EUCLID reveals its stunning first images of the cosmos


Monday, July 31, the EUCLID telescope of the European Space Agency (ESA) sent its first images. While these initial shots are certainly fascinating, they also confirm that the instruments of the space observatory are working perfectly.

The success of Euclid so far is truly exciting. The purpose of this machine is to map the dark side of our universe. Billions of galaxies residing up to about 10 billion light-years away will be analyzed. The agency even claims that this ambitious map will be in 3D. It will include the element of time to show how the dark side has evolved in tandem with a maturing cosmos.

“The extraordinary first images obtained using Euclid’s visible and near-infrared instruments open a new era for observational cosmology and statistical astronomy” said (ref.) Yannick Mellier, an astronomer head of the Euclid Consortium. “They mark the beginning of the search for the true nature of dark energy”. Euclid was launched on July 1 from Cape Canaveral in Florida. Positioned about 1.6 million km from Earth, it joined the James Webb Space Telescope on July 28 at what is known as the second Lagrange point. In the coming months, scientists will continue to test the machine until it officially begins its cosmic investigations.


The images below were taken with an instrument on Euclid called VIS (Visible Instrument). As the name suggests, VIS captures the universe through the visible electromagnetic spectrum between 550 and 900 nanometers. On the left is the full field of view of VIS, while on the right is an enlarged version.

The first images taken by EUCLID's instrument called VIS. On the left, the entire field, on the right, the enlargement.
The first images taken by EUCLID ‘s instrument called VIS. On the left, the entire field, on the right, the enlargement. Credit: ESA

Some highlights of the VIS portraits include cosmic rays, a myriad of twinkling stars, and some blurred spots. Those blobs, the ESA explains, are galaxies that Euclid will further investigate as it develops a highly detailed map of our universe, dark energy, and everything else. “Ground tests don’t give you images of galaxies or star clusters, but they’re all here in this field” said Reiko Nakajima, a scientist from the VIS instrument. “It’s beautiful to look at, and it’s a joy to do so with the people we’ve worked with for so long”.

The other instrument is called NISP (Near-Infrared Spectrometer and Photometer). As ESA states, NISP has two roles. Firstly, it can visualize galaxies in the infrared light, invisible to the human eye, between about 950 and 2020 nanometers. The James Webb Space Telescope also uses such infrared wavelengths. Secondly, NISP can accurately measure the amount of light emitted by each galaxy. This value can tell us how far away those galaxies are.

The first images taken by EUCLID's instrument called NISP. On the left, the entire field, on the right, the enlargement.
The first images taken by EUCLID ‘s instrument called NISP. On the left, the entire field, on the right, the enlargement. Credit: ESA

A third image

The NISP images are quite similar to the VIS set, as the left side includes the full field of view of NISP, while the right side shows an enlarged section. But before reaching the NISP detector, the deep-space light captured by Euclid also passes through some fantastic filters. These filters can do things like measuring brightness at a specific infrared wavelength, which helps with NISP’s measurements of galactic distance.

“While these first test images are not yet usable for scientific purposes, I am delighted that the telescope and the two instruments are now working superbly in space,” said Knud Jahnke of the Max Planck Institute for Astronomy (MPIA), who works on Euclid. Indeed, one of these filters is the reason why NISP has provided us with a third test image.

Le prime immagini riprese dallo strumento di EUCLID chiamato GRISM.
The first images taken by EUCLID ‘s instrument called GRISM. Credit: ESA

In addition to looking like a screensaver, this image is important because each stripe represents an individual light spectrum from a galaxy or star. Euclid has a device known as a GRISM that can essentially split cosmic light into a complete spectrum of wavelengths before sending the data to NISP. With this process, scientists can determine how far away a certain galaxy is, for example, and what the galaxy is chemically composed of.

“We have seen simulated images, we have seen laboratory test images” said William Gillard, a scientist from the NISP instrument. “It is still hard for me to grasp that these images are now the real universe. So detailed, simply fantastic”.

Dark energy & dark matter

Dark energy and dark matter constitute some of the biggest and most fascinating questions in astronomy today. Neither phenomenon can be seen by human eyes, yet they seem to hold the universe together. Space is constantly expanding outward in every direction, but the strange thing is that it appears to be happening at speeds that scientists can’t account for based on what we see. So, something else must be acting to accelerate cosmic expansion. Scientists call that “something” dark energy.

Meanwhile, within the universe, there seems to be a sort of glue that ensures galaxies are held in place and determines how they are arranged. Presumably, this is because some kind of invisible material surrounds the galaxies and thus exerts gravitational forces on them. That invisible “glue” is known as dark matter. All we know for certain at this moment is that the dark universe exists.

EUCLID’s future

If EUCLID’s mission to map the universe over the next six years or so is successful, perhaps scientists will get some clues about what the dark universe truly is. This is because, as dark matter and dark energy interact with things in space, delineating the distribution and evolution of cosmic objects can tell us where the dark universe fits into the story.

“I have full confidence that the team behind the mission will use Euclid to reveal so much about the 95% of the universe that we currently know so little about” said Josef Aschbacher, the Director-General of ESA. “After more than 11 years of designing and developing Euclid, it is exhilarating to see these first images” said Giuseppe Racca, Euclid’s project manager. “It’s even more amazing when we think that we are seeing only a few galaxies here, produced with minimal fine-tuning of the system. The fully calibrated Euclid will eventually observe billions of galaxies to create the largest 3D map of the sky ever seen”.

Stefano Gallotta
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