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The Messenger is ESO’s journal for science and technology. It serves as a link between ESO and its broad astronomical community by providing information about scientific, technical, and other developments. It also delivers relevant news about astronomy and astrophysics to a broader public, including policy-makers, government officials, journalists, teachers, and amateur astronomers, as well as to interested scientists from other fields.

The Messenger is published twice per year and is available for free download as a PDF here and via the digital publishing platform Scribd.

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Latest Issue
Messenger Issue 194

The Messenger Issue 194

Highlights include:

  • Doyon, R., Bouchy, F. et al.: NIRPS Joins HARPS: Setting New Standards at Infrared Wavelengths
  • Nazari, P., Jerabkova, T. et al.: Usage of Artificial Intelligence by ESO Telescope Users
  • De Breuck, C., Díaz Trigo, M.: Report on the ESO workshop "The Promises and Challenges of the ALMA Wideband Sensitivity Upgrade"

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Messenger Issue 193
2024Issue 193
Messenger Issue 192
2024Issue 192
Messenger Issue 191
2023Issue 191
Messenger Issue 190
2023Issue 190
Messenger Issue 189
2022Issue 189
Messenger Issue 188
2022Issue 188
Messenger Issue 187
2022Issue 187
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2019Issue 178
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2019Issue 176
Messenger Issue 175
2019Issue 175
Table of Content No. 194 | 2025
Astronomical Science
Fahrion, K., Lyubenova, M.
Exploring the Star Clusters in the Centres of Galaxies with MUSE
More...
ADS BibCode: 2025Msngr.194....5F
Authors:
Fahrion, K., Lyubenova, M.
Abstract:
Massive star clusters are ubiquitous in the central regions of galaxies. For example, nuclear star clusters are present in most galaxies, and bulge regions can host globular clusters. Even though these star clusters are bright, studying their properties is limited by the underlying galaxy light. Here we discuss how integral-field spectroscopy with the Multi Unit Spectroscopic Explorer (MUSE) has enabled studies of the inner globular cluster systems of massive galaxies and how MUSE has allowed us to constrain the formation mechanisms of nuclear star clusters.

Page 5-7 (PDF)
Hammer, F., Bonifacio, P. et al.
Young Stars Discovered in Dwarf Spheroidal Galaxies Confirm their Recent Infall into the Milky Way
More...
ADS BibCode: 2025Msngr.194....8H
Authors:
Hammer, F., Bonifacio, P., Caffau, E., Yang, Y., Arenou, F., Babusiaux, C., Spite, M., François, P., Gomez, A., Katz, D., Monaco, L., Pawlowski, M., Wang, J.
Abstract:
Recent observations from ESA’s Gaia satellite and with ESO’s Very Large Telescope have identified the presence of a population of young stars, 0.5 to 2 Gyr old, in the halo of, and in dwarf spheroidal galaxies surrounding, the Milky Way (MW). It suggests that MW dwarf galaxies, currently devoid of gas, had, until recent times, enough gas to sustain a burst of star formation. The recent loss of gas coincides with their arrival in the vicinity of the MW, in agreement with orbital predictions from Gaia that indicate that most dwarf galaxies reached the MW halo less than 3 Gyr years ago. This completely changes the interpretation of their dynamics, mass and dark matter content.

Page 8-11 (PDF)
Telescopes and Instrumentation
Doyon, R., Bouchy, F. et al.
NIRPS Joins HARPS: Setting New Standards at Infrared Wavelengths
More...
ADS BibCode: 2025Msngr.194...13D
Authors:
Doyon, R., Bouchy, F., Pepe, F., Melo, C., Artigau, É., Malo, L., Wildi, F., Baron, F., Delfosse, X., Renan De Medeiros, J., González Hernández, J., Santos, N., Wade, G., Allart, R., Al Moulla, K., Blind, N., Cadieux, C., Canto Martins, B., Cook, N., Dumusque, X., Frensch, Y., Genest, F., Grieves, N., Lo Curto, G., Lovis, C., Mignon, L., Nielsen, L., Poulin-Girard, A., Rasilla, J., Rebolo, R., Reshetov, V., Sosnowska, D., Sordet, M., Saint-Antoine, J., Suárez Mascareño, A., Thibault, S., Vallée, P., Vandal, T., Abreu, M., Aguiar, J., Allain, G., Arial, T., Auger, H., Barros, S., Bazinet, L., Benneke, B., Bonfils, X., Boucher, A., Bourrier, V., Bovay, S., Broeg, C., Brousseau, D., Bruniquel, V., Bryan, M., Cabral, A., Carmona, A., Carteret, Y., Challita, Z., Chazelas, B., Cloutier, R., Coelho, J., Cointepas, M., Conod, U., Cowan, N., Cristo, E., Gomes da Silva, J., Dauplaise, L., Darveau-Bernier, A., de Lima Gomes, R., Brito de Freitas, D., Delgado-Mena, E., Delisle, J., Ehrenreich, D., Faria, J., Figueira, P., Fontinele, D., Forveille, T., Gagné, J., Genolet, L., Gracia Témich, F., Hernandez, O., Hobson, M., Hoeijmakers, J., Hubin, N., Jahandar, F., Jayawardhana, R., Käufl, H., Kerley, D., Kolb, J., Krishnamurthy, V., Lafrenière, D., Lamontagne, P., Larue, P., Leath, H., L’Heureux, A., de Castro Leão, I., Lim, O., Martins, A., Matthews, J., Mayer, J., Messias, Y., Metchev, S., Moranta, L., Mordasini, C., Mounzer, D., Nari, N., Osborn, A., Ouellet, M., Otegi, J., Parc, L., Pasquini, L., Passegger, V., Pelletier, S., Peroux, C., Piaulet-Ghorayeb, C., Plotnykov, M., Pompei, E., Rowe, J., Sarajlic, M., Segovia, A., Seidel, J., Ségransan, D., Schnell, R., Costa Silva, A., Srivastava, A., Stefanov, A., Teixeira, M., Udry, S., Valencia, D., Vaulato, V., Wardenier, J., Wehbe, B., Weisserman, D., Wevers, I., Yariv, V., Zins, G.
Abstract:
The Near-InfraRed Planet Searcher (NIRPS) is a high-resolution, near-infrared spectrograph optimised for detecting and characterising exoplanets around low-mass stars, working in tandem with the High Accuracy Radial velocity Planet Searcher (HARPS). While HARPS set new standards 20 years ago with its metre-per-second-level precision, NIRPS follows this successful path, achieving even better precision at infrared wavelengths. This article presents an overview of the design of NIRPS, its on-sky performance, its Guaranteed Time Observation programme, and its first scientific results.

Page 13-18 (PDF)
Jones, M.
Optimisation of the SPHERE Adaptive Optics Setup at ~11 mag
More...
ADS BibCode: 2025Msngr.194...19J
Authors:
Jones, M.
Abstract:
We have extended the recent analysis of the SPHERE adaptive optics (AO) performance for faint stars. In particular, we compared the raw contrast reached using the medium-frequency (600 Hz) and low-frequency (300 Hz) modes on different targets with G > 11 mag, and under different atmospheric conditions. We found that using the medium-frequency mode in this magnitude range leads to significantly better contrast. Based on these results, we have updated the AO frequency setup accordingly, that is, we extended the 600 Hz mode by one magnitude, up to 11.5 mag.

Page 19-20 (PDF)
Santos, N., Cabral, A. et al.
PoET: the Paranal solar ESPRESSO Telescope
More...
ADS BibCode: 2025Msngr.194...21S
Authors:
Santos, N., Cabral, A., Leite, I., Smette, A., Abreu, M., Alves, D., Martins, J., Monteiro, M., Silva, A., Wehbe, B., Arancibia, J., Ávila, G., Brillant, S., Cárdenas, C., Clara, R., Gafeira, R., Gaytan, D., Lovis, C., Miranda, N., Moreno, P., Oliveira, A., Otarola, A., Pepe, F., Rojas, P., Schmutzer, R., Sosnowska, D., van der Heyden, P., Al Moulla, K., Adibekyan, V., Barka, A., Barros, S., Branco, P., Cristo, E., Damasceno, Y., Demangeon, O., Dethier, W., Faria, J., Gomes da Silva, J., Gonçalves, E., Lucero, J., Rodrigues, J., San Nicolas Martinez, C., Santos, Â., Sousa, S., Viana, P.
Abstract:
The detection and characterisation of other ‘Earths’, orbiting other suns, is a bold objective of present-day astrophysics. However, this quest is severely challenged by astrophysical ‘noise’ from the host stars, whose signatures distort the observed spectra. Motivated by this problem, we are building a dedicated facility, the Paranal solar ESPRESSO Telescope (PoET). PoET will collect solar light and channel it into the ESPRESSO spectrograph, allowing us to use the Sun as a proxy to unambiguously identify and understand the sources of relevant variability in solar-type stars.

Page 21-25 (PDF)
Moehler, S., Freudling, W.
Flux Calibration for VLT and ELT Spectrographs
More...
ADS BibCode: 2025Msngr.194...26M
Authors:
Moehler, S., Freudling, W.
Abstract:
ESO offers a range of optical and infrared spectrographs on its telescopes, and more will be available once ESO’s Extremely Large Telescope (ELT) starts operating. Some, but not all, science cases require the flux of spectra to be calibrated in relative or absolute units. The achievable accuracy of such a flux calibration differs with circumstances and instrument. In this article, we provide an overview of the methods and routinely obtained accuracy for current Very Large Telescope and future ELT spectrographs.

Page 26-30 (PDF)
Astronomical News
Jerabkova, T., Patat, F. et al.
Distributed Peer Review at ESO: Demonstrating Success and Evolving Through Period 115
More...
ADS BibCode: 2025Msngr.194...33J
Authors:
Jerabkova, T., Patat, F., Dorigo, D., Sogni, F., Primas, F., De Cia, A., Hoppe, E.
Abstract:
ESO’s Distributed Peer Review (DPR) has transformed proposal evaluations by fostering efficiency and community involvement, making it an essential tool for handling the large volume of proposals traditional panels cannot review alone. A key strength of DPR is its inclusion of the entire community, engaging researchers at all career levels and identifying expert reviewers. This article summarises updated findings up to Period 115, focusing on expertise assignment, DPR comment usefulness and user satisfaction. DPR’s success supports its planned expansion into fast-track channels and yearly cycles. ESO is also exploring further innovations to optimise this process.

Page 33-36 (PDF)
Hilker, M., Kuntschner, H.
ESO’s Scientific Visitor Programme in Garching
More...
ADS BibCode: 2025Msngr.194...37H
Authors:
Hilker, M., Kuntschner, H.
Abstract:
The ESO-Garching Scientific Visitor Programme invites astronomers and researchers from around the world to visit ESO in Garching for collaborative scientific activities. Open to scientists actively engaged in research, the programme promotes scientific interaction, innovation, and ESO’s role as a hub of astronomical excellence. Visitors receive logistical and financial support, engage in ESO’s vibrant scientific life, and contribute to its projects. Applications are reviewed by the Scientific Visitor Selection Committee. This programme aligns with ESO’s mission to foster international collaboration in astronomy and its vision to work with and for the astronomy community.

Page 37-38 (PDF)
Nazari, P., Jerabkova, T. et al.
Usage of Artificial Intelligence by ESO Telescope Users
More...
ADS BibCode: 2025Msngr.194...39N
Authors:
Nazari, P., Jerabkova, T., Patat, F.
Abstract:
With the increasing integration of artificial intelligence (AI) and large language models (LLMs) into various fields, it is crucial to understand their capabilities and usage within the scientific community. This study explores the adoption and impact of these technologies among astronomers using ESO telescopes, specifically in the context of proposal preparation and review. We shared a survey with the ESO telescope users to investigate this further. We received 827 responses and found that around 20–30% of the participants use LLMs when preparing proposals and about 3% of the participants use them when reviewing proposals. We also found that there is a divide in how the usage of AI is perceived when proposals are prepared/reviewed, pointing to the need for ESO to establish clearer guidelines. These guidelines will be released for the next period.

Page 39-40 (PDF)
De Breuck, C., Díaz Trigo, M.
Report on the ESO workshop "The Promises and Challenges of the ALMA Wideband Sensitivity Upgrade"
More...
ADS BibCode: 2025Msngr.194...41B
Authors:
De Breuck, C., Díaz Trigo, M.
Abstract:
The Atacama Large Millimeter/submillimeter Array (ALMA) is undergoing the most ambitious project since its inauguration: the Wideband Sensitivity Upgrade (WSU). The WSU will increase the instantaneous bandwidth by as much as a factor of four while retaining full spectral resolution over the entire bandwidth, thus resulting in increases of the spectral scan speed of up to a factor of 50 for the highest spectral resolution. In addition, an upgrade of the full signal chain of ALMA — from the receivers and digitisers all the way through to the correlated data — will result in increases in sensitivity for all observations. However, the increased bandwidth and throughput bring several technical challenges. In June 2024, we organised the first conference at ESO in Garching to inform the ALMA community about all the details of this upgrade. Here we report on the outcome of this meeting.

Page 41-43 (PDF)
Jerabkova, T., Concas, A. et al.
Report on the ESO workshop "Galaxies at Crossroads: Outflows and IMF in the VLT/ELT/ALMA/JWST Era"
More...
ADS BibCode: 2025Msngr.194...44J
Authors:
Jerabkova, T., Concas, A., Langan, I., Alcalde Pampliega, B., van de Ven, G., Matthee, J.
Abstract:
The international workshop Galaxies at Crossroads gathered a diverse group of researchers to address pivotal themes in galaxy evolution, including galactic outflows, the stellar initial mass function, and the mass-metallicity relation. Hosted in collaboration with Masaryk University, the event featured a robust scientific programme complemented by interactive activities, emphasising collaboration and fostering early-career participation. The location in Brno, close to the University of Vienna and the Institute of Science and Technology Austria, provided an ideal and sustainable meeting point in central Europe, easily accessible by train. This report highlights the science, the participant statistics, and how effective it can be when workshops are organised outside of ESO to foster stronger interactions between the community and ESO.

Page 44-46 (PDF)
Miotello, A., Macias, E.
Report on the ESO workshop "New Heights In Planet Formation"
More...
ADS BibCode: 2025Msngr.194...47M
Authors:
Miotello, A., Macias, E.
Abstract:
Planet formation is a widespread by-product of the process of star formation itself and occurs within protostellar discs made of gas and dust that orbit the new-born star. In the past few years new observations of discs at various wavelengths — thanks to new-generation facilities — have revolutionised the field of planet formation and challenged some of the traditional theories. This workshop brought together around 200 scientists from all over the World to review the state of the art, pinpoint the main open questions, and explore new avenues. As well as invited reviews and talks, and contributed talks, the scientific programme offered ample space for informal poster viewing sessions.

Page 47-48 (PDF)
Emsellem, E., Vernet, J. et al.
Report on the ESO workshop "A Decade of Discoveries with MUSE and Beyond"
More...
ADS BibCode: 2025Msngr.194...49E
Authors:
Emsellem, E., Vernet, J., Hibon, P., Fraser-McKelvie, A., Barnes, A.
Abstract:
The Multi Unit Spectroscopic Explorer (MUSE) spectrograph is currently the most in-demand instrument at the VLT and since its commissioning in 2014 it has served a broad scientific community covering many research fields in astrophysics. As a stable, relatively wide-field, two-dimensional, spectrophotometric facility in the optical, assisted by state-of-the-art adaptive optics, MUSE has revolutionised our perspective on the use of integral-field spectroscopy. This has been accompanied by a steep learning curve in the community on how to best reduce, analyse and exploit its unique datasets. This dedicated workshop was a unique opportunity to review the scientific achievements that MUSE has allowed over the last decade, to better understand and reflect on the synergies between MUSE and other facilities and to discuss the associated present and future challenges it entails. This workshop witnessed the gathering of a strong, diverse and interconnected community that could report on their experience and results and discuss potential avenues for the future, further emphasising the benefit of collaborative developments and shared knowledge.

Page 49-52 (PDF)
De Simone, M., Drevon, J. et al.
Fellows at ESO
More...
ADS BibCode: 2025Msngr.194...53E
Authors:
De Simone, M., Drevon, J., Artur de la Villarmois, E.

Page 53-56 (PDF)

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