Sign of a black hole falling into a star

by Andrei Militaru

03.10.2025

Photo source: https://scitechdaily.com/hawking-stars-what-happens-if-you-put-a-black-hole-into-the-sun/

The most luminous electromagnetic events we had observed in the universe are gamma-ray bursts. On july 2, 2025, The Fermi Gamma-ray Burst Monitor and many others X-ray and Gamma-ray monitors have identified the longest gamma-ray burst that has ever been seen. 

The common source for such events are collapsing stars, but the duration of this burst is much longer than what this explanation allows. After going through other possible scenario, including neutron star mergers, supermassive black holes merger, and a white dwarf tidal disruption by a black hole, Eliza Neights and Eric Burns conclude that the likely cause of this burst is the fall of a black hole inside a massive helium star.

When the back hole reaches the core of the star, the core is turned into an accretion disk, and the resulting magnetic field causes the star to explode and create a supernova.

Source: https://arxiv.org/abs/2509.22792

Product Assurance Quality Assurance for the LISA Mission

by Monica Scorța, ing

09.10.2025

Product Assurance (PA) and Quality Assurance (QA) are processes that aim to ensure compliance with specific applicable requirements and quality standards throughout the lifecycle of a space mission. The requirements can be perceived as the necessities that the persons in charge of the mission commit to fulfil for reaching its success. Key activities in the PA/QA processes include the establishment of clear quality goals (clear milestones to target), creation of processes and procedures to be followed by each team involved in a space mission, and implementation of preventive activities for continuous monitoring and assessment of the mission’s integrity and favourable outcome 

Like other standards used across industries (ISO manufacturing, healthcare, information technology, and ANSI - telecommunications, energy, finance), the ones used for the LISA Mission are the widely accepted ones used in the European space-missions framework, the ECSS (The European Cooperation for Space Standardization) standards. They approach thematics like Space Management, Space Engineering, and Space Sustainability, helping the involved teams in guiding themselves in the evolution process of the mission, from the very beginning, where the scene is set, the Conceptual Study, to the very end, the Disposal/Debris Mitigation.

Photo credit: https://ecss.nl/standards/

The ECSS documentation is formed by a series of Standards, Handbooks, and Technical Memoranda that address, in turn, requirements to be applied for each existing context of a space mission, additional information for the application of different standards, and non-normative but useful technical aspects to take into account. From these upper-level documents, there can be obtained the refined of, with the associated requirements, namely the so-called Tailored Requirements. These tailored requirements are a subset of the generic standards found in the ECSS documentation, aiming at addressing specific needs of the mission, in specific contexts, and reaching particular goals of the project.

Photo credit: https://ecss.nl/standards/ecss-tree/ 

LISA has its own Tailored Requirements that are followed by all the parties involved in the process of this mission’s realization. This user-friendly, single set of standards applied through the PA/QA activities is part of the LISA’s Product Assurance and Quality Assurance team’s activities, of whose members work in the ASPACE-Q group. There are these collective work and split responsibilities across the collaboration to ensure compliance with the ECSS standards and the Tailored Standards for the fulfilment of the mission.

Given the complexity of this endeavour, a planned approach to the necessary tasks to be fulfilled has always been the way to go in the context of space missions and not only. 

Other online resources:

• https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Onboard_Computers_and_Data_Handling/ECSS_standardization_Background
• https://ecss.nl/
• https://technology.esa.int/page/engineering-support-quality
• https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Product_Assurance

Eclipse in the Milky Way

by Alice Păun, PhD student

19.09.2025

Image courtesy of: Bureau of International Cooperation, Chinese Academy of Sciences

Although binary systems consisting of a pulsar and a helium star have been observed before, never until now has such a binary system been observed right in our own galaxy. In 2021, the FAST (Five-hundred-meter Aperture Spherical radio Telescope), during the “Galactic Plane Pulsar Snapshot survey”, observed an eclipse of the pulsar PSR J1928+1815.
At present, there is not yet a complete understanding of how these binary systems form and evolve. According to what we know, however, in a binary system of two stars, one of them tends to expand so that its atmosphere envelopes the other. As mass is transferred from one star to the other, their orbit shrinks over a period of approximately 1000 years, and the next stage is either that the two stars merge or, alternatively, that this atmosphere is ejected.

Considering the case observed with FAST, the binary system is composed of a star – neutron-star pair, and in these conditions, when the atmosphere is ejected, a helium star and a pulsar are formed. The latter is a neutron star that rotates rapidly and emits pulses in the radio band at a rate of hundreds of pulses per second. Thus, the helium star can eclipse the pulsar over the course of its orbit around it, causing “gaps” in its detection due to the shielding of the emitted radio signal. The time it takes for the two stars to complete one orbit around each other is 3.6 hours, and for 1/6 of this period, the pulsar is eclipsed and its signal cannot be detected.

Image source: Z. L. Yang et al. Science388,859-863(2025). DOI:10.1126/science.ado0769

Over time, this binary system evolves into a system made up of two compact objects that merge and generate a new source of gravitational waves.

Image source: Z. L. Yang et al. Science388,859-863(2025). DOI:10.1126/science.ado0769

References:

1.    Z. L. Yang et al., A pulsar-helium star compact binary system formed by common envelope evolution. Science388,859-863(2025). DOI:10.1126/science.ado0769

2.    https://physicsworld.com/a/short-lived-eclipsing-binary-pulsar-spotted-in-milky-way/

Researchers Detected Quantum Fluid of Electrons in Graphene

by Maria Ișfan, PhD student

12.09.2025

Top Left: 3D atomistic model of the graphene device. Bottom Left: Top view of the actual device, as seen under an optical microscope. Right: Artistic Illustration of electrons moving like a fluid inside graphene. Credit: Aniket Majumdar

Researchers at the Department of Physics, Indian Institute of Science (IISc), and collaborators from the National Institute for Material Science in Japan detected for the first time a quantum fluid of electrons in graphene (a material structure made of a single layer of carbon atoms). The results were published in Nature Physics (https://www.nature.com/articles/s41567-025-02972-z).

These electrons behave like a Dirac fluid. Instead of acting like individual quantum particles, they flow collectively as an ultra-low viscosity fluid. Usually, in a material the electrical and the thermal conductivities are proportional. However, in this electron fluid, they have an inverse relation, violating the Wiedermann-Franz law with a factor larger than 200 at low temperatures.

This exotic state of matter resembles the quark-gluon plasma, which is observed in particle accelerators at CERN.