The Horsehead Nebula and other stunning scenes highlight the talents of the just-launched Euclid mission. The telescope will reach into the depths of the cosmos to understand dark matter and dark energy.

This square astronomical image is divided horizontally by a waving line between a white-orange cloudscape forming a nebula along the bottom portion and a comparatively blue-purple-pink upper portion. From the nebula in the bottom half of the image, an orange cloud shaped like a horsehead sticks out. In the bottom left of the image, a white round glow is visible. The clouds from the bottom half of the image shine purple/blue light into the upper half. The top of the image shows the black expanse of space. Speckled across both portions is a starfield, showing stars of varying sizes and colours. Blue stars are younger and red stars are older.
Euclid shows us a spectacularly panoramic and detailed view of the Horsehead Nebula, also known as Barnard 33 and part of the constellation Orion. In Euclid’s new observation of this stellar nursery, scientists hope to find many dim and previously unseen Jupiter-mass planets in their celestial infancy, as well as young brown dwarfs and baby stars.
ESA / Euclid / Euclid Consortium / NASA, image processing by J.-C. Cuillandre (CEA Paris-Saclay), G. Anselmi; CC BY-SA 3.0 IGO

Eat your heart out, JWST. The European Space Agency (ESA) has published the first color images obtained by the Euclid space telescope, and they’re gorgeous.

With its 1.2-meter primary mirror, Euclid is less powerful than the James Webb Space Telescope, but its field of view is about 200 times as large. As a result, each Euclid image covers an area more than twice the size of the full Moon, while the angular resolution is about 0.2 arcseconds.

“The images are thrilling and are a testament to the hard work by the Euclid team over the past many years,” comments Julie McEnery (NASA Goddard), the project scientist for NASA’s future Roman Space Telescope, to be launched in 2027. “Congratulations!”

Like an astronomical Sherlock Holmes, Euclid will try to solve (or at least shed more light on) the two biggest conundrums in cosmology: dark matter – the mysterious stuff that keeps galaxies from flying apart – and dark energy, the puzzling force behind the accelerating expansion of the universe.

Launched on July 1st, Euclid will now map the 3D distribution of 1.5 billion galaxies out to distances of 10 billion light-years. This map will reveal the evolution of the large-scale structure of the universe, which is governed by both dark matter and dark energy.

Meanwhile, precision measurements of the shapes of galaxies will yield information on the distribution of dark matter. These shapes are affected by weak gravitational lensing – small distortions caused by the gravity of intervening matter, both luminous and dark.

“The quality of these first images is really great,” says cosmologist Henk Hoekstra (Leiden Observatory, The Netherlands), a member of the Euclid Science Coordination Group. “Everything suggests that Euclid will perform even better than expected, and that the mission will reach its scientific goals.”

What the First Images Hold

A big spiral galaxy is visible face-on in white/pink colours at the centre of this square astronomical image. The galaxy covers almost the entire image and appears whiter at its centre where more stars are located. Its spiral arms stretch out across the image and appear fainter at the edges. The entire image is speckled with stars ranging in colour from blue to white to yellow/red, across a black background of space. Blue stars are younger and red stars are older. A few of the stars are a bit larger than the rest, with six diffraction spikes.
One of the first galaxies that Euclid observed is IC 342, nicknamed the "Hidden Galaxy." Thanks to its sharp infrared view, Euclid has already uncovered crucial information about the stars in this galaxy, which is a look-alike of our Milky Way. The galaxy is 11 million light-years away in the constellation Camelopardalis.
ESA / Euclid / Euclid Consortium / NASA, image processing by J.-C. Cuillandre (CEA Paris-Saclay), G. Anselmi; CC BY-SA 3.0 IGO
A close-up image shows many background galaxies that lie much farther away than the nearby IC 342.
ESA / Euclid / Euclid Consortium / NASA, image processing by J.-C. Cuillandre (CEA Paris-Saclay), G. Anselmi; CC BY-SA 3.0 IGO

Euclid has targeted the famous Horsehead Nebula in Orion; a nearby globular cluster (NGC 6397); two galaxies (NGC 6822 and IC 342); and the Perseus galaxy cluster. This last image not only shows some 1,000 cluster members, but also a whopping 100,000 remote background galaxies.

This square astronomical image shows thousands of galaxies across the black expanse of space. The closest thousand or so galaxies belong to the Perseus Cluster. The most prominent members of the cluster are visible in the centre of the image and appear as large galaxies with haloes around them in yellow/white, comparable to streetlamps in a foggy night. The background of this image is scattered with a hundred thousand more distant galaxies of different shapes, ranging in colour from white to yellow to red. Most galaxies are so far away they appear as single points of light. The more distant a galaxy is, the redder it appears.
This incredible snapshot from Euclid is a revolution for astronomy. The image shows 1000 galaxies belonging to the Perseus Cluster, and more than 100 000 additional galaxies further away in the background. Many of these faint galaxies were previously unseen. Some of them are so distant that their light has taken 10 billion years to reach us. By mapping the distribution and shapes of these galaxies, cosmologists will be able to find out more about how dark matter shaped the universe that we see today.
ESA / Euclid / Euclid Consortium / NASA, image processing by J.-C. Cuillandre (CEA Paris-Saclay), G. Anselmi; CC BY-SA 3.0 IGO
Perseus cluster close-up
A close-up shows some of the thousands of background galaxies that Euclid caught in its image of the Perseus Cluster.
ESA / Euclid / Euclid Consortium / NASA, image processing by J.-C. Cuillandre (CEA Paris-Saclay), G. Anselmi; CC BY-SA 3.0 IGO

According to Hoekstra, images like these enable much more science than just cosmology. “For instance, because of Euclid’s large field of view, we may easily discover rare objects, like young solitary brown dwarfs in star-forming regions,” he says. “You can never find those with JWST.”

Euclid’s project scientist René Laureijs (ESTEC, The Netherlands) is particularly happy with the very dark background in the images. Shortly after launch, it turned out that Euclid suffered from stray light entering the telescope, but this problem has been successfully remedied by avoiding certain orientations with respect to the Sun. “Apparently, we’ve done a good job,” says Laureijs.

What's Coming

Euclid’s nominal six-year survey, which will cover about one-third of the full sky, will start in late January or early February next year, says Laureijs. The first science data probably won’t be released before 2026, “but every now and then, we will publish the most beautiful images from the survey.”

In a complementary mission, NASA’s Roman Space Telescope will also make 3D maps of the distant universe and study gravitational microlensing, but with a telescope 2.4 meters in diameter. “Roman will have greater sensitivity but will survey a much smaller region of sky,” says the mission’s project scientist McEnery.

Moreover, she says, “in regions where our surveys overlap, Roman will be able to search for objects that have evolved since the time of the Euclid observations. The superb angular resolution of Euclid and Roman coupled with their wide-angle vision will give us an unprecedented view of the dynamic universe.”

As for cosmology, adds Roman’s deputy project scientist Jeffrey Kruk (NASA Goddard), “Euclid’s wider area survey will excel at lower redshifts [corresponding to closer distances], while the greater depth of the Roman survey will probe to higher redshifts [farther distances]. The combination of the two datasets will be more powerful than either on its own.”


Image of Bob-dBouncier


November 7, 2023 at 9:44 am

Space is looking less empty!

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Image of Lou


November 9, 2023 at 7:31 am

Wowser, it's like 2MASS on steroids! Just insane what you can do in space with a mere 1.2m telescope...

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