ESA’s space telescope captures the astonishing diversity of galaxies – and MPE scientists trace how mergers shape their cores
ESA’s Euclid space telescope is revealing the patterns of galaxy evolution, capturing the shapes, sizes, and structures of millions of galaxies across cosmic time. Scientists from the Max Planck Institute for Extraterrestrial Physics (MPE) are using these data to trace how galaxies grow, merge, and transform, including identifying hundreds of systems with secondary nuclei that hint at the formation channels of supermassive black hole binaries. Euclid also uncovers rare systems with highly ionized emission lines and thousands of previously hidden dwarf galaxies, providing key insights into the building blocks of larger systems like the Milky Way. Together, these observations offer a comprehensive view of how galaxies and their central black holes coevolve across the universe.
ESA’s Euclid space telescope is revealing the patterns of galaxy evolution, capturing the shapes, sizes, and structures of millions of galaxies across cosmic time. Scientists from the Max Planck Institute for Extraterrestrial Physics (MPE) are using these data to trace how galaxies grow, merge, and transform, including identifying hundreds of systems with secondary nuclei that hint at the formation channels of supermassive black hole binaries. Euclid also uncovers rare systems with highly ionized emission lines and thousands of previously hidden dwarf galaxies, providing key insights into the building blocks of larger systems like the Milky Way. Together, these observations offer a comprehensive view of how galaxies and their central black holes coevolve across the universe.
Summary:
Euclid Telescope: ESA's Euclid space telescope captures diverse galaxy forms and structures, enhancing understanding of galaxy evolution and mergers.
Galaxy Evolution: Researchers from the Max Planck Institute for Extraterrestrial Physics (MPE) study how galaxies grow and merge, identifying systems with secondary nuclei that may host supermassive black hole binaries.
Data Insights: The first data release includes millions of galaxies, allowing astronomers to investigate connections between galaxy morphology and environmental influences.
Research Breakthroughs: Euclid’s sharp, wide-field images enable the systematic study of the central structures of galaxies and the identification of rare phenomena—including highly ionized emission lines and previously hidden dwarf galaxies—providing crucial insights into galaxy formation.
Comprehensive View: The findings illustrate the relationship between galaxy structure, star formation history, and cosmic environment, offering a holistic view of galactic evolution.
After just one year of observations, ESA’s space telescope Euclid is shedding new light on one of astronomy’s oldest questions: why does the universe contain such a stunning variety of galaxies? Just like flowers, galaxies come in a large variety of different colours, sizes, and shapes — all encapsulated in the term: morphology.
Are these different morphologies linked? How is the evolution of blue spiral galaxies related to that of giant elliptical galaxies? And how much does a galaxy’s environment — whether it lives in crowded clusters or cosmic solitude — influence its shape and fate? With millions of galaxies now catalogued in Euclid’s first data release (Q1, March 2025, ESA), astronomers are gaining access to a new treasure trove of data to address these questions.
Euclid’s sharp, wide-field view marks a breakthrough in extragalactic astronomy. Its images combine exceptional depth and resolution, allowing scientists to study more than 1.2 million large galaxies in its first year alone—and tens of millions over its six-year mission.
We understand today that the diversity of galaxies — from majestic grand-design spirals like our own Milky Way to giant ellipticals such as the mighty Messier 87 — is a consequence of their evolutionary paths. Galaxies begin their lives on the right side of the Hubble diagram (see Figure above) as disky, blue, star-forming systems. They move to the left in the diagram as they grow, gradually exhaust their gas supplies, and merge with other systems, eventually forming large elliptical galaxies.
Galaxy Evolution: Researchers from the Max Planck Institute for Extraterrestrial Physics (MPE) study how galaxies grow and merge, identifying systems with secondary nuclei that may host supermassive black hole binaries.
Data Insights: The first data release includes millions of galaxies, allowing astronomers to investigate connections between galaxy morphology and environmental influences.
Research Breakthroughs: Euclid’s sharp, wide-field images enable the systematic study of the central structures of galaxies and the identification of rare phenomena—including highly ionized emission lines and previously hidden dwarf galaxies—providing crucial insights into galaxy formation.
Comprehensive View: The findings illustrate the relationship between galaxy structure, star formation history, and cosmic environment, offering a holistic view of galactic evolution.
After just one year of observations, ESA’s space telescope Euclid is shedding new light on one of astronomy’s oldest questions: why does the universe contain such a stunning variety of galaxies? Just like flowers, galaxies come in a large variety of different colours, sizes, and shapes — all encapsulated in the term: morphology.
Are these different morphologies linked? How is the evolution of blue spiral galaxies related to that of giant elliptical galaxies? And how much does a galaxy’s environment — whether it lives in crowded clusters or cosmic solitude — influence its shape and fate? With millions of galaxies now catalogued in Euclid’s first data release (Q1, March 2025, ESA), astronomers are gaining access to a new treasure trove of data to address these questions.
Euclid’s sharp, wide-field view marks a breakthrough in extragalactic astronomy. Its images combine exceptional depth and resolution, allowing scientists to study more than 1.2 million large galaxies in its first year alone—and tens of millions over its six-year mission.
We understand today that the diversity of galaxies — from majestic grand-design spirals like our own Milky Way to giant ellipticals such as the mighty Messier 87 — is a consequence of their evolutionary paths. Galaxies begin their lives on the right side of the Hubble diagram (see Figure above) as disky, blue, star-forming systems. They move to the left in the diagram as they grow, gradually exhaust their gas supplies, and merge with other systems, eventually forming large elliptical galaxies.
A comprehensive view of cosmic evolution
Euclid’s Q1 release covers 63 square degrees of the extragalactic sky — only about 0.5% of the total dataset the mission will ultimately deliver. Yet, even this small fraction already enables a remarkable range of high-impact studies across all areas of extragalactic astronomy, demonstrating one of Euclid’s key strengths: its ability to efficiently survey vast regions of the sky and reveal rare astronomical phenomena.
Another example is the study by Daniela Vergani et al., co-led by Christoph Saulder (MPE), which identifies a rare population of 65 galaxies exhibiting highly ionised emission lines — signatures of extreme astrophysical phenomena such as active galactic nuclei, shock fronts, or Wolf–Rayet stars — offering a new window into the energetic feedback mechanisms shaping galaxy evolution.
With its remarkable sensitivity, Euclid also reveals that the most common galaxies in the Universe are not the majestic spirals but tiny dwarf galaxies—faint, low–surface-brightness systems that were once too elusive to study in detail. Among the 2,674 dwarf galaxies identified so far, about 58% are dwarf ellipticals and 42% are dwarf irregulars, some containing compact blue cores or globular clusters. These dwarfs are thought to be the building blocks of larger systems like our own Milky Way, offering vital clues to cosmic assembly on the smallest scales.
These studies — from tiny dwarfs to giant ellipticals — demonstrate Euclid’s extraordinary ability to provide a complete, multi-scale view of galaxy formation and evolution. Its data reveal the physical links between a galaxy’s structure, its star-formation history, and its cosmic environment, connecting all phases of galactic life into a single, coherent picture. Euclid is transforming our understanding of the Universe’s “tuning fork,” showing how galaxies light up with star formation, collide, and fade — and how, at their hearts, black holes and stellar cores evolve together.
Another example is the study by Daniela Vergani et al., co-led by Christoph Saulder (MPE), which identifies a rare population of 65 galaxies exhibiting highly ionised emission lines — signatures of extreme astrophysical phenomena such as active galactic nuclei, shock fronts, or Wolf–Rayet stars — offering a new window into the energetic feedback mechanisms shaping galaxy evolution.
With its remarkable sensitivity, Euclid also reveals that the most common galaxies in the Universe are not the majestic spirals but tiny dwarf galaxies—faint, low–surface-brightness systems that were once too elusive to study in detail. Among the 2,674 dwarf galaxies identified so far, about 58% are dwarf ellipticals and 42% are dwarf irregulars, some containing compact blue cores or globular clusters. These dwarfs are thought to be the building blocks of larger systems like our own Milky Way, offering vital clues to cosmic assembly on the smallest scales.
These studies — from tiny dwarfs to giant ellipticals — demonstrate Euclid’s extraordinary ability to provide a complete, multi-scale view of galaxy formation and evolution. Its data reveal the physical links between a galaxy’s structure, its star-formation history, and its cosmic environment, connecting all phases of galactic life into a single, coherent picture. Euclid is transforming our understanding of the Universe’s “tuning fork,” showing how galaxies light up with star formation, collide, and fade — and how, at their hearts, black holes and stellar cores evolve together.
Contacts:
Dr. Maximilian Fabricius
Leader German Science Data Center SDC-DE
Tel: +49 89 30000-3712
Fax: +49 89 30000-3569
mxhf@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics
Prof. Dr. Roberto Saglia
Scientist OPINAS
Tel: +49 89 30000-3495
saglia@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics
Dr. Christoph Saulder
Postdoc OPINAS
Tel: +49 89 30000-3774
csaulder@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics
Further Information
Euclid opens a treasure trove of data: MPE plays a crucial role in exploring the dark universe
March 19, 2025
The first Euclid data published by ESA (Q1) provide impressive
insights into the depths of the universe. They include high-resolution
images of 26 million galaxies, reveal the finest structures and make it
possible for the first time to precisely determine the shape and
distance of more than 380,000 galaxies. This data is a milestone and yet
only marks the beginning of research into dark matter and dark energy.
And the Max Planck Institute for Extraterrestrial Physics (MPE) plays a
central role in all of this.
more
Zoom into the first page of Euclid’s great cosmic atlas
October 15, 2024
Euclid reveals the first deep view into the cosmos, spanning an area of 500 full moons in the sky.
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MPE-built optical assembly fully integrated on EUCLID-NISP
December 21, 2018
Last week at LAM Marseille, the optical assembly consisting of the camera lens assembly “CaLA” and the corrector lens assembly “CoLA” have been fully integrated on the near-infrared optics NISP for the Euclid satellite. Euclid is an ESA mission, planned to launch in 2022 to study the “Dark Universe”. Scientists at the Max Planck Institute for Extraterrestrial Physics are responsible for the overall optical design of the near-infrared instrument NISP NI-OA.
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