new probe of fundamental physics. Neutrinos have the potential to challenge the reigning standard model of particle physics and test quantum descriptions of gravity.
However, this is just the beginning of understanding cosmic neutrinos’ origins. Little is known about how activity around supermassive black holes generates these particles, and the evidence suggests multiple processes or circumstances.
Detecting cosmic neutrinos is no easy task. IceCube, which was built 12 years ago, consists of kilometer-long strings of detectors buried deep in the Antarctic ice. Each year, IceCube detects a dozen or so cosmic neutrinos that stand out among the background of atmospheric and solar neutrinos. More advanced analysis can identify additional candidate cosmic neutrinos from the data.
According to astrophysicists, energetic neutrinos can only be produced when fast-moving atomic nuclei, known as cosmic rays, collide with material in space. Only a few places in the universe have magnetic fields strong enough to accelerate cosmic rays to these energies. Gamma-ray bursts and active galactic nuclei (AGNs) were considered the most likely sources. AGNs are galaxies with central supermassive black holes that emit particles and radiation as matter falls into them.
The discovery of the origin of cosmic neutrinos is a significant step forward for neutrino astronomy. It not only provides insights into the universe’s workings but also offers opportunities to explore fundamental physics further. As scientists continue to unravel the mysteries surrounding cosmic neutrinos, the field of astrophysics is poised for exciting advancements.
Illustration: Merrill Sherman/Quanta Magazine; images courtesy of IceCube Collaboration