Euclid's 6-gigapixel glimpse into the centre of our galaxy

Hidden among these millions of stars are planets we cannot yet see, and a very special one that we call home. This may look like a distant galaxy, but it's actually our own, the Milky Way galaxy. We can't photograph our galaxy from the outside. Instead, this is a map created from years of observations by the Gaia Space Telescope, transforming billions of measurements into a map of the home we inhabit. We are here, tucked between the Milky Way's spiral arms in a relatively calm corner of the galaxy, where the conditions were just right for life to emerge. As we move towards the bright, crowded centre of our galaxy, we begin to see reality itself. This is the Galactic Bulge. It is here that ESA's Euclid Space Telescope has captured the largest and most detailed visible light photo ever made of our galaxy's centre. Euclid was built to study dark matter and dark energy by looking deep into the distant Universe, but this time it turned its gaze inward. In just about 26 hours, it captured a vast mosaic containing tens of millions of stars. And it is this extreme density that makes the image so valuable, because in such crowded fields, something remarkable becomes possible. A phenomenon called microlensing. Microlensing happens when the gravity of a star, or a planet orbiting it, briefly bends and magnifies the light of another star behind it, acting like a natural cosmic lens. In a field this crowded, stars are constantly drifting past one another in our line of sight. And in rare occasions, just for a moment, one object passes perfectly in front of another. The background star brightens, then fades again. That flash can reveal the presence of an otherwise invisible planet, and even allow astronomers to calculate its mass. What we're looking at could be thousands of planets hidden in plain sight, but planets do not exist in isolation. Every hidden world belongs to a larger story, one that begins long before the planet itself. Before planets can form, there must be stars. Before that, there must be clouds of gas and dust, the raw material from which entire solar systems are born. Within this single field of view, Euclid is not only helping to reveal planets hidden among the stars, it is revealing the cycle that creates them. A timeline spanning millions of years. A story of birth, transformation and renewal. What may seem like an empty space is anything but. This is an obscuring nebula, a vast molecular cloud made of hydrogen gas, dust and the raw material from which stars are born. Dense clouds of gas and microscopic particles drift between us and the bright galactic bulge behind them, blocking the starlight beyond, much like storm clouds obscuring the Sun on Earth. Hidden inside such clouds are the ingredients for future solar systems. Over millions of years, gravity slowly pulls this material inward. The cloud begins to fragment into smaller clumps that further contract under their own weight, growing denser, hotter until they ignite. Somewhere inside this dark region, new stars and planets are being formed. Stars are born from clouds like this. They shine for millions or billions of years. When they die, they shed newly forged elements back into space, enriching the galaxy with the material that will go to form the next generation of stars, planets and possibly life. In this other view, we see a glow among the stars. Suspended among millions of stars is a cloud of hydrogen gas, shining with a deep crimson light. Within the crowd of the Milky Way star, a new generation of stellar giants has awakened. These young stars are immense, tens of times more massive than our Sun, and they shine with extraordinary intensity. Their light floods the surrounding cloud with powerful ultraviolet radiation, energising the hydrogen around them. The atoms absorb that energy, become excited and for a brief moment exist in a heightened state. As the hydrogen settles back into equilibrium, it releases the excess energy as light, and so the cloud begins to shine. Across the darkness, billions of atoms repeat this process over and over again, creating the soft red glow now visible to Euclid. What we're seeing is the aftermath of a stellar birth, a cosmic nursery illuminated by the very stars it has just created. And here, what remains is a young star cluster, a family of stars and planets born together from the same collapsing cloud of gas. Stars are rarely born alone. These stars are siblings, sharing a common birthplace and history. When a giant molecular cloud collapses, it fragments into hundreds or even thousands of stars forming at once. Roughly 8,700 light years away, this cluster is still travelling through the galaxy as a group, carrying the imprint of its origin. The cloud that once surrounded it is gone, swept away over millions of years by stellar radiation and winds. What stands out are the bluish stars scattered among the gold, like the blue core of a flame, they are the hottest stars in the Universe. They burn intensely and live fast. The golden and yellow stars around them are cooler, calmer and far longer lived, like our own Sun. The blue stars are cosmic sprinters. Most will end in supernovae, seeding the galaxy with new elements. The smaller stars will endure, but even this cluster will not last forever. Over time it will slowly dissolve, its stars drifting apart under the Milky Way's gravity. And now we arrive to the golden heart of our Milky Way, a vast concentration of ancient stars packed into the centre of our galaxy. This is a region where star formation has mostly come to an end. The gas has been consumed, recycled and redistributed across the galaxy. What we see now is the accumulation of billions of stars layered over billions of years. In this dense field, something rare and extraordinary becomes possible because of microlensing. When a star briefly brightens, astronomers can calculate the mass of the object which is passing in front of it. Sometimes another star, sometimes a planet orbiting that star and sometimes a planet with no star at all. These rogue worlds drift freely through the Milky Way, invisible except for the brief time their gravity bends the light of a distant star. Which means this single image is not static, it is a map of future events, thousands of brief brightenings waiting to happen across time. Each one is a potential discovery. We have already discovered more than 6,000 exoplanets beyond our Solar System. Euclid is expected to identify more than 100,000 transiting planets, each leaving a tiny signature in the light of its star. No one has ever captured the Milky Way's galactic bulge like this before. This is the first visible light image to combine such depth, resolution and sky coverage, creating an unprecedented portrait of the crowded heart of our galaxy. It is a reference that astronomers will return to for years to come. This is the beginning of a new era of exploration, a map revealing what has always been there, hidden in the fabric of the galaxy. And from this crowded, glowing heart of the Milky Way, the galaxy stretches outwards once more, into its spiral embrace, into stellar nurseries, into obscuring clouds and glowing nebulae, back to one small yellow star in one quiet corner of the galaxy where a small blue planet gave rise to beings who now search for worlds beyond their own.