Euclid is on a quest to unravel one of the universe’s greatest mysteries: why it’s expanding faster and faster. With help from NASA, this space telescope is capturing sweeping views of billions of galaxies, allowing scientists to peer into the deep past.
Using light that took billions of years to reach us, researchers are building 3D maps of the cosmos to track the strange force known as dark energy. Along the way, they’re mapping invisible dark matter through gravitational lensing, hoping to uncover how these cosmic ingredients have shaped everything from galaxies to the universe’s fate.
Mission to Uncover Cosmic Acceleration
The Euclid mission, led by the European Space Agency (ESA) with support from NASA, is designed to investigate one of the universe’s biggest mysteries: why the expansion of the universe is speeding up. Scientists refer to the unknown force behind this acceleration as dark energy, and Euclid’s goal is to better understand it by capturing images of billions of galaxies across space and time.
On March 19, ESA released a preview of early mission data to the public. This initial release, described as a “quick look,” focuses on selected regions of the sky. It offers a first glimpse of what Euclid can do and helps researchers fine-tune their tools and techniques for analyzing the much larger datasets still to come.
Billions of Galaxies, Billions of Light-Years
The newly shared data includes observations of Euclid’s three “deep fields”—areas of the sky where the telescope will make its most far-reaching observations. The preview covers just one week of viewing time but already includes 26 million galaxies, some more than 10.5 billion light-years away.
Euclid, which launched in July 2023, is expected to observe over 1.5 billion galaxies during its six-year prime mission. By the end of that mission, it will have spent roughly 40 weeks observing the deep fields, collecting more and more light over time—similar to leaving a camera shutter open longer to capture a clearer image in low light. This will allow scientists to see fainter, more distant galaxies than ever before.
Not Just More Galaxies — More Insight
The first deep field observations, taken by NASA’s Hubble Space Telescope in 1995, famously revealed the existence of many more galaxies in the universe than expected. Euclid’s ultimate goal is not to discover new galaxies but to use observations of them to investigate how dark energy’s influence has changed over the course of the universe’s history.
In particular, scientists want to know how much the rate of expansion has increased or slowed down over time. Whatever the answer, that information would provide new clues about the fundamental nature of this phenomenon. NASA’s Nancy Grace Roman Space Telescope, set to launch by 2027, will also observe large sections of the sky in order to study dark energy, complementing Euclid’s observations.
3D Maps of the Universe’s Past
To study dark energy’s effect throughout cosmic history, astronomers will use Euclid to create detailed, 3D maps of all the stuff in the universe. With those maps, they want to measure how quickly dark energy is causing galaxies and big clumps of matter to move away from one another. They also want to measure that rate of expansion at different points in the past. This is possible because light from distant objects takes time to travel across space. When astronomers look at distant galaxies, they see what those objects looked like in the past.
For example, an object 100 light-years away looks the way it did 100 years ago. It’s like receiving a letter that took 100 years to be delivered and thus contains information from when it was written. By creating a map of objects at a range of distances, scientists can see how the universe has changed over time, including how dark energy’s influence may have varied.
But stars, galaxies, and all the “normal” matter that emits and reflects light is only about one-fifth of all the matter in the universe. The rest is called “dark matter” — a material that neither emits nor reflects light. To measure dark energy’s influence on the universe, astronomers need to include dark matter in their maps.
How Gravity Reveals the Invisible
Although dark matter is invisible, its influence can be measured through something called gravitational lensing. The mass of both normal and dark matter creates curves in space, and light traveling toward Earth bends or warps as it encounters those curves. In fact, the light from a distant galaxy can bend so much that it forms an arc, a full circle (called an Einstein ring), or even multiple images of the same galaxy, almost as though the light has passed through a glass lens.
In most cases, gravitational lensing warps the apparent shape of a galaxy so subtly that researchers need special tools and computer software to see it. Spotting those subtle changes across billions of galaxies enables scientists to do two things: create a detailed map of the presence of dark matter and observe how dark energy influenced it over cosmic history.
Shaping the Sky, Pixel by Pixel
It is only with a very large sample of galaxies that researchers can be confident they are seeing the effects of dark matter. The newly released Euclid data covers 63 square degrees of the sky, an area equivalent to an array of 300 full Moons. To date, Euclid has observed about 2,000 square degrees, which is approximately 14% of its total survey area of 14,000 square degrees. By the end of its mission, Euclid will have observed a third of the entire sky.
The dataset released this month is described in several preprint papers. The mission’s first cosmology data will be released in October 2026. Data accumulated over additional, multiple passes of the deep field locations will also be included in the 2026 release.
Explore Further: Just 0.4% In, Euclid’s Dark Universe Map Already Reveals 26 Million Galaxies
More About Euclid
Euclid is a European Space Agency (ESA) mission designed to explore the mysteries of dark energy and dark matter by mapping the geometry and large-scale structure of the universe. Launched as part of ESA’s Cosmic Vision Programme, Euclid is a medium-class mission built to answer one of cosmology’s most profound questions: why is the universe expanding at an accelerating rate?
The mission is led and operated by ESA, with major contributions from NASA and other international partners. The scientific heart of the mission lies with the Euclid Consortium, a collaboration of more than 2,000 scientists from over 300 institutes across 15 European countries, the United States, Canada, and Japan. The Consortium is responsible for providing the mission’s scientific instruments and for analyzing the data Euclid collects.
Thales Alenia Space was selected by ESA as the prime contractor for the satellite and service module, while Airbus Defence and Space developed the payload module, which includes Euclid’s space telescope.
NASA supports the mission through three dedicated science teams. NASA’s Jet Propulsion Laboratory (JPL) played a critical role in the development of Euclid’s Near Infrared Spectrometer and Photometer (NISP), specifically by designing and building the sensor-chip electronics and managing the procurement and delivery of NISP detectors. These components were rigorously tested at NASA’s Detector Characterization Lab at Goddard Space Flight Center in Greenbelt, Maryland.
The Euclid NASA Science Center at IPAC (ENSCI), located at Caltech in Pasadena, California, coordinates U.S.-based scientific participation and facilitates access to mission data. All U.S. science data are archived at NASA’s Infrared Science Archive (IRSA), also hosted at IPAC. JPL, which contributed significantly to the mission’s hardware and technical expertise, is managed by Caltech for NASA.
With its international collaboration, advanced instrumentation, and cosmic-scale mission goals, Euclid is poised to transform our understanding of the invisible forces shaping the universe.
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1 Comment
Interesting, but of course it hardly means a thing if you can’t go there yourself, in person and not have to spend an entire afternoon getting there; just as a flight or fancy; what if all those galaxies could be reduced to imperfections in a holographic time crystal? Impossible and senseless for sure; just like the senseless time crystals that we already have that don’t correspond to any other sort of reality outside of itself; so why not reimagine ourselves as being inside a time crystal? We’ll never get anywhere meaningful if we attempt to travel solely via space.