Neutrinos love complicated puzzles

by drd. Alice Mihaela Păun

23.05.2025

Neutrinos, also known as astrophysical messengers due to the vast distances they can travel through the Universe without interacting with matter, are extremely difficult to detect. For the detection of these particles, it was necessary to construct a neutrino telescope with a volume of 1 km³ and place it deep within the ice at the South Pole - the IceCube Neutrino Observatory [https://icecube.wisc.edu/]. Neutrinos that interact near the detector produce relativistic particles that generate luminous events, which can be "seen" by the "eyes" of the instrumentation (optical modules).

The data collected by IceCube concerning the galaxy NGC 1086 [1], also known as the Squid Galaxy, indicate a flux of very high-energy neutrinos (TeV), accompanied by an extremely weak flux of gamma rays (GeV) observed by the Fermi [2] and MAGIC [3] telescopes. NGC 1086 is an active galaxy with a central region (AGN – Active Galactic Nucleus) that contains a supermassive black hole and emits matter and energy in the form of jets. The discrepancy between the two particle fluxes represents an intriguing puzzle for researchers, because such active galactic nuclei typically emit neutrino and gamma-ray fluxes of comparable energies, resulting from interactions between protons and photons [4].

A recent article [5] offers a bold explanation for the neutrino puzzle observed from AGNs, which aligns with current observations: a new mechanism for producing high-energy neutrinos.
The source of the neutrino flux could be the corona — a region of dense, hot plasma surrounding the central supermassive black hole. The most abundant elements in the Universe are hydrogen and helium. Therefore, if a helium nucleus is accelerated in the jets of a supermassive black hole, it can collide with ultraviolet photons and "break apart", releasing its two protons and two neutrons [4]. Protons have a long lifetime, but neutrons are unstable and decay into high-energy neutrinos without producing gamma rays. The electrons generated in the decay interact with radiation fields and produce gamma rays that match the observed data.

The results of this study help us better understand how matter jets in active galaxies work and how high-energy neutrinos can be produced without a corresponding flux of gamma rays.

Galaxia Messier 77

Sursa foto: ESA/Hubble & NASA, L. C. Ho, D. Thilker

New Gravitational Waves Detector Configurations Were Discovered with the Help of Artificial Intelligence

by Maria Ișfan, PhD student

16.05.2025

Photo: https://humansofligo.blogspot.com/, https://news.mit.edu/

LIGO is a gravitational waves detector which operates according to the Michelson laser interferometry principle. The detector configuration is typical. It involves two perpendicular laser beams, along with optical elements such as mirrors and beam splitters.

Using only one laser beam, ten mirrors and beam splitters and two sensors, over one hundred million detector configurations can be obtained. With the help of the Urania artificial intelligence software, the researchers found fifty configurations which are better than the original one.

Compared to LIGO, these potential new detectors show increased sensitivity, have lower noise levels and are able to better observe the post-coalescence signal emitted by two neutron stars.

This new approach can be used for designing experiments in all areas of Physics, accelerating new scientific discoveries.

News source: https://journals.aps.org/prx/pdf/10.1103/PhysRevX.15.021012

Ancient footsteps in space-time

by Florentina Pîslan, PhD student

09.05.2025

Currently, we know gravitational waves can be divided into four distinct categories based on their sources, detection methods, and frequencies: stochastic, continuous, inspiral, and burst. When two black holes collide, they create inspiral gravitational waves that not only propagate through the Universe, but also leave a permanent imprint on the space-time continuum - much like how a chair leaves an indentation in a carpet. This phenomenon is called the 'memory effect,' which could hold the key to discovering small, ancient black holes potentially formed in the early Universe, known as Primordial Black Holes (PBHs).

Why are these objects so fascinating? Because they might be fragments from the Big Bang (even older than stars!) - as small as a city, yet as dense as a planet, and possibly the leading candidates for dark matter.

In the paper 'Gravitational Wave Memory of Primordial Black Hole Mergers’ , researchers investigate whether future gravitational wave observatories like LISA and the Einstein Telescope could detect these objects. The detectors will aim to identify them both through the characteristic 'chirp' signal produced during collision and by analyzing their space-time imprint. To better understand the difference: the 'chirp' resembles an explosive but transient sound, while the memory effect is more like a permanent scar. Generally, the more massive the objects producing the 'chirp,' the easier the signal is to detect.

The study reveals that due to the tiny size of Primordial Black Holes, the memory effect might be their only detectable signature. Observing this effect could provide groundbreaking confirmation of Einstein's predictions in entirely new ways.

Even more moons

by Florin Constantin, PhD student

03.11.2025

Credit imagine: NASA/JPL/Caltech

In March, the International Astronomical Union (IAU) has formally recognized the discovery of 128 new moons belonging to Saturn. After this discovery, the total number of moons the planet Saturn has reached 274, the most currently known of any planet in our solar system. A moon is any celestial body naturally formed that orbits another celestial body.

The discovery was made in 2023 by a group of scientists form multiple countries, who used images taken with the Canada-France-Hawaii Telescope. The “new” moons have small diameters of only a few kilometers and have irregular shapes. Many of them also seem to orbit in groups, which can suggest that they share the same origin. For the moment, they were given strings of numbers and letters for names until the official names will be decided. In order to keep with the tradition of using the names of gods, names from the Norse, Inuit and Gallic pantheons are being taken into consideration.

This discovery can provide information into the early period of our solar system, when a plethora of collisions between celestial bodies took place, but to the formation of Saturn’s rings as well.

The complete list of the currently known Saturn’s moons can be found here.

KM3NET DETECTS THE HIGHEST ENERGY NEUTRINO EVER OBSERVED

12.02.2025

‍From the abyss of the Mediterranean Sea, the KM3NeT Collaboration announces the detection of a cosmic neutrino with a record-breaking energy of about 220 PeV…

‍

‍An extraordinary event consistent with a neutrino with an estimated energy of about 220 PeV (220 million billion electron volts), was detected on February 13, 2023 by the ARCA detector of the kilometre cubic neutrino telescope (KM3NeT) in the deep sea. This event, named KM3-230213A, is the most energetic neutrino ever observed and provides the first evidence that neutrinos of such high energies are produced in the Universe. After long and meticulous work to analyse and interpret the experimental data, today,

‍February 12, 2025, the international scientific collaboration of KM3NeT* reports the details of this amazing discovery in an article published in Nature.

‍The detected event was identified as a single muon which crossed the entire detector, inducing signals in more than one third of the active sensors. The inclination of its trajectory combined with its enormous energy provides compelling evidence that the muon originated from a cosmic neutrino interacting in the vicinity of the detector.

‍

‍“KM3NeT has begun to probe a range of energy and sensitivity where detected neutrinos

‍may originate from extreme astrophysical phenomena. This first ever detection of a

‍neutrino of hundreds of PeV opens a new chapter in neutrino astronomy and a new

‍observational window on the Universe.”, comments Paschal Coyle, KM3NeT

‍Spokesperson at the time of the detection, and researcher at IN2P3/CNRS Centre

‍National de la Recherche Scientifique – Centre de Physique des Particules de Marseille,

‍France.

‍

‍The high-energy universe is the realm of cataclysmic events such as accreting supermassive black holes at the centre of some galaxies, supernova explosions, gamma ray bursts, all as yet not fully understood. These powerful cosmic accelerators, generate streams of particles called cosmic rays. Some cosmic rays may interact with matter or photons around the source, to produce neutrinos and photons. During the travel of the most energetic cosmic rays across the Universe, some may also interact with photons of the cosmic microwave background radiation, to produce extremely energetic so-called “cosmogenic” neutrinos.

‍

‍“Neutrinos are one of the most mysterious of elementary particles. They have no electric

‍charge, almost no mass and interact only weakly with matter. They are special cosmic

‍messengers, bringing us unique information on the mechanisms involved in the most

‍energetic phenomena and allowing us to explore the farthest reaches of the Universe.”,

‍explains Rosa Coniglione, KM3NeT Deputy-Spokesperson at the time of the detection,

‍researcher at the INFN National Institute for Nuclear Physics, Italy.

‍

‍Although neutrinos are the second most abundant particle in the Universe after photons (light), their extremely weak interaction with matter makes them very hard to detect and requires enormous detectors. The KM3NeT neutrino telescope, currently under construction, is a giant deep sea infrastructure distributed across two detectors ARCA and ORCA. In its final configuration KM3NeT will occupy a volume of more than one cubic kilometre. KM3NeT uses sea water as the interaction medium for neutrinos. Its high-tech optical modules, detect the Cherenkov light, a bluish glow that is generated during the propagation through the water of the ultra-relativistic particles produced in neutrino interactions.

‍

‍“To determine the direction and energy of this neutrino required a precise calibration of

‍the telescope and sophisticated track reconstruction algorithms. Furthermore, this

‍remarkable detection was achieved with only one tenth of the final configuration of the

‍detector, demonstrating the great potential of our experiment for the study of neutrinos

‍and for neutrino astronomy”, comments Aart Heijboer, KM3NeT Physics and Software

‍Manager at the time of the detection, and researcher at Nikhef National Institute for

‍Subatomic Physics, The Netherlands.

‍

‍The KM3NeT/ARCA (Astroparticle Research with Cosmics in the Abyss) detector is mainly dedicated to the study of the highest energy neutrinos and their sources in the Universe. It is located at 3450 m depth, about 80 km from the coast of Portopalo di Capo Passero, Sicily. Its 700 m high detection units (DUs) are anchored to the seabed and positioned about 100 m apart. Every DU is equipped with 18 Digital Optical Modules (DOM) each containing 31 photomultipliers. In its final configuration, ARCA will comprise 230 DUs. The data collected are transmitted via a submarine cable to the shore station at the INFN Laboratori Nazionali del Sud.

‍The KM3NeT/ORCA (Oscillation Research with Cosmics in the Abyss) detector is optimised to study the fundamental properties of the neutrino itself. It is located at a depth of 2450 m, about 40 km from the coast of Toulon, France. It will comprise 115 DUs, each 200 m high and spaced by 20 m. The data collected by ORCA are sent to the shore station at La Seyne Sur Mer.

‍

‍"The scale of KM3NeT, eventually encompassing a volume of about one cubic kilometre

‍with a total of about 200 000 PMTs, along with its extreme location in the abyss of the

‍Mediterranean Sea, demonstrates the extraordinary efforts required to advance neutrino

‍astronomy and particle physics. The detection of this event is the result of a tremendous

‍collaborative effort between many international teams of engineers, technicians and

‍scientists.", comments Miles Lindsey Clark, KM3NeT Technical Project Manager at the

‍time of the detection, and research engineer at the IN2P3/CNRS - Astroparticle and

‍Cosmology laboratory, France.

‍

‍This ultra-high energy neutrino may originate directly from a powerful cosmic accelerator. Alternatively, it could be the first detection of a cosmogenic neutrino. However, based on this single neutrino it is difficult to conclude on its origin. Future observations will focus on detecting more such events to build a clearer picture. The ongoing expansion of KM3NeT with additional detection units and the acquisition of additional data will improve its sensitivity and enhance its ability to pinpoint cosmic neutrino sources, making it a leading contributor to multi-messenger astronomy.

‍

‍This article was taken from the official press release.

ASPACE-Q

The Astrophysics, Space Exploration and Quantum Computing Group