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

12.11.2025

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.