The documentary "Gaia: de casa nostra a l'Univers", produced by Big Van Ciència with the support of a grant from the Catalan Foundation for Research and Innovation (FCRI), highlights Catalonia’s key role in one of the most ambitious scientific missions in recent history: the Gaia mission of the European Space Agency (ESA).

Thanks to Gaia, humanity has been able to map nearly two billion stars in the Milky Way with unprecedented precision. A fundamental part of this success has been developed in Catalonia, with teams from the University of Barcelona (UB), the Institute of Space Studies of Catalonia (IEEC), and the Institute of Cosmos Sciences of the University of Barcelona (ICCUB) leading scientific contributions of top international level.

The premiere event will feature Teresa Sanchis, Director General for Research of the Government of Catalonia; Helena González, Director of Big Van Ciència; Xavier Luri, Full Professor in the Department of Quantum Physics and Astrophysics at the University of Barcelona, Director of the IEEC, and Principal Investigator of Gaia in Spain; Mercè Pallàs, Deputy for Coordination with UB Research Institutes; Maria Terrades, Director of the Barcelona Science Park; and Miquel Gómez, Director of the FCRI.

The event will combine institutional speeches, a screening of the documentary (35 minutes), and a science outreach show featuring humor and improvisation by Big Van Ciència, which will allow the audience to interact live with researchers from the Gaia mission.

The voice of Catalan science

“Gaia: de casa nostra a l'Univers” is not just a scientific documentary: it is a story about how research carried out in Catalonia is helping to transform global knowledge of our galaxy.

With more than 16,000 scientific publications derived from its data, Gaia has become a key tool for understanding the structure, origin, and evolution of the Milky Way. This documentary brings this scientific revolution closer to the general public, using an approachable and human tone, with touches of humor.

In the Gaia mission—the most ambitious project of the ESA to study the history and structure of the Milky Way—a team of astronomers and engineers from the Department of Quantum Physics and Astrophysics of the University of Barcelona, the ICCUB, and the IEEC has taken part since the very beginning, under the initial leadership of Professor Jordi Torra. Launched in 2013, the Gaia satellite has transformed our understanding of the cosmos through detailed stellar cartography of the positions, distances, motions, and properties of nearly two billion stars and other celestial objects.

Professor Xavier Luri highlights that “the UB Gaia team has worked on the mission since its beginnings, around 1997.” “Since then, it has taken part in all phases, from defining the scientific case and industrial design to data processing and scientific exploitation,” he continues. “Now, although Gaia has finished its observations, several years of work remain to fully process all the data collected during this period and to publish two additional data releases (DR4 and DR5),” the researcher concludes.

Black holes are often depicted as cosmic vacuum cleaners, but they are also powerful engines capable of launching jets: extremely fast streams of matter and energy shot out at nearly the speed of light. These jets strongly influence their surroundings, from nearby stars to entire galaxies. Yet one key question has remained unanswered: how powerful are these jets at any given moment?

A study published in Nature Astronomy has now achieved this long‑sought measurement by observing a jet that is quite literally bent sideways, and changing direction along the orbit.

The research focuses on the microquasar Cygnus X‑1, one of the most famous black holes in our Galaxy, located about 7,000 light‑years from Earth. The black hole orbits a massive, hot companion star that produces a powerful stellar wind — a constant stream of gas moving at thousands of kilometres per second.

Using almost 20 years of ultra‑sharp radio observations, the team discovered that this stellar wind pushes against the black hole’s jet, bending it as it travels through space. By modelling this interaction along the orbit, the researchers were able to directly calculate the jet’s power.

“The stellar wind acts like a natural probe,” explains Valentí Bosch‑Ramon, researcher at the Institute of Cosmos Sciences of the University of Barcelona (ICCUB) and co‑author of the study. “By measuring how much the jet bends and changes direction with time, we can determine how strong it really is.”

Reading a jet from its bend

An everyday analogy helps: a strong stream of water from a hose remains straight on a calm day but bends if the wind blows hard enough. In Cygnus X‑1, the same principle applies on cosmic scales.

Using a technique called Very Long Baseline Interferometry (VLBI) (which combines radio telescopes across the Earth) astronomers obtained images sharp enough to detect tiny changes in the jet’s direction during the black hole’s orbit. The jet always bends away from the companion star, leaving no doubt that the stellar wind is responsible.

From this bending, the team measured a jet power of about 10³⁷ ergs per second.

This is an enormous amount of energy, comparable to the system’s total X‑ray output and, over the age of the system, similar to the energy released by a supernova explosion.

(An “erg” is a unit of energy used in astrophysics; 10³⁷ ergs per second is trillions of trillions of times more powerful than human technologies can produce.)

Although Cygnus X‑1 hosts a relatively small black hole (about 20 times the mass of the Sun), the same physics applies to supermassive black holes at the centres of galaxies. Their jets are thought to regulate how galaxies grow — a process known as black‑hole feedback.

“This measurement gives strong observational support to assumptions used in galaxy‑formation models,” says Bosch‑Ramon. “Understanding a nearby system like Cygnus X‑1 helps us better understand the role of black holes across the Universe.”

Beyond this specific system, the study introduces a new way to measure jet power directly, turning a complex interaction into a powerful scientific tool.

“What used to be considered a complication for modelling this system,” Bosch‑Ramon adds, “has become a unique opportunity to measure one of the most extreme phenomena in astrophysics.”

Reference
Prabu, S. et al. A jet bent by a stellar wind in the black hole X‑ray binary Cygnus X‑1. Nature Astronomy (2026).
https://doi.org/10.1038/s41550-026-02828-3

The LISA mission has reached a key milestone in its development. The European Space Agency (ESA) has determined that the preliminary design of one of its subsystems—the Science Diagnostics Subsystem (SDS)—meets all mission requirements. This means ESA has given the green light to proceed to the detailed design phase, which will involve testing the system’s first prototypes.

Researchers from the Institute of Space Studies of Catalonia (IEEC) at the Institute of Space Sciences (ICE-CSIC) are leading the Spanish contribution to this project, providing their expertise to the development of the SDS instrument. The project also counts with the collaboration of the Institute of Cosmos Sciences of the University of Barcelona (ICCUB) and the company Sener. 
 

ICCUB develops the radiation monitor for LISA 
 

The ICCUB team, led by Daniel Guberman, is developing the radiation monitor, a particle detector designed to measure the ionizing radiation flux affecting the LISA Test Masses—one of the mission’s most critical components. Owing to its unique design and location, the Radiation Monitor is also expected to contribute to fields such as Space Weather and Solar Physics.

The instrument has been conceived and built entirely at ICCUB. A central figure in its development, Roger Català, led the design and implementation of both the electronics and mechanical systems, playing a key role in shaping the instrument. Andreu Sanuy also contributed his expertise to the electronic design, while Albert Espiña was responsible for the software and firmware.

The simulations and experimental validation with prototypes were led by Marina Orta, with contributions from Pierpaolo Loizzo (INFN and visiting research fellow at ICCUB) and Roberta Pillera (INFN), supporting the development and validation of the system. One of the key components of the Radiation Monitor is the BETA ASIC, also developed at ICCUB by a team led by David Gascón. 

From concept to validation 

The LISA (Laser Interferometer Space Antenna) mission will consist of three spacecraft separated by 2.5 million kilometres that will form a gravitational wave detector, the first to operate from space. Each of the spacecraft will house a mass in freefall in its interior, which will allow, through laser measurements between them, the detection of the effect of low-frequency gravitational waves (0.1 mHz – 1 Hz). The mission will allow for the study of phenomena such as the merger of massive black holes or compact systems in our galaxy, and will expand our vision of the universe.

The SDS is one of the primary components of the mission's payload led by Spain. In total, the SDS subsystem will put more than one hundred sensors into orbit to measure temperature, magnetic fields, and radiation. These will monitor environmental fluctuations from both the satellite and the interplanetary environment with extreme precision. Detecting gravitational waves requires measuring incredibly weak forces—on the order of the weight of a single bacterium. Therefore, the SDS’s role in distinguishing the effects of gravitational waves from environmental noise is critical to the mission’s success.

The successfully passed evaluation, called PDR (Preliminary Design Review), is the culmination of a process that formally began at the start of the year. The most decisive moment took place on 25 February, when the team travelled to the European Space Research and Technology Centre (ESTEC), ESA's technical offices in Noordwijk (Netherlands), to review and resolve the open points regarding this key mission system.

The LISA mission, led by ESA, receives funding from the Ministry of Science, Innovation and Universities of Spain through the Spanish Space Agency (AEE). 

Nadejda Blagorodnova Mujortova, a researcher at the Institute of Cosmos Sciences of the University of Barcelona, ​​the Institute of Space Studies of Catalonia (ICCUB-IEEC) and professor at the Faculty of Physics, has jointly received the 2025 National Research Award for Young Talent, with Katherine Villa Gómez, ICREA research professor and group leader at the Institute of Chemical Research of Catalonia (ICIQ). The announcement was made today by the Catalan Minister for Research and Universities, Núria Montserrat, at a press conference.

The award carries a €15,000 endowment, which is equally shared between the two awardees.

Nadejda Blagorodnova Mujortova's

research focuses on observational astronomy in the time domain, which studies transient astrophysical phenomena such as supernovae, stellar mergers, and stars disrupted by supermassive black holes.

With the research group Common Envelope Transients - Progenitors, Precursors, and Properties of their Outbursts (CET-3PO), funded by a grant from the European Research Council (ERC), she studies the interaction and merger of close binary stars. These studies combine stellar evolution models with observations from the most advanced ground-based telescopes, such as the Gran Telescopio Canarias, the Very Large Telescope (Chile), and the Southern African Large Telescope (South Africa), as well as observations Hubble Space Telescope and James Webb Space Telescope.

“I sincerely thank the Catalan Foundation for Research and Innovation for this recognition, which gives visibility to new generations of researchers. This award represents an incentive to continue working with passion and to reinforce research excellence and innovation,” says Blagorodnova.

Other awardees

The other categories of the National Research Awards were also announced today. Luis Serrano, director of the Centre for Genomic Regulation (CRG), has been awarded the 2025 National Research Award for his pioneering research in systems biology and protein design.

The National Research Award for Knowledge Transfer and Innovation went to the Eurecat Foundation, and the Joan Guinovart and Cirera Award for Science

Communication was given to biochemist and science communicator Pere Estupinyà. The National Award for Patronage and Public-private Scientific Collaboration has been given to the ARI Project, of Hospital Clínic and the August Pi i Sunyer Biomedical Research Institute (IDIBAPS), and the National Award for the Creation of a Science-based Company, was given to the University of Lleida and the University of Sherbrooke (Canada), for their start-up UniSCool.

That the universe is expanding has been known for almost a hundred years now, but how fast? The exact rate of that expansion remains hotly debated, even challenging the standard model of cosmology. A research team led by the Technical University of Munich (TUM), and with the participation of ICREA-ICCUB-IEEC researcher Frédéric Courbin, has now imaged and modelled an exceptionally rare supernova that could provide a new, independent way to measure how fast the universe is expanding.

The supernova is a rare superluminous stellar explosion, 10 billion lightyears away, and far brighter than typical supernovae. It is also special in another way: the single supernova appears five times in the night sky, like cosmic fireworks, due to a phenomenon known as gravitational lensing.

Two foreground galaxies bend the supernova’s light as it travels toward Earth, forcing it to take different paths. Because these paths have slightly different lengths, the light arrives at different times. By measuring the time delays between the multiple copies of the supernova, researchers can determine the universe’s present-day expansion rate, known as the Hubble constant.

Sherry Suyu, Associate Professor of Observational Cosmology at TUM and Fellow at the Max Planck Institute for Astrophysics, explains: “We nicknamed this supernova SN Winny, inspired by its official designation SN 2025wny. It is an extremely rare event that could play a key role in improving our understanding of the cosmos. The chance of finding a superluminous supernova perfectly aligned with a suitable gravitational lens is lower than one in a million. We spent six years searching for such an event by compiling a list of promising gravitational lenses, and in August 2025, SN Winny matched exactly with one of them.”

High-resolution color image of unique supernova

Because gravitationally lensed supernovae are so rare, only a handful of such measurements have been attempted to date. Their accuracy depends strongly on how well one can determine the masses of the galaxies acting as a lens, because these masses control how strongly the supernova’s light is bent. To measure those masses, the team obtained images with the Large Binocular Telescope in Arizona, USA, using its two 8.4-meter diameter mirrors and an adaptive optics system that corrects for atmospheric blurring. The result is the first high-resolution color image of this system published to date.

The observations reveal the two foreground lens galaxies in the center and five bluish copies of the supernova — reminiscent of a firework exploding. This is quite unusual, since galaxy-scale lens systems normally produce only two or four copies. Using the positions of all five copies, Allan Schweinfurth and Leon Ecker, junior researchers in the team, built the first model of the lens mass distribution.

“Until now, most lensed supernovae were magnified by massive galaxy clusters, whose mass distributions are complex and hard to model,” says Allan Schweinfurth. “SN Winny, however, is lensed by just two individual galaxies. We find overall smooth and regular light and mass distributions for these galaxies, suggesting that they have not yet collided in the past despite their close apparent proximity. The overall simplicity of the system offers an exciting opportunity to measure the universe’s expansion rate with high accuracy.”

ICCUB expertise in time-delay measurements

Frédéric Courbin has long been a leading figure in the field of time-delay cosmography. Courbin pioneered the field of time delay measurements in lensed quasars with the COSMOGRAIL program, which has provided some of the most precise measurements of the Hubble constant using gravitational lensing techniques.

His experience in long-term monitoring of gravitational lenses was instrumental in the present work. In particular, he organized the observations at the Maidanak Observatory, whose data have already been crucial in the past for monitoring lensed quasars and are now contributing to the study of this exceptional lensed supernova.

“It is particularly impressive to finally see a supernova lensed by a galaxy and with measurable delays. This will be done in the near future, in particular with Maidanak observations, which have already been crucial in the past for the observations of lensed quasars,” says Frédéric Courbin.

Two methods, two very different results

So far, scientists have mostly relied on two methods to measure the Hubble constant, but these methods yield conflicting results. This puzzle is known as the Hubble tension.

The first is the local method, which measures distances to galaxies one step at a time, much like climbing a ladder, where each step depends on the previous one; hence, it is referred to as the cosmic distance ladder. It uses objects with well-known brightness to estimate distances and then compares those distances with how fast galaxies are moving away. Because this method involves many calibration steps, even small errors can accumulate and affect the final result.

The second method looks much farther back in time. It studies the cosmic microwave background, the faint afterglow of the Big Bang, and uses models of the early universe to calculate today’s expansion rate. This approach is highly precise, but it relies heavily on assumptions about how the universe evolved, and these assumptions are still subject to debate.

A new, one-step approach

A third, independent method now enters the picture: using a gravitationally lensed supernova. Stefan Taubenberger, a leading member of Professor Suyu’s team and first author of the supernova-identification study, explains that by measuring the time delays between the multiple copies of the supernova and knowing the mass distribution of the lensing galaxy, scientists can directly calculate the Hubble constant: “Unlike the cosmic distance ladder, this is a one-step method, with fewer and completely different sources of systematic uncertainties.”

Astronomers worldwide are currently observing SN Winny in detail using both ground-based and space-based telescopes. Their results will provide crucial new insights and help clarify the long-standing Hubble tension.

Using the Atacama Large Millimeter/submillimeter Array (ALMA), an international team of astronomers, with the participation of ICCUB-IEEC researcher Gemma Busquet, has mapped a magnetic highway driving a powerful galactic wind into the nearby galaxy merger of Arp 220, revealing for the first time that its fast, molecular outflows are strongly magnetized and likely helping to drive metals, dust, and cosmic rays into the space around the galaxy. By watching how tiny dust grains and gas molecules line up with these fields, researchers have drawn the most detailed magnetic map yet of Arp 220’s buried, star‑forming cores and their outflows. The result is a new way to see how gravity, starbirth, black holes, and magnetic forces all work together in a chaotic cosmic environment. 
 

Arp 220 is an ultraluminous infrared galaxy (ULIRG) made up of two spiral galaxies in the final stages of merging. Because Arp 220 is the nearest galaxy of its kind, it serves as a powerful time machine: what happens here today likely mirrors what happened in the first generations of massive, dusty galaxies more than 10 billion years ago.
 

“We used ALMA to map the orientation and strength of magnetic fields in the twin galaxies,” shared Enrique Lopez-Rodriguez, the lead author of this research, and an Associate Professor with the University of South Carolina. “This revealed previously unseen details about Arp 220’s dust-enshrouded cores and molecular outflows, including the first detection of a polarized CO(3–2) molecular line emission,”  adds Josep Miquel Girart,  the lead in the observational work, and a researcher at the Institut de Ciències de l'Espai. This emission traced the galactic outflow in the external galaxy, showing that the outflowing gas itself carries a well-ordered magnetic field.
 

Observations of the west nucleus of Arp 220 revealed a nearly vertical magnetic field that runs alongside a bipolar molecular outflow moving at up to roughly 500 kilometers per second, driving a powerful, magnetic superhighway out of the galaxy. Galaxy mergers and starbursts are known to launch powerful winds that can shut down, or regulate, star formation by removing gas. However, these new results show that magnetic fields are a crucial, previously unknown driver in the force of these winds.

The team obtained full-polarization ALMA observations at 870 microns (Band 7), measuring both dust continuum polarization and CO(3–2) line polarization at a resolution of about 0.24 arcseconds (≈96 parsecs), fine enough to separate the two compact nuclei and their outflows. The dust polarization traces magnetically aligned grains in the cold, dense interstellar medium, while the Goldreich–Kylafis effect imprints linear polarization on the CO(3–2) emission line in the presence of anisotropic radiation and magnetic fields, together providing a three-dimensional view of the field geometry.

By combining the polarization geometry with measurements of gas mass, turbulence, and outflow speed, the authors applied and refined versions of the Davis–Chandrasekhar–Fermi method to estimate the magnetic field strengths in the blue- and redshifted outflow lobes. In the eastern nucleus, ALMA revealed a spiral-like magnetic pattern threading a compact, dust-enshrouded disk and arm, suggesting that ordered spiral fields can survive deep into the merger stage.

A highly polarized highway of dust between the two nuclei, with polarization fractions of about 3–5 percent, traces a magnetized ridge that may be funneling material and magnetic flux between the merging cores. Adds Lopez-Rodriguez, “When Arp 220 is observed as a whole, it’s one of the best places in the Universe for astronomers to study how gravity, star formation, and powerful winds work together with strong magnetic fields to reshape a galaxy and seed its surroundings with magnetized gas and dust.”

The team estimates magnetic field strengths of roughly 1–10 milligauss in the molecular outflows—hundreds to thousands of times stronger than the average magnetic field in the Milky Way’s disk—implying that compressed and turbulence-amplified fields help steer material into the circumgalactic medium. Because Arp 220 is the closest analog to the extreme, dusty star-forming galaxies in the early Universe, these results suggest that strong, organized magnetic fields may be common in high-redshift starbursts and could regulate star formation and feedback across cosmic time.

These ALMA observations show that magnetic fields are a major engine in driving material out of galaxies like Arp 220. The strong, ordered fields in its galactic winds act like invisible guardrails, guiding metals, dust, and cosmic rays into the vast cocoon of gas surrounding the system. That material will eventually help build and enrich future generations of stars and galaxies. As astronomers turn ALMA and future telescopes toward ever more distant galaxies, they expect to find similar magnetic superhighways at work across the cosmos. Studies like this transform Arp 220 from a single spectacular merger into a crucial blueprint for understanding how galaxies grow, shut down, and recycle their material over cosmic time—shaping the Universe we see today.

About NRAO
The National Radio Astronomy Observatory (NRAO) is a facility of the U.S. National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

About ALMA
The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Southern Observatory (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.
 

Researchers from the Institute of Cosmos Sciences of the University of Barcelona (ICCUB) and the Institute of Space Studies of Catalonia (IEEC), in collaboration with the Instituto de Astrofísica de Canarias (IAC), have led the largest observational study ever conducted on massive runaway stars including rotation and binarity in our Galaxy. This work, recently published in Astronomy & Astrophysics, sheds light on how these stellar “fugitives” are launched into space and what their properties reveal about their intriguing origins.

Runaway stars are stars that travel through space at unusually high speeds, moving away from the sites where they were born. The way that  massive runaway stars acquired their high speeds have long puzzled astronomers that considered two scenarios: a powerful push when a companion explodes as a supernova in a binary system, or a gravitational ejection during close encounters in dense and young star clusters. However, the relative contribution of these scenarios to understand massive runaway stars were not well constrained in the Milky Way.

Using data from Gaia, a space observatory from the European Space Agency (ESA), and high-quality spectroscopic information from the IACOB project, the team analyzed 214 O-type stars, which are the most massive and luminous stellar objects in the Galaxy. They combined measurements of rotation speed and binarity (whether the star is single or part of a binary system) for the largest sample of Galactic O-type runaway stars to understand their origins. 

The results show that most runaway stars rotate slowly, but those that rotate faster are more likely linked to supernova explosions in binary systems. The fastest-moving stars tend to be single, suggesting they were ejected from young clusters through gravitational interactions. Interestingly, they found that there are almost no runaway stars that move fast and rotate fast, highlighting potential distinct formation pathways. The researchers also identified twelve runaway binary systems, including three known high-mass X-ray binaries (systems that host neutron stars or black holes), and three other binaries that are promising candidates to host black holes.

Massive runaway stars are not just curiosities, they influence the evolution of galaxies. By escaping their birthplaces, they spread heavy elements and radiation across the interstellar medium, shaping future generations of stars and planets. Understanding their origins helps refine models of stellar evolution, supernova explosions, and even the formation of gravitational wave sources. In this context, this work serves as a benchmark for the next generation of massive binary stellar evolution models and cluster dynamical studies.

“This is the most comprehensive observational study of its kind in the Milky Way,” says Mar Carretero-Castrillo, lead author of the study who is now based at the European Southern Observatory. “By combining rotation and binarity information, we provide the community with unprecedented constraints on how these stellar runaways form.”

Future data releases from Gaia and ongoing spectroscopic surveys will allow astronomers to expand these samples and trace the past trajectories of runaway stars, linking them to their birth places. This will help confirm which formation mechanisms dominate and uncover new candidates for exotic systems like high-energy binaries hosting neutron stars or black hole companions.
 

Reference:

https://ui.adsabs.harvard.edu/abs/2025arXiv251021577C/abstract

A&A: https://www.aanda.org/10.1051/0004-6361/202556646

DOI: https://doi.org/10.1051/0004-6361/202556646

Contact:

Mar Carretero-Castrillo mcarrete@eso.org

An international team of scientists led by the Institute of Cosmos Sciences of the University of Barcelona and the Institute of Space Studies of Catalonia (ICCUB-IEEC) have introduced REGALADE, an unprecedented all-sky catalog that brings together nearly 80 million galaxies. This achievement, now published in the prestigious journal Astronomy & Astrophysics (A&A), marks a turning point for astronomy, enabling researchers to explore cosmic events with a level of precision never seen before.

When a telescope detects a sudden phenomenon such as a supernova or the merger of two black holes or neutron stars, astronomers need to know where to look and how far away the event occurred. That requires identifying the galaxy hosting the event. Until now, existing catalogs were incomplete beyond about 300 million light-years, leaving large gaps in our map of the nearby Universe. REGALADE fills those gaps by combining data from major surveys and cleaning it using data from the Gaia mission to remove stars mistakenly classified as galaxies. The result is a high-purity, high-completeness catalog that includes accurate distances and size measurements for all galaxies, and stellar masses for most. 

“REGALADE began as a user experience problem: astronomers relied on many popular catalogs, but each one covered only part of the sky or lacked key information,” explains Hugo Tranin, ICCUB researcher and lead author of the study. “By merging data from 14 widely used catalogs and deep imaging surveys, we now have a single, unified place to look for galaxy distances and properties. This drastically simplifies the daily work of astronomers and allows our team to retrieve distances for more than 75% of the transients reported worldwide every day.” The team has also released an interactive sky viewer (https://blackpearl.blackgem.org/regalade.php), where the public can explore the REGALADE catalog and navigate millions of galaxies in just a few clicks.

The scale and depth of REGALADE are extraordinary. It covers the entire sky and reaches out to more than four billion light-years, mapping about 10% of the volume of the observable Universe. This completeness means astronomers can now identify many more host galaxies for all types of cosmic events, from infrared to X-rays, and significantly improve strategies for gravitational-wave follow-up. According to Nadia Blagorodnova, ICCUB-IEEC researcher and co-author, “Observatories like the Vera Rubin Observatory will detect millions of cosmic events every night. REGALADE ensures we can identify their host galaxies quickly and accurately, enabling rapid classification of rare transients such as luminous red novae, stellar mergers that our team actively studies, and opening the door to the discovery of entirely new types of celestial phenomena.”

The study was led by Hugo Tranin, researcher at the Institute of Cosmos Sciences of the University of Barcelona (ICCUB), with the participation of ICCUB-IEEC researchers Nadejda Blagorodnova, Marco A. Gómez-Muñoz and Maxime Wavasseur. Their work combines expertise in time-domain astronomy, galaxy surveys and multi-messenger astrophysics, positioning the ICCUB team at the forefront of efforts to build comprehensive resources for the next generation of observatories.

Reference: 

Tranin, H., Blagorodnova, N., Gómez‑Muñoz, M. A., Wavasseur, M., Groot, P. J., Landsberg, L., Stoppa, F., Bloemen, S., Vreeswijk, P. M., Pieterse, D. L. A., van Roestel, J., Scaringi, S., Faris, S.,et al. (2025). A catalog to unite them all: REGALADE, a revised galaxy compilation for the advanced detector era. [Article]. Astronomy & Astrophysics. https://doi.org/10.1051/0004-6361/202556896

A new study led by researchers at the Institute of Cosmos Sciences of the University of Barcelona (ICCUB) and the Centre national de la recherche scientifique (CNRS) offers fresh insights into how galaxies like our Milky Way form and evolve and why their stars show surprising chemical patterns.

Published in Monthly Notices of the Royal Astronomical Society, the research explores the origins of a puzzling feature in the Milky Way: the presence of two distinct groups of stars with different chemical compositions, known as the “chemical bimodality.”

What is chemical bimodality?

When scientists study stars near the Sun, they find two main types based on their chemical makeup, specifically, the amounts of iron (Fe) and magnesium (Mg) they contain. These two groups form separate “sequences” in a chemical diagram, even though they overlap in metallicity (how rich they are in heavy elements like iron). This has long puzzled astronomers.

The new study uses advanced computer simulations (called the Auriga simulations) to recreate the formation of galaxies like the Milky Way in a virtual universe. By analyzing 30 simulated galaxies, the team looked for clues about how these chemical sequences form.

Understanding the chemical history of the Milky Way helps scientists piece together how our Galaxy, and others like it, came to be. This includes our sister galaxy, Andromeda, in which no bimodality has yet been detected. It also provides clues about the conditions in the early universe and the role of cosmic gas flows and galaxy mergers.

“This study shows that the Milky Way’s chemical structure is not a universal blueprint,” says lead author Matthew D. A. Orkney, researcher at ICCUB and the Institut d’Estudis Espacials de Catalunya (IEEC). “Galaxies can follow different paths to reach similar outcomes, and that diversity is key to understanding galaxy evolution.”

Key findings
 

The study reveals that galaxies like the Milky Way can develop two distinct chemical sequences through various mechanisms. In some cases, this bimodality arises from bursts of star formation followed by periods of little activity, while in others it results from changes in the inflow of gas from the galaxy’s surroundings. Contrary to previous assumptions, the collision with a smaller galaxy known as Gaia-Sausage-Enceladus (GSE) is not a necessary condition for this chemical pattern to emerge. Instead, the simulations show that metal-poor gas from the circumgalactic medium (CGM) plays a crucial role in forming the second sequence of stars. Moreover, the shape of these chemical sequences is closely linked to the galaxy’s star formation history.

As new telescopes like the James Webb Space Telescope (JWST) and upcoming missions such as PLATO and Chronos provide more detailed data on stars and galaxies, researchers will be able to test these findings and refine our picture of the cosmos.

“This study predicts that other galaxies should exhibit a diversity of chemical sequences. This will soon be probed in the era of 30m telescopes where such studies in external galaxies will become routine. Ultimately, these will also help us further refine the physical evolutionary path of our own Milky Way,” adds Chervin Laporte (ICCUB-IEEC, CNRS-Observatoire de Paris and Kavli IPMU). 

Participating Institutions

This research has been led by researchers from the Institute of Cosmos Sciences of the University of Barcelona (ICCUB), the Institute of Space Studies of Catalonia (IEEC) and the CNRS with the collaboration of scientists from Liverpool John Moores University and the Max-Planck-Institut für Astrophysik.

 

Reference:

Orkney, M. D. A., et al. (2025). The Milky Way in context: The formation of galactic discs and chemical sequences from a cosmological perspective. Monthly Notices of the Royal Astronomical Society. https://doi.org/10.1093/mnras/staf1551