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The powerful Euclid telescope has captured millions of stars and galaxies in a dazzling new mosaic — and it represents just the first piece of a massive puzzle the observatory has been designed to solve.
The European Space Agency mission, launched in July 2023, will create the largest and most accurate 3D map of the cosmos yet to help answer enduring questions about the “dark side” of the universe.
Scientists assembled the first piece of the map, which includes 208 gigapixels, from 260 observations made between March 25 and April 8. But it accounts for a tiny fraction of the broad survey that Euclid will make of the sky in the future, measuring the shape, distance and motion of billions of galaxies.
The mosaic, which includes about 100 million stars and galaxies, made its debut on October 15 at the International Astronautical Congress in Milan, Italy.
“This stunning image is the first piece of a map that in six years will reveal more than one third of the sky. This is just 1% of the map, and yet it is full of a variety of sources that will help scientists discover new ways to describe the Universe,” said Valeria Pettorino, Euclid project scientist at the ESA, in a statement.
One of Euclid’s primary goals is to observe dark matter and dark energy. While dark matter has never been detected, it is believed to make up 85% of the total matter in the universe. Meanwhile, dark energy is a mysterious force thought to play a role in the accelerating expansion of the universe.
Astronomers hope the telescope’s observations of millions of galaxies will reveal hidden forces that provide the universe with its structure and drive its mysterious acceleration rate.
A new perspective of the cosmos
Euclid’s wide perspective can record data from a part of the sky 100 times bigger than what NASA’s James Webb Space Telescope’s camera can capture. But the telescope’s sensitive cameras can also capture intricate details of many celestial objects at once.
For example, the delicate structure of a spiral galaxy in the cluster Abell 3381, located 470 million light-years away, can be seen in the mosaic as well as light blue clouds between the stars in our Milky Way galaxy.
These “galactic cirrus” clouds, so named because they resemble cirrus clouds on Earth, are a mix of gas and dust — and Euclid can capture their faintness with its visible light camera.
Euclid’s first images were released in November 2023, but the telescope began regularly observing the sky in February. So far, the observatory has completed 12% of its survey.
“We have already seen beautiful, high-resolution images of individual objects and groups of objects from Euclid. This new image finally gives us a taste of the enormity of the area of sky Euclid will cover, which will enable us to take detailed measurements of billions of galaxies,” said Jason Rhodes, an observational cosmologist at NASA’s Jet Propulsion Laboratory in Pasadena, California, in a statement. Rhodes is the US science lead for Euclid and principal investigator for NASA’s Euclid dark energy science team.
Seeking evidence of the unseen
In the 1920s, astronomers Georges Lemaître and Edwin Hubble discovered that the universe has been expanding since its birth 13.8 billion years ago. But research that began in the 1990s has shown that something sparked an acceleration of the universe’s expansion about 6 billion years ago, and the cause remains a mystery.
Unlocking the true nature of dark energy and dark matter could help astronomers understand what the universe is made of, how its expansion has changed over time, and whether there is more to understanding gravity than meets the eye. Dark matter and dark energy are also thought to play a role in the distribution and movement of objects, such as galaxies and stars, across the cosmos.
Euclid is designed to observe billions of galaxies that stretch 10 billion light-years away to reveal how matter may have been stretched and pulled apart by dark energy over time. These observations will effectively allow Euclid to see how the universe has evolved over the past 10 billion years.
During its observations, the telescope will catalog 1.5 billion galaxies and the stars within them, collecting a treasure trove of data for astronomers that includes each galaxy’s mass and number of stars created per year.
Euclid’s first images are a promising glimpse of the broader map it will reveal in the future.
“What really strikes me about these new images is the tremendous range in physical scale,” said Mike Seiffert, project scientist at JPL for the NASA contribution to Euclid, in a statement. “The images capture detail from clusters of stars near an individual galaxy to some of the largest structures in the universe. We are beginning to see the first hints of what the full Euclid data will look like when it reaches the completion of the prime survey.”
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