Date: November 19, 2025
The European Space Agency’s (ESA) Euclid space telescope has just delivered a staggering report card after its first year of routine science operations. While the telescope has detected hundreds of millions of sources, a new detailed analysis of 1.2 million complex galaxies has allowed astronomers to update one of the most famous diagrams in astronomy: the "Galactic Tuning Fork."
This finding is not just a catalogue; it is a moving history of the universe, showing us exactly how galaxies grow, merge, and die.
The Headline Figure: Why 1.2 Million?
Euclid launched in July 2023 with the goal of creating the largest, most accurate 3D map of the Universe. By November 2025, after roughly one year of full scientific operations, it has captured vast swathes of the sky.
While the telescope’s wide surveys have spotted over 100 million objects (including stars and faint blips), the figure of 1.2 million refers to the specific set of large, high-quality galaxy images that are detailed enough to reveal their internal structure, shape, and history.
The Distinction: Identifying a spot of light is easy. resolving its spiral arms, central bar, and collision history from billions of light-years away is the "Euclid difference."
1. The "Galactic Tuning Fork" 2.0
For nearly a century, astronomers have used the "Hubble Tuning Fork" to classify galaxies—splitting them into spirals (like our Milky Way) and ellipticals (fuzzy blobs). For a long time, this was just a classification system, like sorting leaves by shape.
Euclid’s data has turned this static picture into a movie. By analyzing these 1.2 million galaxies, researchers at the Max Planck Institute for Extraterrestrial Physics (MPE) have confirmed the evolutionary path of the cosmos:
The Beginning (The Prongs): Galaxies start as blue, star-forming discs. They are vibrant, churning out new suns, and rotating quickly.
The Transition (The Handle): As they age, they burn through their gas or collide with neighbors.
The End: They transform into massive, red, featureless "elliptical" galaxies. These are the "dead" remnants of cosmic collisions, where star formation has mostly ceased.
Euclid allows us to see the "in-between" stages—the messy, violent mergers that bridge the gap between a lively spiral and a quiet elliptical.
2. Black Hole Mergers: The "Secondary Nuclei"
One of the most exciting finds from this dataset is the identification of secondary nuclei.
When two galaxies crash into each other, their supermassive black holes (which sit at the center of each) eventually sink to the middle of the new, larger galaxy. Euclid’s sharp vision has spotted hundreds of galaxies that appear to have two hearts—evidence that a merger is currently happening.
Why it matters: These "dual core" galaxies are the precursors to the emission of gravitational waves. Studying them helps us understand how supermassive black holes grow to weigh billions of times the mass of our Sun.
3. The "Building Blocks": Dwarf Galaxies
While the massive spirals get the glory, Euclid has also shone a light on the underdogs: dwarf galaxies.
In just this early dataset, Euclid identified 2,674 dwarf galaxies that were previously too faint to be studied in detail.
58% are dwarf ellipticals (miniature dead galaxies).
42% are dwarf irregulars (messy, small blobs).
These tiny galaxies are thought to be the "building blocks" of the universe. Larger galaxies like the Milky Way likely grew by eating these smaller dwarfs over billions of years. Euclid is finally letting us see the "crumbs" left over from this cosmic feast.
4. The "Galactic Cirrus"
Euclid’s visible-light camera (VIS) is so sensitive that it picked up something in our own neighborhood while looking out at the deep universe.
The images are filled with wispy, light-blue clouds known as "Galactic Cirrus." These are clouds of gas and dust hanging between the stars of our own Milky Way. They reflect the light of the galaxy like fog reflecting a streetlamp. While they are a nuisance for cosmologists trying to see through them, for astrophysicists, they are a beautiful, high-resolution map of the interstellar medium in our own backyard.
Summary: What We Have Learned So Far
| Feature | Discovery | Significance |
| Morphology | 1.2 million detailed galaxy shapes | Confirms galaxies evolve from blue spirals to red ellipticals via mergers. |
| Black Holes | Secondary nuclei identified | Shows how supermassive black holes merge and grow. |
| Dwarf Galaxies | ~2,700 new dwarfs found | reveals the primitive "building blocks" of large galaxies. |
| Dark Universe | 1% of sky mapped (so far) | The 3D map of Dark Matter is successfully being built, pixel by pixel. |
What’s Next?
This 1.2 million figure comes from just the start of the mission and early data releases (including the massive 208-gigapixel mosaic released in late 2024). Over its 6-year lifespan, Euclid will observe billions of galaxies and create a 3D map covering more than one-third of the entire sky.
If the first year was the "opening paragraph," Euclid is now writing the rest of the history of the universe.