Professor Joan Solà Peracaula, senior researcher at ICCUB, has been awarded the Universe Best Paper Award 2023 for his co-authored publication, “Running Vacuum in the Universe: Phenomenological Status in Light of the Latest Observations, and Its Impact on the σ₈ and H₀ Tensions.”

The award, granted annually by the journal Universe (MDPI), recognizes two outstanding papers—one research article and one review—published during the last two years.

The award-winning paper, co-authored by Adrià Gómez-Valent (ICCUB), Javier de Cruz Pérez (U. of Córdoba), and Cristian Moreno-Pulido (U. of Girona)—all former PhD students of Professor Joan Solà at the University of Barcelona—explores a new idea in cosmology called the Running Vacuum Model (RVM). This model offers a fresh way to think about dark energy, the mysterious force believed to be driving the accelerated expansion of the universe.  It is based on quantum field theoretical calculations in curved spacetime. The team tested this model using a wide range of the latest astronomical data, including observations on distant supernovae, the distribution of galaxies, and the cosmic microwave radiation left over from the Big Bang. The winning papers have been selected from a pool of 467 publications, based on scientific merit, originality, clarity, and impact, including citations and downloads.

What makes the RVM special is that it treats dark energy not as something fixed (such as the “cosmological constant”), but as something dynamical that evolves with time.  In addition, it treats dark energy as quantum vacuum energy, a fundamental concept. This helps explain some puzzling differences in current measurements of how fast the universe is expanding and how structures like galaxies grow. The model even suggests a new way the universe might have rapidly expanded in its earliest moments (i.e. a new model of inflation)—without needing assumptions about exotic particles called “inflatons”.  The idea of dynamical dark energy is very fashionable nowadays after the latest observations of the Dark Energy Spectroscopic Instrument (DESI). The RVM aligns with these observations and may provide a quantum field theoretical basis for them.

This award highlights the growing importance of RVM in helping scientists better understand the universe. The first comprehensive tests of the RVM suggesting the existence of dynamical dark energy were performed just 10 year ago (Astrophys.J.Lett. 811 (2015) L14).

As part of the recognition, the authors receive a 500CHF cash prize, a certificate, and a voucher to publish future research for free.
The full announcement by Universe can be viewed here, and the awarded paper is available here.

Reference

Solà Peracaula, J., Gómez-Valent, A., de Cruz Pérez, J., & Moreno-Pulido, C. (2023). Running Vacuum in the Universe: Phenomenological Status in Light of the Latest Observations, and Its Impact on the σ₈ and H₀ Tensions. Universe, 9(6), 262. https://doi.org/10.3390/universe9060262

The Solar Orbiter mission, a joint initiative between the European Space Agency (ESA) and NASA, has captured the first detailed images of the Sun’s south pole — a region previously unexplored. These groundbreaking observations were possible thanks to the spacecraft’s inclined orbit and its advanced instrumentation, which allows scientists to study the different layers of the solar atmosphere and measure the magnetic field at the Sun’s surface.
The Sun has a highly dynamic magnetic field that follows a cycle of approximately 11 years. During this period, solar activity — such as sunspots, solar flares, and coronal mass ejections — increases and decreases. At the midpoint of the cycle, a fascinating phenomenon occurs: the reversal of the Sun’s magnetic field polarity. This means that the magnetic north pole becomes south, and vice versa.

This process is neither instantaneous nor uniform. It begins with a reorganization of the magnetic field at mid-latitudes and eventually affects the poles. That’s why observing the Sun’s poles is key to understanding how this reversal happens and how it influences the Sun’s behavior and space weather.
The images reveal a “messy” magnetic field at the south pole, with both positive and negative polarities present. This phenomenon is linked to the fact that the Sun is currently at the peak of its activity cycle, a phase during which the polarity of its magnetic field reverses.
“The new data provided by Solar Orbiter give us more insight into how the Sun’s magnetic field polarity reversal occurs, especially in regions for which we previously had no data. This is crucial for improving current models of the solar activity cycle and, consequently, for enhancing long-term predictions of solar storms,” explains Dr. Àngels Aran, researcher of the Institute of Cosmos Sciences of the University of Barcelona and the Institute of Space Studies of Catalonia (ICCUB-IEEC).
 

The ICCUB-IEEC has played a key role in this scientific milestone. A team led by Dr. José Maria Gómez-Cama, ICCUB-IEEC researcher and member of the Department of Electronic and Biomedical Engineering at the University of Barcelona (UB), was responsible for developing and implementing the Image Stabilization System (ISS) of the PHI (Polarimetric and Helioseismic Imager) instrument. This system compensates for spacecraft motion to ensure high-quality imaging, such as the recent captures of the Sun’s south pole.

Additionally, the Heliospheric Physics and Space Weather group at ICCUB and the Department of Quantum Physics and Astrophysics has provided scientific support to the team behind the Energetic Particle Detector (EPD) instrument, developing models to predict particle radiation levels during solar storms — a key factor for mission safety.
Launched in February 2020, Solar Orbiter aims to study the Sun up close and from unique perspectives, particularly its poles, to better understand its magnetic behavior and its influence on the interplanetary environment. In the coming years, the spacecraft’s orbital inclination will gradually increase thanks to gravity-assist maneuvers around Venus. This will allow for even more detailed imaging of the solar poles, opening a new chapter in our understanding of the solar cycle and space weather.
 

A new international report has taken a major step toward understanding how some of the heaviest particles in the Universe behave in extreme conditions, similar to those just after the Big Bang. The team published their results in Physics Reports.
 

Physicists from the Indian Institute of Technology Goa, the Institute of Cosmos Sciences of the University of Barcelona (ICCUB), and Texas A&M University have published a comprehensive review exploring how particles containing heavy quarks (known as charm and bottom hadrons) interact in a hot, dense environment called hadronic matter. This environment is created in the last stage of high-energy collisions of atomic nuclei, such as those at the Large Hadron Collider (LHC) and the Relativistic Heavy Ion Collider (RHIC).

Recreating the Early Universe

When two atomic nuclei collide at near-light speeds, they generate temperatures over 100,000 times hotter than the center of the Sun. These collisions briefly produce a state of matter called the quark-gluon plasma (QGP), a soup of fundamental particles that existed microseconds after the Big Bang. As this plasma cools, it transitions into hadronic matter, a phase made up of particles like protons, neutrons, as well as other baryons and mesons. 

The study focuses on what happens to heavy-flavor hadrons (particles containing charm or bottom quarks, such as D and B mesons) during this transition and in the hadronic phase expansion that follows.

Heavy Particles as Probes

Heavy quarks are like tiny sensors. Because they are so massive, they are produced right after the initial nuclear collision and move more slowly and interact differently with the surrounding matter. By studying how they scatter and diffuse, we can learn about the properties of the medium they travel through.

The researchers reviewed a wide range of theoretical models and experimental data to understand how heavy hadrons, like D and B mesons, interact with light particles in the hadronic phase. They also examined how these interactions affect observable quantities like particle flow and momentum loss.

Key Findings

“To really understand what we see in experiments, it’s crucial to look at how heavy particles move and interact also during the later stages of these nuclear collisions,” said Dr. Juan M. Torres-Rincon. “This phase, when the system has cooled down, still plays a sizable role in shaping how particles lose energy and flow together. We also need to address the microscopic and transport properties of these heavy systems right at the transition point to the quark-gluon plasma. That’s the only way we can reach the level of precision that today’s experiments and simulations demand.”

To better understand these findings, one can use a simple analogy: imagine dropping a heavy ball into a crowded swimming pool. Even after the biggest waves settle, the ball keeps drifting and bumping into people. In a similar way, the heavy particles created in nuclear collisions continue to interact with other particles around them, even after the hottest and most chaotic phase has passed. These ongoing interactions subtly change how the particles move, and studying these changes helps scientists better understand the conditions of the early universe. Ignoring this phase would mean missing an important part of the story.

The study highlights the importance of including hadronic interactions in simulations to accurately interpret data from RHIC and LHC experiments.

Looking Ahead

Understanding how heavy particles behave in hot matter is crucial for mapping the properties of the early universe and the fundamental forces that govern it. The findings also pave the way for future experiments at lower energies, such as those planned at the CERN SPS and the upcoming FAIR facility in Darmstadt (Germany).

This work brings us closer to a complete picture of how matter behaves under extreme conditions and to answering some of the biggest questions about the origin of our Universe.

A study led by Paolo Padoan, research professor at the Institute of Cosmos Sciences at the University of Barcelona and currently on leave at Dartmouth College (USA), is challenging long-held beliefs about the formation of planetary disks around young stars. The research, which was published on April 21st in Nature Astronomy, reveals that the environment plays a crucial role in determining the size and lifespan of these disks, which are the birthplaces of planets.

When a star forms, it is surrounded by a spinning disk of gas and dust. Over time, this material coalesces into planets. Traditionally, scientists believed that once a disk forms, it simply loses mass over time as it fuels the growing star and planets. However, Dr. Padoan's research introduces a new perspective, showing that young stars actually gain mass from their surroundings through a process known as Bondi-Hoyle accretion. This process helps "refuel" the disk, making it larger and longer lasting than previously thought.

"Stars are born in groups or clusters inside large gas clouds and can remain in that environment for a few million years after their birth," said Dr. Padoan, first author of the study. " After a star is formed, its gravity can capture more material from the parental gas cloud, not enough to change the star’s mass significantly, but more than enough to restructure its disk. To understand how much mass a star can attract with this Bondi-Hoyle accretion, and the disk spin and size induced by the new material, we needed to model and understand some fundamental properties of the chaotic motion of the interstellar gas, known as turbulence. "

The study demonstrates that Bondi-Hoyle accretion can supply not only the mass but also the angular momentum necessary to explain the observed sizes of protoplanetary disks. This revised understanding of disk formation and evolution alleviates several longstanding observational discrepancies and compels substantial revisions to current models of disk and planet formation.
The research also addresses several puzzles in star and planet formation, such as why more massive stars have larger disks, why some planetary systems are unexpectedly massive, and why some disks last longer than expected. By shifting the focus from the star itself to the wider environment, this research provides a fresh perspective on the cosmic recipe for star and planet formation.

Dr. Padoan's team used advanced computer simulations and analytical modelling to explain the size of protoplanetary disks measured by ALMA, the world's most powerful radio telescope. The combination of theoretical models and empirical data provided a robust framework for understanding the complex interactions between young stars and their environments.

"Comparing the observable data from simulations to the actual observations is essential in validating the simulations, " said Dr. Veli-Matti Pelkonen, ICCUB researcher and member of the team. "However, simulations allow us to go beyond the observables to the underlying density, velocity and magnetic field structures, as well as following them in time. In this study, using the simulation data, we were able to show that the Bondi-Hoyle accretion plays an important part of the late-stage star formation, increasing the lifespan and the mass reservoir of the protoplanetary disks. With the increase of the computing power of supercomputers, we will be able to model even more complex physical processes in the simulations, further increasing the fidelity of the simulations. Combined with the new, powerful telescopes such as the James Webb Space Telescope and ALMA doing unparalleled observations of newly forming stars, these advances will continue to increase our understanding of star formation."

The implications of this study extend beyond just the formation of stars and planets. Understanding the role of the environment in disk formation could also shed light on the conditions necessary for the formation of habitable planets. This could have profound implications for the search for life beyond our solar system.

Reference: Padoan, P., Pan, L., Pelkonen, VM. et al. The formation of protoplanetary disks through pre-main-sequence Bondi–Hoyle accretion. Nat Astron (2025). https://doi.org/10.1038/s41550-025-02529-3 https://doi.org/10.1038/s41550-025-02529-3

We are thrilled to announce that the Institute of Cosmos Sciences of the University of Barcelona (ICCUB) has been accredited as a María de Maeztu Unit of Excellence in the 2024 Call by the Spanish Ministry of Science and Innovation. This prestigious recognition marks the third time ICCUB has been honored with the María de Maeztu accreditation, following its initial award in 2014. 

This distinction highlights organizations with highly competitive research programs that are among the best in the world in their respective scientific areas. The evaluation and selection process are conducted independently by an international scientific committee of widely recognized researchers, who select both Severo Ochoa centers and María de Maeztu units under the same rigorous criteria. ICCUB is one of the 17 organizations (9 Severo Ochoa centers and 8 María de Maeztu units) selected in this annual competitive call. 

"It is the third time the ICCUB has obtained the Maria de Maeztu award, not an easy feat," says Xavier Luri, director of the ICCUB. "It is not only an acknowledgement of the outstanding science produced by our researchers, but also of the long-term vision and the continuous search of excellence at the ICCUB. This award will allow us to expand our contributions to many key scientific challenges." 

The accreditation provides funding to research organizations that demonstrate international scientific impact and leadership, actively embrace knowledge transfer, and collaborate with the business sector. Efforts in open access policies to scientific publications, outreach, and knowledge diffusion are also recognized.  

The María de Maeztu recognition is valid for four years and provides more than 500.000€ annually. This funding will allow the ICCUB to realize its strategic Research Plan, attract scientific talent and foster our outreach and communication initiatives. 

"This award provides ICCUB the means to realize its ambitious scientific vision over the next 4 years," says Licia Verde, scientific director of the ICCUB. "To me this represents a strong vote of confidence in the quality and impact of past work and the potential of the institute to push the frontiers of the science of the cosmos. I am excited for what the next 4 years will bring. ICCUB team, our best work is yet to come!" 

As a Unit of Excellence, ICCUB will remain in the SOMM Excellence Alliance, which promotes Spanish Excellence in research and enhances its social impact at national and international levels. 

The Institute of Cosmos Sciences Strategic Plan 

The funding will be used to address several scientific challenges:  

• Exploring physics beyond the current standard models of particles and cosmology: This involves a coordinated approach that integrates theoretical modeling, precision measurements, and sophisticated data analysis techniques to uncover new physics. 

• Studying the physics involved in producing gravitational wave sources: By researching the origins and processes of gravitational wave events, ICCUB seeks to provide novel insights into the strong gravity regime and the nature of compact binary coalescences. This research will be supported by ICCUB's active participation in major collaborations and surveys, enhancing our understanding of the universe's constituents. 

• Exploiting quantum resources for science and technology: This includes advancing quantum communication, computation, and hardware development. The goal is to harness quantum entanglement and superposition to drive innovations in communication security and computational capacity, positioning ICCUB at the forefront of the second quantum revolution. 
   

In addition to these scientific endeavors, the funding will support various institutional activities, including:  

• Boosting recruitment strategies and talent acquisition with a focus on gender balance. 

• Providing comprehensive training programs for doctoral and postdoctoral researchers. 

• Expanding the Mental Health and resilience program. 

• Attracting diverse funding sources, fostering international leadership, and enhancing knowledge and technology transfer. 

• Prioritizing diversity, equity, and inclusion programs to ensure a supportive and inclusive environment. 

• Expanding outreach and communication efforts to new formats and activities to reach wider audiences, while increasing inclusivity by adapting materials and workshops. 

This recognition is a testament to the collective effort and unwavering commitment to excellence of all our researchers, as well as an inspiration for future scientific achievements. 

Awarded Severo Ochoa Centers and Maria de Maeztu units 

The centers and units that have received the María de Maeztu accreditation are: the Universitat Pompeu Fabra's Department of Medicine and Life Sciences, the Universidad de Barcelona's Institut de Ciències del Cosmos, the Universidade de Santiago de Compostela's CIMUS - Centro de Investigación en Medicina Molecular y Enfermedades Crónicas, the Universidad de Valencia's Instituto de Ciencia Molecular, the Fundación IMDEA Software's IMDEA Software Institute, the Fundación Privada Institut Català de Paleoecologia Humana i Evolució Social's Institut Català de Paleoecologia Humana i Evolució Social, the Universidad Autónoma de Barcelona's Institut de Ciencia i Tecnologia Ambientals (ICTA), and the Universidad de Sevilla's Instituto Universitario de Investigación de Matemáticas de la Universidad de Sevilla (IMUS). 

The Severo Ochoa accreditations have been awarded to: the Institut de Física d'Altes Energies, the Centro Nacional de Investigaciones Oncológicas Carlos III, the Instituto de Ciencia de Materiales de Madrid (ICMM), the Fundació Institut Català d'Investigació Química (ICIQ), the Barcelona Graduate School of Economics, the Instituto de Ciencias Fotónicas, the Fundación Donostia International Physics Center, the Instituto de Ciencias del Mar (ICM), and the Estación Biológica de Doñana (EBD). 

Acknowledgements
 

Grant CEX2024-001451-M funded by MICIU/AEI/10.13039/501100011033.

The 2025 Jocelyn Bell Burnell Inspiration Medal recognizes arXiv's significant contributions to astrophysical research through its open, free, and global distribution of scientific articles. Since its inception in 1991, arXiv has revolutionized the dissemination of scientific knowledge, breaking down barriers imposed by costly journals and championing open access by providing unrestricted access to all users.

Licia Verde, ICREA researcher and ICCUB's Scientific Director, will represent arXiv at the upcoming European Astronomical Society (EAS) award ceremony, where the organization will receive the prestigious Jocelyn Bell Burnell Inspiration Medal for its revolutionizing impact on astrophysical research. Verde, who has been an advisor to arXiv since 2016, will accept the award together with Ralph Wijer (University of Amsterdam) on behalf of the organization.

Licia Verde expressed her admiration for arXiv, stating, “Arxiv is an incredibly successful and inspiring story. To me it is an ideal (open science) that became a reality, and a community of researchers. Arxiv relies on a small, highly effective and extremely dedicated team and a much larger body of volunteers. I am honoured to have had the opportunity to contribute to this community in an advisory role, to the arXiv mission and to the global process of democratisation of knowledge."

This recognition highlights the international presence and impact of ICCUB researchers, showcasing their contributions to global scientific advancements. It also underscores ICCUB's commitment to open science, a principle that promotes transparency, accessibility, and the democratization of knowledge. By actively participating in initiatives like arXiv, ICCUB demonstrates its dedication to making scientific research more inclusive and equitable, ensuring that valuable knowledge is accessible to researchers worldwide, regardless of financial barriers.

As the leading open-access preprint repository for physics, astronomy, and related disciplines, arXiv plays a fundamental role in ensuring that scientific knowledge is rapidly disseminated, openly accessible, and freely available to all. This democratization of knowledge allows researchers from different institutions and countries to engage with the latest findings without financial barriers.

By fundamentally changing how astronomical knowledge is shared, arXiv exemplifies the spirit of the Jocelyn Bell Burnell Inspiration Medal, celebrating contributions that extend beyond traditional research to inspire and enable progress in astronomy and empower the global scientific community.
 

The European Space Agency (ESA) has powered down its Gaia spacecraft after more than a decade spent gathering data that are now being used to unravel the secrets of our home galaxy.

On 27 March 2025, Gaia’s control team at ESA’s European Space Operations Centre carefully switched off the spacecraft’s subsystems and sent it into a ‘retirement orbit’ around the Sun.

Though the spacecraft’s operations are now over, the scientific exploitation of Gaia’s data has just begun.

Gaia’s stellar contributions

aunched in 2013, Gaia has transformed our understanding of the cosmos by precisely mapping the positions, distances, motions, and properties of nearly two billion stars and other celestial objects. It has provided the largest, most precise multi-dimensional map of our galaxy ever created, revealing its structure and evolution in unprecedented detail.

The mission uncovered evidence of past galactic mergers, identified new star clusters, contributed to the discovery of exoplanets and black holes, mapped millions of quasars and galaxies, and tracked hundreds of thousands of asteroids and comets. The mission has also enabled the creation of the best visualisation of how our galaxy might look to an outside observer.

“Gaia’s extensive data releases are a unique treasure trove for astrophysical research, and influence almost all disciplines in astronomy,” says Gaia Project Scientist Johannes Sahlmann. “Data release 4, planned for 2026, and the final Gaia legacy catalogues, planned for release no earlier than the end of 2030, will continue shaping our scientific understanding of the cosmos for decades to come.”

Spanish institutions have had a major contribution to the mission. "The Gaia team at the University of Barcelona has been working on the mission since its inception around 1997." says Xavier Luri, director of the Institute of Cosmos Sciences of the University of Barcelona (ICCUB) and member of the Gaia UB team. "We have participated in all its phases, from defining the scientific case and industrial design to data processing and scientific exploitation. Now, although we say farewell to Gaia, several years of work remain to fully process all the data collected over these years and publish two additional data releases (DR4 and DR5)."

Saying goodbye is never easy

Gaia far exceeded its planned lifetime of five years, and its fuel reserves are dwindling. The Gaia team carefully considered how best to dispose of the spacecraft in line with ESA’s efforts to responsibly dispose of its missions.

They wanted to find a way to prevent Gaia from drifting back towards its former home near the scientifically valuable second Lagrange point (L2) of the Sun-Earth system and minimise any potential interference with other missions in the region.

“Switching off a spacecraft at the end of its mission sounds like a simple enough job,” says Gaia Spacecraft Operator Tiago Nogueira. “But spacecraft really don’t want to be switched off.”

“Gaia was designed to withstand failures such as radiation storms, micrometeorite impacts or a loss of communication with Earth. It has multiple redundant systems that ensured it could always reboot and resume operations in the event of disruption.”

“We had to design a decommissioning strategy that involved systematically picking apart and disabling the layers of redundancy that have safeguarded Gaia for so long, because we don’t want it to reactivate in the future and begin transmitting again if its solar panels find sunlight.”

On 27 March 2025, the Gaia control team ran through this series of passivation activities. One final use of Gaia’s thrusters moved the spacecraft away from L2 and into a stable retirement orbit around the Sun that will minimise the chance that it comes within 10 million km Earth for at least the next century. The team then safely deactivated and switched off the spacecraft’s instruments and subsystems one by one, before deliberately corrupting its onboard software. The communication subsystem and the central computer were the last to be deactivated.

Gaia’s final transmission to ESOC mission control marked the conclusion of an intentional and carefully orchestrated farewell to a spacecraft that has tirelessly mapped the sky for over a decade.

The final commands have been sent to Gaia. This is the last time that the spacecraft will ever hear from its team on Earth. The final commands include those to shut down the spacecraft's communication systems and central computer.
 

A lasting legacy

 

Though Gaia itself has now gone silent, its contributions to astronomy will continue to shape research for decades. Its vast and expanding data archive remains a treasure trove for scientists, refining knowledge of galactic archaeology, stellar evolution, exoplanets and much more.

A workhorse of galactic exploration, Gaia has charted the maps that future explorers will rely on to make new discoveries. The star trackers on ESA’s Euclid spacecraft use Gaia data to precisely orient the spacecraft. ESA’s upcoming Plato mission will explore exoplanets around stars characterised by Gaia and may follow up on new exoplanetary systems discovered by Gaia.

The Gaia control team also used the spacecraft’s final weeks to run through a series of technology tests. The team tested Gaia’s micro propulsion system under different challenging conditions to examine how it had aged over more than ten years in the harsh environment of space. The results may benefit the development of future ESA missions relying on similar propulsion systems, such as the LISA mission.

Forever in Gaia’s memory

 

The Gaia spacecraft holds a deep emotional significance for those who worked on it. As part of its decommissioning, the names of around 1500 team members who contributed to its mission were used to overwrite some of the back-up software stored in Gaia’s onboard memory.

Personal farewell messages were also written into the spacecraft’s memory, ensuring that Gaia will forever carry a piece of its team with it as it drifts through space.

As Gaia Mission Manager Uwe Lammers put it: “We will never forget Gaia, and Gaia will never forget us.”

The fate of the universe hinges on the balance between matter and dark energy: the fundamental ingredient that drives its accelerating expansion. New results from the Dark Energy Spectroscopic Instrument (DESI) collaboration use the largest 3D map of our universe ever made to track dark energy’s influence over the past 11 billion years. Researchers see hints that dark energy, once thought to be a “cosmological constant,” might be evolving over time in unexpected ways.
 

DESI is an international experiment with more than 900 researchers from over 70 institutions around the world and is managed by the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). The collaboration shared their findings today in multiple papers that will be posted on the online repository arXiv and in a presentation at the American Physical Society’s Global Physics Summit in Anaheim, California.

“The obtained results are very interesting”, says Andreu Font-Ribera, a scientist at the Institut de Física d’Altes Energies (IFAE) and a member of the DESI team that has developed this study. “It seems that we are on the verge of a change of paradigm for our models of the Universe, and this is very exciting”.

Taken alone, DESI’s data are consistent with our standard model of the universe: Lambda CDM (where CDM is cold dark matter and lambda represents the simplest case of dark energy, where it acts as a cosmological constant). However, when paired with other measurements, there are mounting indications that the impact of dark energy may be weakening over time and other models may be a better fit. Those other measurements include the light leftover from the dawn of the universe (the cosmic microwave background or CMB), exploding stars (supernovae), and how light from distant galaxies is warped by gravity (weak lensing).

“In my opinion, it is still too early to claim categorically that we have discovered an evolving dark energy”, says Eusebio Sánchez, scientific researcher at CIEMAT, who has participated in the data analysis. “However, the fact that different independent projects are observing similar results make this situation especially interesting”.

So far, the preference for an evolving dark energy has not risen to “5 sigma,” the gold standard in physics that represents the threshold for a discovery. However, different combinations of DESI data with the CMB, weak lensing, and supernovae sets range from 2.8 to 4.2 sigma. (A 3-sigma event has a 0.3% chance of being a statistical fluke, but many 3-sigma events in physics have faded away with more data.) The analysis used a technique to hide the results from the scientists until the end, mitigating any unconscious bias about the data.

“These new data could be indicating that the Universe is more complicated that we thought so far”, comments Sergi Novell Masot, PhD student at ICCUB and a member of the Institut d’Estudis Espacials de Catalunya (IEEC),  who has recently published a complementary study of the DESI maps. ”However, before obtaining final conclusions,  we need to understand the supernovae and CMB data that combined with DESI results seem to point towards this direction”.

DESI is one of the most extensive surveys of the cosmos ever conducted. The state-of-the-art instrument can capture light from 5,000 galaxies simultaneously.
 

Spanish groups had an important role in its construction and are collaborating in its operation. DESI is mounted on the U.S. National Science Foundation’s Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory in Arizona. The experiment is now in its fourth of five years surveying the sky, with plans to measure roughly 50 million galaxies and quasars (extremely distant yet bright objects with black holes at their cores) by the time the project ends.

The new analysis uses data from the first three years of observations and includes nearly 15 million of the best measured galaxies and quasars. It’s a major leap forward, improving the experiment’s precision with a dataset that is more than double what was used in DESI’s first analysis, which also hinted at an evolving dark energy.

“If it is confirmed, this would be one of the most important results in cosmology of the last few decades, since it opens the door to new ideas beyond the standard model, ΛCDM», comments Juan García-Bellido, a researcher at the IFT-UAM/CSIC, who has collaborated in this measurement. “If results get higher significance with future measurements we could explore ideas like new theories of gravitation or quintessence, that predict an evolving acceleration for the Universe expansion”.

DESI tracks dark energy’s influence by studying how matter is spread across the universe. Events in the very early universe left subtle patterns in how matter is distributed, a feature called baryon acoustic oscillations (BAO). That BAO pattern acts as a standard ruler, with its size at different times directly affected by how the universe was expanding. Measuring the ruler at different distances shows researchers the strength of dark energy throughout history. DESI’s precision with this approach is the best in the world.

“We are in an very exciting moment, since for a long time we thought the Universe behaves in a certain way, but now, with more precise data, we realize that there are aspects that we do not fully understand yet”, says Laura Casas, a PhD student at the Institut de Física d’Altes Energies (IFAE) in Barcelona, who has led the validation of the Lyman-alpha forest analysis, the imprint of intervening clouds of hydrogen in the light from distant quasars. “Although there is still much to research, the hints about evolving dark energy are a fascinating finding”.

The collaboration will soon begin work on additional analyses to extract even more information from the current dataset, and DESI will continue collecting data. Other experiments coming online over the next several years will also provide complementary datasets for future analyses. 

“The observational results we are obtaining about the evolution of the Universe open a wide spectrum for possible theories that can explain these observations”, comments Francisco Javier Castander, a researcher at the ICE-CSIC and IEEC, who has contributed to the experiment. “Independently of the dark energy nature, its properties will determine the Universe’s future. It is very rewarding to verify that the instrument we have built  allows us to make detailed observations of the sky, and then answer one of the biggest questions that humanity has ever asked”.

Videos discussing the experiment’s new analysis are available on the DESI YouTube channel. Alongside unveiling its latest dark energy results at the APS meeting today, the DESI collaboration also announced that its Data Release 1 (DR1) is now available for anyone to explore. With information on millions of celestial objects, the dataset will support a wide range of astrophysical research by others, in addition to DESI’s cosmology goals. 

The Dark Energy Spectroscopic Instrument Collaboration

DESI is supported by the DOE Office of Science and by the National Energy Research Scientific Computing Center, a DOE Office of Science national user facility. Additional support for DESI is provided by the U.S. National Science Foundation; the Science and Technology Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the French Alternative Energies and Atomic Energy Commission (CEA); the National Council of Humanities, Sciences, and Technologies of Mexico; the Ministry of Science and Innovation of Spain; and by the DESI member institutions.

The DESI collaboration is honored to be permitted to conduct scientific research on I’oligam Du’ag (Kitt Peak), a mountain with particular significance to the Tohono O’odham Nation.

The spanish institutions that participate in DESi are the Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), the Instituto de Ciencias del Espacio (ICE-CSIC/IEEC), the Institut de Ciències del Cosmos de la Universitat de Barcelona (ICCUB), the Institut de Física d'Altes Energies (IFAE), the Instituto de Física Teórica (IFT-UAM/CSIC), the Instituto de Astrofísica de Andalucía (IAA) and the Instituto de Astrofísica de Canarias (IAC).

Contact persons

CIEMAT: Dr. Eusebio Sánchez, Investigador Científico, eusebio.sanchez@ciemat.es
ICCUB-IEEC: Dr. Héctor Gil, Investigador Ramón y Cajal, hectorgil@icc.ub.edu
ICE-CSIC/IEEC: Dr. Francisco Castander, Profesor de Investigación, fjc@ice.csic.es
IFAE:    Dr. Andreu Font-Ribera, Investigador Ramón y Cajal, afont@ifae.es
IFT-UAM/CSIC: Dr. Juan García-Bellido, Catedrático, juan.garciabellido@uam.es

Distributed by the Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), the Institut de Ciències del Cosmos de la Universitat de Barcelona (ICCUB), the Instituto de Ciencias del Espacio (ICE-CSIC), the Institut d’Estudis Espacials de Catalunya (IEEC), the Institut de Física d’Altes Energies (IFAE) and the Instituto de Física Teórica (UAM-CSIC) on behalf of the DESI Collaboration.
 

An international research team with the participation of Núria Miret-Roig, researcher from the Institute of Cosmos Sciences of the University of Barcelona (ICCUB), has discovered that the Solar System traversed the Orion star-forming complex, a component of the Radcliffe Wave galactic structure, approximately 14 million years ago. This journey through a dense region of space could have compressed the heliosphere, the protective bubble surrounding our solar system, and increased the influx of interstellar dust, potentially influencing Earth's climate and leaving traces in geological records. The findings, published in Astronomy & Astrophysics, offer a fascinating interdisciplinary link between astrophysics, paleoclimatology, and geology.

The Solar System's journey around the Milky Way's center takes it through varying galactic environments. "Imagine it like a ship sailing through varying conditions at sea," explains Efrem Maconi, lead author and doctoral student at the University of Vienna. "Our Sun encountered a region of higher gas density as it passed through the Radcliffe Wave in the Orion constellation."

Using data from the European Space Agency's (ESA) Gaia mission and spectroscopic observations, the team pinpointed the Solar System's passage through the Radcliffe Wave in the Orion region about 14 million years ago. “We crossed the Orion complex while hundreds of stars were forming in that region, within  star clusters such as NGC 1977, NGC 1980, and NGC 1981,” says Núria Miret-Roig, a participant in the project and a current researcher of the University of Barcelona. “This is a very well-known region, visible with the naked eye in the winter sky of the Northern Hemisphere and the summer sky of the Southern Hemisphere”. 

"This discovery builds upon our previous work identifying the Radcliffe Wave," says João Alves, professor of astrophysics at the University of Vienna and co-author of the study. The Radcliffe Wave is a vast, thin structure of interconnected star-forming regions, including the renowned Orion complex, which the Sun traversed, as established in this study.

The increased dust from this galactic encounter could have had several effects. It may have penetrated the Earth's atmosphere, potentially leaving traces of radioactive elements from supernovae in geological records. "While current technology may not be sensitive enough to detect these traces, future advancements could make it possible," Alves suggests. 

The team's research indicates the Solar System's passage through the Orion region occurred between approximately 18.2 and 11.5 million years ago, with the most likely time between 14.8 and 12.4 million years ago. This timeframe aligns well with the Middle Miocene Climate Transition, a significant shift from a warm variable climate to a cooler climate, leading to the establishment of a continental-scale prototype Antarctic ice sheet configuration. While the study raises the possibility of a link between the past traverse of the solar system through its galactic neighborhood and Earth’s climate via interstellar dust, the authors emphasize that a causal connection requires further investigation. 

Not comparable to the current human-made climate change

“While the underlying processes responsible for the Middle Miocene Climate Transition are not entirely identified, the available reconstructions suggest that a long-term decrease in the atmospheric greenhouse gas carbon dioxide concentration is the most likely explanation, although large uncertainties exist. However, our study highlights that interstellar dust related to the crossing of the Radcliffe Wave might have impacted Earth’s climate and potentially played a role during this climate transition. To alter the Earth’s climate the amount of extraterrestrial dust on Earth would need to be much bigger than what the data so far suggest,” says Maconi. “Future research will explore the significance of this contribution. It’s crucial to note that this past climate transition and current climate change are not comparable since the Middle Miocene Climate Transition unfolded over timescales of several hundred thousand years. In contrast, the current global warming evolution is happening at an unprecedented rate over decades to centuries due to human activity.”
This study is important because it adds a small puzzle piece to the recent history of the Solar System, helping to place it in the context of the Milky Way. “We are inhabitants of the Milky Way,” says Alves, “The European Space Agency’s Gaia Mission has given us the means to trace our recent route in the Milky Way’s interstellar sea, allowing astronomers to compare notes with geologists and paleoclimatologists. It’s very exciting.” In the future, the team led by João Alves plans to study in more detail the Galactic environment encountered by the Sun while sailing through our Galaxy.

Reference: 
Maconi, E., J. Alves, C. Swiggum, S. Ratzenböck, J. Großschedl, P. Köhler, N. Miret-Roig, et al. “The Solar System’s Passage through the Radcliffe Wave during the Middle Miocene.” Astronomy & Astrophysics 694 (February 1, 2025): A167. https://doi.org/10.1051/0004-6361/202452061.
 

Traditional black holes -as predicted by Einstein's General Relativity- contain singularities, that is, points where the laws of physics break down. Identifying how singularities are resolved in the context of quantum gravity is one of the fundamental problems in theoretical physics. Now researchers from the Institute of Cosmos Sciences of the University of Barcelona (ICCUB) have described the creation of regular black holes purely from gravitational effects, without the need for exotic matter indicated by previous models.

This discovery, published in the journal Physics Letters B, offers a promising pathway towards understanding the quantum nature of gravity and the true structure of spacetime.

Black holes without singularities

Exotic matter refers to a type of matter that has unusual properties not found in ordinary matter. It often has a negative energy density, creating repulsive gravitational effects, and can violate certain energy conditions in general relativity. Exotic matter is largely theoretical and has not been observed in nature, but it is used in models to explore concepts like wormholes, faster-than-light travel, and resolution of black hole singularities.

The new study demonstrates that mathematically, an infinite series of higher-order gravitational corrections can eliminate these singularities, resulting in "regular" black holes. Unlike previous models that required exotic matter to achieve regular black holes, this research shows that pure gravity alone, with no additional matter fields, can produce these singularity-free solutions. This is a significant shift from earlier theories and simplifies the conditions needed for regular black holes.

“The beauty of our construction is that it only relies on modifications of the Einstein’s equations that are naturally predicted by quantum gravity. No other ingredients are required”, says Pablo Cano, from the Department of Quantum Physics and Astrophysics of the Faculty of Physics and the ICCUB.

The theories developed by the researchers are applicable in any spacetime dimension greater than or equal to five. “The reason for considering higher spacetime dimensions is purely technical” says Pablo Cano as it allows them to “reduce the mathematical complexity of the problem” - he adds. Nevertheless, the researchers expect that “the same conclusions should apply in our four dimensional spacetime”.

Moreover, the expert Robie Hennigar (UB-ICCUB) says that ”most scientists agree that the singularities of general relativity must be ultimately resolved, though we know very little about how this process could be accomplished. Our work provides the first mechanism to accomplish this in a robust way, albeit under certain symmetry assumptions.”

“It’s not clear how nature prevents the formation of singularities in our Universe, but we hope our model will help us to develop an understanding of this process” Says Henningar.

Exploring findings in astrophysical scenarios

The study also explores the thermodynamic properties of these regular black holes, showing that they satisfy the first law of thermodynamics. The theories developed by the researchers provide a robust framework for understanding black hole thermodynamics in a completely universal and unambiguous way. This consistency adds to the credibility and potential applicability of the findings.

The researchers plan to extend their work to four-dimensional spacetime and explore the implications of their findings in various astrophysical scenarios. They also aim to investigate the stability and potential observational signatures of these regular black holes.

“These theories not only predict singularity-free black holes, they also allow us to understand how these objects form and what is the fate of matter that falls inside a black hole. We are already working on these questions, finding really exciting results.” concludes Pablo Cano.

Reference article:

Bueno, Pablo; Cano, Pablo A; Hennigar, Robie A. «Regular black holes from pure gravity». Physics Letters B, February 2025. DOI: 10.1016/j.physletb.2025.139260