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The Vera C. Rubin Observatory is releasing its first images on 23 June, showing us galaxies as we’ve never seen them before. Here’s how you can join a party to see those shots in full definition

Nucleosynthesis at the isotopic level: how chemical abundances enhance our understanding of globular clusters and dwarf galaxies

In the context of hierarchical galaxy assembly, both globular clusters and dwarf galaxies serve as indispensable probes of the formation of our Milky Way. The chemical composition of stars within these ancient structures plays a pivotal role in constraining their chemical enrichment history. To date, most studies have focused almost exclusively on elemental abundances, however, nucleosynthesis operates at the isotopic level. This talk will discuss how Mg isotope ratios shed light on both the accreted dwarf galaxy component of our Milky Way and the light element enhanced populations within globular clusters. This reveals contributions from supernova and low-mass stars that cannot be discerned through element abundances alone.

• Speaker: Madeleine McKenzie (Carnegie)
• Friday 20 June 2025, 11:30-12:30
• Venue: Ryle Seminar Room, KICC + online.
• Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

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arXiv:2506.13701v1 Announce Type: new Abstract: Gravitational instability (GI) is typically studied in cooling-dominated discs, often modelled using simplified prescriptions such as $\beta$-cooling. In this paper, we investigate the onset and evolution of GI in accretion discs subject to continuous mass injection, combining 1D and 3D numerical simulations. We explore an alternative self-regulation mechanism in which mass replenishment drives the system toward marginal stability $Q\sim 1$. In this regime, the disc establishes a steady-state disc-to-star mass ratio, balancing the mass transported to the central object with that added to the disc. Our 3D simulations reveal that the general scaling predicted from the linear theory are respected, however there are important difference compared to the cooling case in terms of morphology and pattern speed. Unlike the flocculent spirals seen in cooling-driven instability, the power is concentrated towards the dominant modes in infall-driven spirals. Additionally, spiral waves generate at the mass injection location, and propagate at constant pattern speed, unlike in the cooling case. This suggests a fundamental difference in how mass-regulated and cooling-regulated discs behave and transport angular momentum.

arXiv:2506.13701v1 Announce Type: new Abstract: Gravitational instability (GI) is typically studied in cooling-dominated discs, often modelled using simplified prescriptions such as $\beta$-cooling. In this paper, we investigate the onset and evolution of GI in accretion discs subject to continuous mass injection, combining 1D and 3D numerical simulations. We explore an alternative self-regulation mechanism in which mass replenishment drives the system toward marginal stability $Q\sim 1$. In this regime, the disc establishes a steady-state disc-to-star mass ratio, balancing the mass transported to the central object with that added to the disc. Our 3D simulations reveal that the general scaling predicted from the linear theory are respected, however there are important difference compared to the cooling case in terms of morphology and pattern speed. Unlike the flocculent spirals seen in cooling-driven instability, the power is concentrated towards the dominant modes in infall-driven spirals. Additionally, spiral waves generate at the mass injection location, and propagate at constant pattern speed, unlike in the cooling case. This suggests a fundamental difference in how mass-regulated and cooling-regulated discs behave and transport angular momentum.

arXiv:2506.12122v1 Announce Type: new Abstract: We present an extension of the pop-cosmos model for the evolving galaxy population up to redshift $z\sim6$. The model is trained on distributions of observed colors and magnitudes, from 26-band photometry of $\sim420,000$ galaxies in the COSMOS2020 catalog with Spitzer IRAC $\textit{Ch. 1}<26$. The generative model includes a flexible distribution over 16 stellar population synthesis (SPS) parameters, and a depth-dependent photometric uncertainty model, both represented using score-based diffusion models. We use the trained model to predict scaling relationships for the galaxy population, such as the stellar mass function, star-forming main sequence, and gas-phase and stellar metallicity vs. mass relations, demonstrating reasonable-to-excellent agreement with previously published results. We explore the connection between mid-infrared emission from active galactic nuclei (AGN) and star-formation rate, finding high AGN activity for galaxies above the star-forming main sequence at $1\lesssim z\lesssim 2$. Using the trained population model as a prior distribution, we perform inference of the redshifts and SPS parameters for 429,669 COSMOS2020 galaxies, including 39,588 with publicly available spectroscopic redshifts. The resulting redshift estimates exhibit minimal bias ($\text{median}[\Delta_z]=-8\times10^{-4}$), scatter ($\sigma_\text{MAD}=0.0132$), and outlier fraction ($6.19\%$) for the full $0

This NASA/ESA Hubble Space Telescope image features the barred spiral galaxy IC 758.ESA/Hubble & NASA, C. Kilpatrick

This serene spiral galaxy hides a cataclysmic past. The galaxy IC 758, shown in this NASA/ESA Hubble Space Telescope image, is situated 60 million light-years away in the constellation Ursa Major.

Hubble captured this image in 2023. IC 758 appears peaceful, with its soft blue spiral arms curving gently around its hazy barred center. However, in 1999, astronomers spotted a powerful explosion in this galaxy. The supernova SN 1999bg marked the dramatic end of a star far more massive than the Sun.

Researchers do not know exactly how massive this star was before it exploded, but will use these Hubble observations to measure the masses of stars in SN 1999bg’s neighborhood. These measurements will help them estimate the mass of the star that went supernova. The Hubble data may also reveal whether SN 1999bg’s progenitor star had a companion, which would provide additional clues about the star’s life and death.

A supernova represents more than just the demise of a single star — it’s also a powerful force that can shape its neighborhood. When a massive star collapses, triggering a supernova, its outer layers rebound off its shrunken core. The explosion stirs the interstellar soup of gas and dust out of which new stars form. This interstellar shakeup can scatter and heat nearby gas clouds, preventing new stars from forming, or it can compress them, creating a burst of new star formation. The cast-off layers enrich the interstellar medium, from which new stars form, with heavy elements manufactured in the core of the supernova.

Text Credit: ESA/Hubble

Image Credit: ESA/Hubble & NASA, C. Kilpatrick

More than 1200 studies using data from ESO’s facilities were published last year, a record high. This is the eighth consecutive year where observations conducted at ESO’s observatories have led to more than 1000 scientific publications. The ESO Library, Documentation, and Information Services Department has updated their detailed statistics on publications using ESO data presenting each facility's contributions in 2024 [1]. The data were presented to ESO Council earlier this month.  

As in previous years, the most productive ESO facilities continue to be the Very Large Telescope (VLT) and its interferometer (VLTI), which last year yielded data included in over 700 studies, a record high. VLT highlights include the observation of the awakening of a massive black hole at a galaxy’s core and the discovery of a planet orbiting Barnard’s star, the closest single star to our Sun, while the VLTI was used to take the first close-up picture of a star outside our galaxy. The Multi Unit Spectroscopic Explorer (MUSE) remains, by far, the most productive VLT instrument, producing data for a record 215 papers in 2024. Located at Paranal Observatory in Chile’s Atacama Desert, these facilities benefit from some of the world's best conditions for astronomy: pristine dark skies and clear nights. 

Also located at Paranal Observatory, the Visible and Infrared Telescope for Astronomy (VISTA) and the VLT Survey Telescope (VST) [2] contributed to 140 publications. A highlight from VISTA last year is the release of the most detailed infrared map ever of our Milky Way. Further south, the telescopes at ESO’s La Silla Observatory contributed to approximately 180 studies. 

The Atacama Large Millimeter/Submillimeter Array (ALMA), which is operated by ESO together with international partners, provided data for over 550 papers. Of these, about 50% papers used data obtained through observing time granted to astronomers based in Europe. A highlight includes the discovery of the most distant rotating disc galaxy. 

Until December 2022, ESO was also a partner of the Atacama Pathfinder Experiment (APEX) [3], located close to ALMA on the Chajnantor plateau in Chile’s Atacama region. In 2024, observations obtained during ESO observing time at APEX contributed to 38 papers, up from 24 the previous year. 

The 2024 publications statistics once again demonstrate the important legacy value of the ESO Science Archive Facility, with 42% of publications (510 papers) with ESO data partly or exclusively using archival data. For example, a study on the star-system HD 148937 that revealed its violent history used archival data from the FEROS instrument at ESO’s La Silla Observatory. Some 26% of papers relied on archival data alone, without any ESO observations obtained by the authors themselves. Even data from instruments that were decommissioned years ago still actively contributes to the pool of data papers.  

These record-breaking numbers underscore the vital role ESO's telescopes play in advancing humanity’s understanding of the Universe. This is made possible thanks to the work of the wider astronomical community and ESO staff, the advanced technology of ESO’s facilities, and the continued support of ESO’s member states and of Chile. 

Notes  

[1] Papers can use data from more than one facility, therefore the total number cannot be calculated by adding all publications of the individual sites.  

[2] The VST project was a joint venture between ESO and the Capodimonte Astronomical Observatory, part of the Italian National Institute for Astrophysics (INAF). As of 1 October 2022, this is a sole project of INAF, hosted by ESO at Paranal. Only papers based (entirely or partly) on ESO VST time are included in the statistics. 

[3] As of 1 January 2023, ESO hosts and operates APEX on behalf of the Max Planck Institute for Radio Astronomy.  

More Information  

The statistics presented here are derived from the ESO Telescope Bibliography (telbib), a database of refereed papers published by the ESO users community. Telbib is developed and curated by the ESO Library, Documentation, and Information Services Department. Whilst text-mining scripts are applied when screening the literature for ESO data papers, articles are carefully examined by the curators before they are added to the database to ensure that all telbib papers use partly or exclusively data from ESO facilities for which observing time was recommended by ESO. The public telbib interface provides visualisations of search results including on-the-fly graphs and predefined charts.  

The Proba-3 mission, consisting of two spacecraft that fly in close formation to study the sun, has returned images of the first ever artificial solar eclipse

There are new hints that the fabric of space-time may be made of "memory cells" that record the whole history of the universe. If true, it could explain the nature of dark matter and much more

Using machine learning to analyse data from the Event Horizon Telescope, researchers found the black hole at the centre of our galaxy is spinning almost as fast as possible

Streams: A New Frontier in Constraining Dark Matter Halo Populations

Tidal streams—remnants of disrupted stellar systems—are powerful tracers of galactic gravitational potentials. While streams in the Milky Way have yielded insights into its dark matter halo thanks to full 6D stellar data, applying this method to external galaxies is more difficult due to the lack of kinematics and projection effects. Individually, photometric-only streams offer limited constraints, but their collective signal can be statistically powerful.

In this talk, we present a novel hierarchical Bayesian framework that uses purely photometric data to constrain the population-level properties of dark matter halos. To achieve this, we constructed STRRINGS , a catalog of long and curved streams around nearby galaxies. Our results show that even without kinematic information, an ensemble of just 50 well-characterized streams can reliably distinguish between oblate, spherical, and prolate halos. This highlights that even purely photometric datasets, when analyzed in aggregate, can yield robust insights into dark matter distributions.

This breakthrough arrives at a critical moment, as upcoming surveys from Euclid and LSST are set to deliver an unprecedented volume of high-quality stream observations. Our approach represents a paradigm shift in how we constrain dark matter properties, ultimately refining our understanding of the universe’s fundamental structure.

• Speaker: David Chemaly / IoA
• Wednesday 18 June 2025, 13:15-13:40
• Venue: The Hoyle Lecture Theatre + Zoom .
• Series: Institute of Astronomy Seminars; organiser: .

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Streams: A New Frontier in Constraining Dark Matter Halo Populations

Tidal streams—remnants of disrupted stellar systems—are powerful tracers of galactic gravitational potentials. While streams in the Milky Way have yielded insights into its dark matter halo thanks to full 6D stellar data, applying this method to external galaxies is more difficult due to the lack of kinematics and projection effects. Individually, photometric-only streams offer limited constraints, but their collective signal can be statistically powerful.

In this talk, we present a novel hierarchical Bayesian framework that uses purely photometric data to constrain the population-level properties of dark matter halos. To achieve this, we constructed STRRINGS , a catalog of long and curved streams around nearby galaxies. Our results show that even without kinematic information, an ensemble of just 50 well-characterized streams can reliably distinguish between oblate, spherical, and prolate halos. This highlights that even purely photometric datasets, when analyzed in aggregate, can yield robust insights into dark matter distributions.

This breakthrough arrives at a critical moment, as upcoming surveys from Euclid and LSST are set to deliver an unprecedented volume of high-quality stream observations. Our approach represents a paradigm shift in how we constrain dark matter properties, ultimately refining our understanding of the universe’s fundamental structure.

• Speaker: David Chemaly / IoA
• Wednesday 18 June 2025, 13:15-13:40
• Venue: The Hoyle Lecture Theatre + Zoom .
• Series: Institute of Astronomy Seminars; organiser: .

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The Hubble Tension and Primordial Magnetic Fields

The Hubble tension hints at a missing ingredient in the standard cosmological model describing the universe around the epoch of recombination. A stochastic magnetic field, if present in the plasma prior to last scattering, would induce baryon inhomogeneities and speed up the recombination process, reducing the sound horizon at last scattering and potentially helping to relieve the Hubble tension. I will review this proposal and provide an update on its current status.

• Speaker: Levon Pogosian (Simon Fraser University)
• Monday 23 June 2025, 13:00-14:00
• Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
• Series: Cosmology Lunch; organiser: Louis Legrand.

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Hubble Studies a Spiral’s Supernova Scene This NASA/ESA Hubble Space Telescope image features the barred spiral galaxy IC 758. ESA/Hubble & NASA, C. Kilpatrick

This serene spiral galaxy hides a cataclysmic past. The galaxy IC 758, shown in this NASA/ESA Hubble Space Telescope image, is situated 60 million light-years away in the constellation Ursa Major.

Hubble captured this image in 2023. IC 758 appears peaceful, with its soft blue spiral arms curving gently around its hazy barred center. However, in 1999, astronomers spotted a powerful explosion in this galaxy. The supernova SN 1999bg marked the dramatic end of a star far more massive than the Sun.

Researchers do not know exactly how massive this star was before it exploded, but will use these Hubble observations to measure the masses of stars in SN 1999bg’s neighborhood. These measurements will help them estimate the mass of the star that went supernova. The Hubble data may also reveal whether SN 1999bg’s progenitor star had a companion, which would provide additional clues about the star’s life and death.

A supernova represents more than just the demise of a single star — it’s also a powerful force that can shape its neighborhood. When a massive star collapses, triggering a supernova, its outer layers rebound off its shrunken core. The explosion stirs the interstellar soup of gas and dust out of which new stars form. This interstellar shakeup can scatter and heat nearby gas clouds, preventing new stars from forming, or it can compress them, creating a burst of new star formation. The cast-off layers enrich the interstellar medium, from which new stars form, with heavy elements manufactured in the core of the supernova.

Text Credit: ESA/Hubble

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Media Contact:

Claire Andreoli (claire.andreoli@nasa.gov)
NASA’s Goddard Space Flight Center, Greenbelt, MD

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Details Last Updated Jun 13, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms

• Hubble Space Telescope
• Astrophysics
• Astrophysics Division
• Galaxies
• Goddard Space Flight Center
• Spiral Galaxies
• The Universe

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Earth’s magnetic field seems to correlate with conditions that helped complex life to thrive — a discovery that could aid the search for life on distant exoplanets.

There appears to be a volcano near Jezero crater on Mars and the Perseverance rover might already have samples from it that we could use to precisely date the activity of another planet's volcano for the first time

Title TBC

Abstract TBC

• Speaker: Dr. Manu Parra-Royón (IAA-CSIC)
• Tuesday 08 July 2025, 11:15-12:00
• Venue: TBC.
• Series: Hills Coffee Talks; organiser: Charles Walker.

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Science, Volume 388, Issue 6752, Page 1122-1123, June 2025.

With the ability to scan the entire southern night sky every three days, the huge Vera C. Rubin Observatory could be about to start solving the mysteries of the universe, from dark matter to Planet Nine

Impact of extragalactic point sources on the foregrounds and 21-cm observations

The contribution of resolved and unresolved extragalactic point sources to the low-frequency sky spectrum is a potentially non-negligible part of the astrophysical foregrounds for cosmic dawn 21-cm experiments. The clustering of such point sources on the sky, combined with the frequency dependence of the antenna beam, can also make this contribution chromatic. By combining low-frequency measurements of the luminosity function and the angular correlation function of extragalactic point sources, we develop a model for the contribution of these sources to the low-frequency sky spectrum. Using this model, we find that the contribution of sources with flux density >10^-6 Jy to the sky-averaged spectrum is smooth and of the order of a few kelvins at 50–200 MHz. We combine this model with measurements of the galactic foreground spectrum and weigh the resultant sky by the beam directivity of the conical log-spiral antenna planned as part of the Radio Experiment for the Analysis of Cosmic Hydrogen (REACH) project. We find that the contribution of point sources to the resultant spectrum is ∼ 0.4 per cent of the total foregrounds, but still larger by at least an order of magnitude than the standard predictions for the cosmological 21-cm signal. As a result, not accounting for the point-source contribution leads to a systematic bias in 21-cm signal recovery. We show, however, that in the REACH case, this reconstruction bias can be removed by modelling the point-source contribution as a power law with a running spectral index. We make our code publicly available as a python package labelled epspy.

• Speaker: Shikhar Mittal / Cavendish Laboratory
• Wednesday 18 June 2025, 13:40-14:05
• Venue: The Hoyle Lecture Theatre + Zoom .
• Series: Institute of Astronomy Seminars; organiser: .

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