See the First Stunning Test Images From the Euclid Space Telescope

Meant to study the “dark universe,” Europe’s space observatory will eventually peer ten billion years into the past and map more than one-third of the sky

An image of outer space showing distant stars and galaxies in a light red color
A test image taken by Euclid's infrared light instrument showing distant stars and galaxies. ESA / Euclid / Euclid Consortium / NASA, CC BY-SA 3.0 IGO

From more than a million miles away, the European Space Agency’s (ESA) Euclid space telescope has sent its first stunning test images back to Earth.

The pictures, filled with distant galaxies and bright stars, confirm Euclid’s instruments are functioning and provide a small glimpse of the scientific discoveries to come.

Launched on July 1 from Florida’s Cape Canaveral Space Force Station, the telescope will observe billions of galaxies to map how the universe has evolved over time. Astronomers hope this data will shed light on the mysterious dark matter and dark energy that govern the cosmos.

“Although these first test images are not yet usable for scientific purposes, I am pleased that the telescope and the two instruments are now working superbly in space,” Knud Jahnke, an astronomer at the Max Planck Institute for Astronomy in Germany and instrument scientist for the Euclid mission, says in a statement.

“After more than 11 years of designing and developing Euclid, it’s exhilarating and enormously emotional to see these first images,” Giuseppe Racca, Euclid’s project manager at the ESA, says in a statement from the agency. “It’s even more incredible when we think that we see just a few galaxies here, produced with minimum system tuning. The fully calibrated Euclid will ultimately observe billions of galaxies to create the biggest-ever 3D map of the sky.”

Capturing these test views of the cosmos used both of Euclid’s imaging instruments—one that observes in visible light and another that “sees” the longer wavelengths of infrared. Images captured by Euclid’s visible instrument (VIS) will reveal the shapes of galaxies. Those taken with the Near-Infrared Spectrometer and Photometer (NISP) will measure how much light galaxies emit at different wavelengths, which can reveal their distances from Earth, per the ESA statement.

The Euclid spacecraft, about 15 feet tall and 12 feet across, has spent the last several weeks traveling to the second Lagrange point, or L2, located more than 900,000 miles from Earth in the opposite direction from the sun. The James Webb Space Telescope is also in orbit around L2. It’s an ideal place for a space-based observatory, in part because gravitational pulls of the Earth and sun balance out orbital forces, allowing spacecraft to stay in a fixed position while using limited amounts of fuel.

From L2, Euclid will observe galaxies as far as ten billion light years away, scanning more than one-third of the sky. The goal is for these observations to help scientists better understand the “dark universe.” Researchers have calculated that dark energy makes up about 68 percent of the cosmos and is responsible for accelerating the expansion of space. Dark matter, meanwhile, makes up 27 percent of the universe and holds galaxies together. But beyond that, astronomers don’t know much about these mysterious cosmic components.

An image of outer space showing distant stars and galaxies in a white color
A test image taken by Euclid's visible light instrument showing distant stars and galaxies. ESA / Euclid / Euclid Consortium / NASA, CC BY-SA 3.0 IGO

When Euclid’s scientific team turned on the visible light instrument for the first time, they found that sunlight was leaking into its images. But this only happens when the instrument is positioned at certain angles, so by avoiding those orientations, the team will still be able to image the universe, according to the ESA’s statement.

The test image from the telescope’s visible light instrument did not contain sunlight contamination. Though it covers a relatively small area of sky—roughly a quarter of the width and height of the full moon—it’s packed with detail. It shows a few galaxies very clearly, while others remain blurry.

But in the future, Euclid’s images will be even more detailed and sharper, according to the ESA. The current images are unprocessed, so they contain some unwanted components, such as streaks of cosmic rayshigh-energy particles that speed through space. Upcoming, science-ready images will have these removed.

“Each new image we uncover leaves me utterly amazed,” says William Gillard, instrument scientist for Euclid’s NISP, in the statement. “And I admit that I enjoy listening to the expressions of awe from others in the room when they look at this data.”

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