Euclid Studied Our Galactic Centre. This Is What It Found.

This is the most detailed visible light photograph we've ever taken of our Milky Way's core. Captured by the European Space Agency's Euclid Telescope, this picture contains more than 60 million stars. But that's not all that's buried within this spectacular image. Deep in that swarm of starlight are planets, and lots of them. Some are big and hot. Some Some are frozen, cold worlds, and some exist outside of planetary systems altogether, orbiting nothing at all. All we have to do now is find them. I'm Alex McColgan and you're watching Astrum. Join me as we reveal the wonders hiding within this stunning image. We'll delve into what it takes to find elusive exoplanets and explore how Euclid, a telescope designed to be a dark universe detective has come to play a part in this mission. Euclid wasn't built to be a planet hunter. In fact, it wasn't even made to look inside the Milky Way. Launched in 2023, this European Space Agency telescope was made to stare into deep, dark parts of the night sky to explore the composition and evolution of the universe across space and time, far from the blinding concentration of stars clustered around our own galactic centre. Orbiting at Lagrange Point 2, a gravitational equilibrium and average distance of 1.5 million kilometres from Earth, Euclid keeps Earth, the Moon and the Sun at its back. Within just one week of starting observations back in 2024, it had already charted and imaged some 26 million galaxies. Since then, Euclid has witnessed gamma-ray bursts and ancient quasars, found hundreds of strong gravitational lens candidates, and uncovered an extremely rare Einstein ring. There are hopes that one day it will be able to explain the very nature of dark energy and dark matter, and with a six year long initial mission, Euclid is staring out into the dark right now. However, after nearly two years of normal operations, this telescope was tasked with a special assignment. For one day only, on the 23rd of March 2025, Euclid turned around and pointed its camera inward towards the bright, crowded heart of the Milky Way, a region that is notoriously difficult to image, given our solar system sits within the Milky Way's disk. Our view from here means we have to look through thick clouds of interstellar dust and gas that block visible light to even catch a glimpse of the cluttered, star-filled bulge at its centre. In fact, the space this photo looks through is so crowded that from our position out on a spiral arm, we're essentially spying through a tiny, unobstructed keyhole to see the heart of our galaxy, packed with stars and other objects. you only have to zoom in from the wide view of this image to see what i mean it took about 26 hours and a mosaic of nine different shots called pointings for euclid to create this special image of our galaxy center i hope you'll agree with me that it's absolutely spectacular to look at but what i find really interesting is how much better it is than the glimpses we have from other the telescopes. Historically, we've only had luck viewing this region in such detail in radio and infrared wavelengths. So what makes Euclid able to use visible light? Well, because of its initial mission goal, you'd think Euclid would be badly suited for capturing crowded star fields. But Euclid's exceptionally sharp optics and wide area capabilities make it surprisingly versatile. Not only is it a great choice for studying the deep cosmos, And it also happens to be very well suited to capturing crowded star fields, just like those within our own galactic bulge. Its 600 megapixel camera is fast, wide, and sharp enough to pick out individual stars even in the most crowded parts of the sky. Each of Euclid's nine pointings captured an area 270 times larger than Hubble's entire field of view, while still matching its sharpness. Keck Observatory would need about 2000 hours to observe the same area that Euclid did in just over a day. In other words, I really can't overstate what a technological marvel it is. Euclid is unmatched in almost every way. And the result is the highest resolution photograph ever taken of the galactic bulge in visible light. It covers 4.8 square degrees of sky, or roughly 22 times the area of the full moon as seen from Earth. That's massive. Of course, merely taking a photo this large is only half the challenge. The real work comes afterwards, finding the patterns, spotting the outliers, and turning vast amounts of information into meaningful discoveries. Whether you're studying galaxies, running experiments, improving manufacturing processes, or exploring complex systems of any kind, the challenge is often the same. How do you organize and make sense of all that data. That's where the sponsor of today's video, Jump Statistical Discovery, comes in. Whether you're a scientist, engineer, student, or simply curious about the cosmos, Jump helps you analyze complex data through an intuitive point-and-click interface. You can quickly visualize information, uncover relationships, build predictive models, and communicate insights. It comes ready to use, saving you hours of coding, but works alongside tools like Python if coding is up your alley. From experimental results and sensor readings to quality metrics and research data, Jump is designed to help you move from raw information to confident decisions faster. Scan my QR code or click the link in the description below to head over to the Jump website to find out more, and even download a free trial to see what discoveries you can make first-hand. As scientists began to examine it, it became obvious that the Euclid data was packed with discoveries. So here's what we found so far. This photo contains more than 60 million stars. If we zoom out and put that number into perspective, the region being photographed represents just one part of the Milky Way's enormous central bulge. In total, it contains roughly 10 billion stars. This means that Euclid is giving us an extraordinarily detailed glimpse, most detailed yet, but it's still only a small portion of the gigantic stellar population within the central region, just 0.6% of the total stars in this area to be precise. Looking back at the photo, what you can see here is a crowded view of some of the oldest and most densely packed regions of our galaxy. Here the stars glow with a golden hue, because most of them are fairly old and cool. The average age is 8 billion years, although some of the most ancient ones could have been born as many as 13 billion years ago. And while astronomers haven't announced the official identification of any previously unknown stars yet, it's inevitable that this image will, in time, lead to the discovery of stars and other objects that had previously not been catalogued. I personally find the sheer number of identifiable stars in this region absolutely breathtaking. I could spend all day just zooming in and moving the image around. It kind of makes me wish we could look up into the night sky and see something like this with our own eyes. Anyway, it wasn't just stars we can see. Scattered across the image, we can spot things like molecular clouds and nebulae, and even entire star clusters. Just here, zoomed in 10 times from the original, you can see a dark cloud-shaped area. This is LDN 10, a dense molecular cloud in the foreground which obscures the light from the galactic bulge behind and makes it more difficult to map stars in the region. The dust in this molecular cloud absorbs and scatters visible light, producing the dramatic dark band against the bulge's yellow-gold background. There are still stars present behind the cloud, we just can't see them clearly. Looking at another part of the image, we can see one of countless star clusters in the photo. This one is called NGC 6451. Located 8,700 light years away from us, the star cluster appears towards the centre of the image. Here the stars appear brighter and more tightly clustered, with younger bluish white stars that stand out against the yellow warm glow of the dense stellar background. It's thought that the cluster is only 136 million years old, so it really is very young. We can also find nebulae strewn across the image, like this emission nebula. It's made up of the ionized gases sent out from massive stars that recently formed in a spiral arm. Looking through these arms, massive bright blue stars trace areas of new star formation. The ultraviolet light from these regions causes nearby hydrogen to glow red. It's basically like a neon sign powered by stars. But those are just some of the things we can see invisible light. What makes this image even more exciting is what we can't see. Not yet, anyway. In the sea of stars captured by Euclid, other objects are hiding. Countless exoplanets exist in this one image, and not just the ordinary kind. Using various techniques and instruments like the Hubble and Keck telescopes, astronomers have confirmed more than 6,000 of these planets outside our solar system and predict that billions, yes billions, are out there in our galaxy. One way we look for exoplanets is using the transit method, which relies on a planet passing in front of its star as seen from Earth. To do this, astronomers watch to see if a star's light periodically dims ever so slightly, indicating the presence of an exoplanet. Another way uses the radial velocity method, which looks for slight wobbles. When a planet orbits close enough to its star, its gravity causes a tiny change to the star's motion that we can see as subtle changes in the wavelength of its light. A related technique, astrometry, measures that same stellar wobble as tiny changes in the star's position across the sky. And of course, we have also found exoplanets through direct imaging. Here's the problem though. These techniques favour large planets and those close to their stars. They are easier to detect because they produce larger signals. Their transits block more starlight. Their gravity causes a stronger stellar wobble, and their heat makes them brighter, and therefore easier to spot, relative to their host stars. This means that our overall picture of exoplanets in the galaxy is pretty skewed. We found tons of large super-earths that orbit close to their stars, some with surfaces so hot they could vaporise metal. And we found plenty of mini-Neptunes, exoplanets that resemble miniature gas planets. They're too big to be Earth-like, but not quite large enough to be a full-size gas giant. The reason we've found so many of these types of exoplanets is not because these necessarily make up the majority of exoplanets, but because, for the reasons I mentioned above, they're easiest to find. If you'd like to learn more about exoplanets in general, you can find several videos about them on this channel. We even have a playlist dedicated to only our videos on alien worlds. But what about the rest of the exoplanets? What about the ones that hide in the cold dark reaches of their planetary systems? Or in the case of rogue exoplanets, which may not even belong to a planetary system at all. Astronomers expect every star in the Milky Way galaxy to host at least one cold small planet, which makes sense given what we find in our own solar system. But think about what that means in relation to Euclid's image. There are at least 60 million small rocky planets in there, just waiting to be found. And it could be that other types of exoplanets are actually more common than we thought too. There may even be fascinating, entirely new to us types of planets out there, but without a different approach to finding them, we may miss whole populations of worlds. And that's exactly where Euclid comes in. If we want to stand a chance of finding new types of planets, astronomers need a completely different way to identify them. One that doesn't depend on a planet being big, hot or bright. And thankfully, there's one technique that fits the bill. Gravitational microlensing. But it's not the easiest to plan for, as it relies on a chance encounter. The alignment of two stars with an observer. When one star passes in front of the other, it acts like a cosmic-sized magnifying glass. It bends and brightens the light of the further star. The result is like magic. If there's an exoplanet orbiting the nearest star, then its gravity will also bend light in a slightly uneven way. And it's that tiny change in brightness that reveals a hidden planet. Naturally, since this method requires the alignment of stars, then the place in the galaxy with the densest population of stars would offer the most opportunities for stellar alignments. This is why Euclid's gigantic high-definition photo of the galactic centre is so critical. It's full of untapped planet-hunting potential. Microlensing doesn't discriminate based on how far a planet is from its star, or whether it is big or small, hot or cold, or even if it's orbiting a star at all. It is not biased towards finding the easy planets, it can find them all, even rogue ones. This is because microlensing happens when a massive object passes in front of a distant background star, bending and magnifying that star's light with its gravity. The signal comes from the lensing object's mass, not its temperature or size, or whether it even has a host star. A small icy planet floating alone in space bends light exactly the same way a hot Jupiter would given similar mass. Over the past 20 years, almost 300 exoplanets have been found using this method, with ground-based telescopes pointed towards the centre of the Milky Way. And in fact, 51 known planetary systems can be spotted in the image that Euclid took. These include this OGLE, what a name, which is a cold, icy exoplanet that the leader of the team who found it 20 years ago, Jean-Philippe Bulot, describes as a bit like Hoth from Star Wars. Another is this OGLE, which is a unique system, containing two stars and one planet. We'll come back to them a bit later. However, in the case of rogue planets with no host, it won't be two stars lining up that tip off astronomers. In this case, the planet can act as a lens on its own, and each time it passes in front of a background star, the planet's gravity causes a brief increase in brightness. The question is, how many more planets do we think we can find this way? It can take more than 20 days for a telescope to catch a microlensing event, having to wait for the planets to orbit close enough to their star for us to see the light being bent. This means that one photo, from day 1 of observation by Euclid, isn't enough to find new exoplanets, not by itself. I know this is a little disappointing to hear, but instead, this photo will serve as a snapshot in time that astronomers can refer back to as part of a new multi-year, multi-telescope mission. It's a picture of the stars before they overlap in years to come. And because Euclid's image is so detailed, astronomers will be able to clearly see individual stars to measure how fast they move over time. data will allow them to confirm the existence of exoplanets and calculate their mass, something that we haven't been able to do before. But for all of this, we need another new telescope. And thankfully, one is on the way. The Nancy Grace Roman Space Telescope, which launched at the end of August this year, was named after NASA's first chief astronomer and will have a field of view at least 100 times the size of Hubble's. It's anticipated to measure the light from as many as a billion galaxies across its lifetime and the area of the sky Roman telescope is set to observe falls within the image captured by Euclid so even though we can't identify new exoplanets yet Euclid has already captured all future microlensing events that the Roman telescope will detect Roman's Galactic Bulge Time Domain Survey will do what Euclid could not observe this region continuously for years, hunting for brightening and dimming stars that reveal microlensing events. Anyone who observes a microlensing event in this region using the Roman or any other telescope in the future will have to refer back to Euclid data to see how stars looked before they overlapped. So, thanks to Euclid, the hunt can begin immediately once Roman's mission begins in early 2027, and we don't even have to wait until then to start making discoveries. For exoplanets we've already found that fall within Euclid's view, we can use their past observations for a taste of what we will learn once Roman gets involved. Let's go back to those I mentioned earlier. First up is the icy OGLE that lies 20,000 light years away from us. Its star is small and red and has about 20% the mass of our sun, but beyond that we know very little about this alien world, but having this image from Euclid might finally allow astronomers to calculate its precise mass. The same is true for this OGLE. By combining past observations from Keck and Hubble, the new Euclid data will finally allow astronomers to separate the two stars and confirm the planet's mass too. In other words, Euclid is already giving us valuable information about exoplanets, so watch this space for more discoveries coming your way very soon. But, this is not all this spectacular image can be used for, it can also help us investigate other celestial questions. One of the main ones being in relation to brown dwarfs, objects that are too small to sustain the hydrogen fusion that powers a true star. They exist in a kind of gap between giant planets and stars, and these brown dwarfs are exactly the type of faint, easily missed object that a crowded, high resolution image like Euclid's is built to catch. This detail will help astronomers study binary star systems and pin down the individual masses of each star in the system. The stars appear like one in our night sky, but are really two locked in orbit around each other. The binary planetary system with a known exoplanet that I mentioned a moment ago, this ogle, is one example of this. And there are even stranger objects hiding among the 60 million points of light in this photo – isolated black holes. These black holes can't be photographed directly, but they still bend the light of background stars that they happen to drift in front of, producing a microlensing signal just like a planet would, only much stronger. Euclid's wide, high-resolution survey can provide precise measurements of these background objects so that over time we can watch to see if a rogue black hole passes in front and bends their light, and once Roman gets involved, the sky is literally the limit. Together, these telescopes can do science that surpasses what either one was designed to do alone. And all of this is possible because of a single, deliberate detour from Euclid's original surveys. One day, 26 hours, and the stage was set for the discovery of planets that otherwise remained hidden forever. Euclid may not be able to tell us which of the 60 million points of light are hiding these alien worlds, but Roman can. And even though its mission hasn't officially begun done yet, this multi-telescope hunt for exoplanets started the moment Euclid turned around and took that photograph. We don't know exactly what's out there yet. Rogue planets drifting alone, hidden ice worlds, maybe something no one's even thought to look for. But for the first time, we have a way to find them, and I personally can't wait to see what the next few years holds. And what's even better is that we don't have to wait long. The countdown to these exciting discoveries is already running, all thanks to Euclid. Since I started Astrum 12 years ago, things have changed a lot. It's gone from me making all the videos alone, to now where I'm joined by a whole team of people who truly love space as much as I do. But what I'm most proud of is how our community has grown. Right now we're just over 100,000 subscribers away from 3 million, which is something I'd love to hit. Not only because it's a great achievement, but because it's a sign of just how far the wonder of space is spreading. Can you help us get there? Hit like and subscribe now and let's grow Astrum together.