14 million galaxies, 500 times the area of the full moon and millions of stars in our Milky Way: the European Euclid mission is today publishing the first part of the sky map created by the space telescope. This 208-megapixel mosaic contains data from 260 observations made by the telescope over the course of just two weeks. This first, strip-shaped section of the sky already demonstrates the high data quality, from wide-angle panoramic views to the smallest structural details within individual galaxies. The mosaic represents about one percent of the sky survey that the Euclid Space Telescope will conduct over six years. The goal of the mission is to record galaxies and other celestial objects up to ten billion light-years away with such precision that astronomers can use them to learn more about dark matter and dark energy in space.
The European space telescope Euclid was launched in July 2023 to primarily collect data about the “dark side” of our universe: dark matter and dark energy. Their nature, mode of action and distribution are still largely unclear. In addition, previous observations have revealed discrepancies with common cosmological models that are difficult to explain, both in terms of matter distribution and cosmic expansion. The Euclid mission is intended to bring more clarity here. To do this, the telescope’s two instruments map the positions, structures and movements of galaxies and other celestial objects up to ten billion light-years away. The telescope is stationed at the Lagrange point L2, a stable position in space that is around 1.5 million kilometers away on the side of the Earth facing away from the sun. The telescope’s ability to image a large section of the sky in a single pass, but still sharply and at high resolution, makes Euclid particularly well suited for detailed yet comprehensive mapping. The first images published in November 2023 already demonstrated that the space telescope is working as hoped and living up to expectations.
A panoramic image with 14 galaxies
Now the European Space Agency (ESA) has presented the first large piece of the Euclid sky map at the International Astronautical Congress in Milan. The mosaic is based on 260 observations made by the space telescope between March 25 and April 8, 2024. In these two weeks, Euclid has already mapped 132 square degrees of the southern sky in high resolution – more than 500 times the area of the full moon. “This stunning image is the first part of a map that will cover more than a third of the sky in six years. Although it is only around one percent of the total map, it is full of diverse objects that will help scientists find new ways to describe the universe,” says Valeria Pettorino, Euclid project scientist at ESA.
The mosaic shows a good 14 million galaxies in a strip that stretches across the southern sky. The image is so detailed that you can zoom deep into the mosaic and then see the complex structure of a spiral galaxy. The distribution and structure of these galaxies can help detect the hidden influence of dark matter. To do this, astronomers will also use the weak gravitational lensing effect: If a large mass is present in the foreground of a distant galaxy – for example from a collection of dark matter – it distorts the light of the background galaxy in a certain way. These distortions can be used to determine how large the foreground mass is. The Euclid telescope makes these measurements possible thanks to its high resolution. The distance and redshifts of galaxies can reveal how quickly the universe is expanding. This allows conclusions to be drawn about dark energy, which is considered the “opponent” of gravity and the driver of cosmic expansion.
Just the beginning
The mosaic released today is just a taste of what is to come from the Euclid mission. Since the mission began scientific operations in February 2024, the telescope has already completed around twelve percent of its sky mapping – never before has an astronomical space mission provided so much data in such a short time. Euclid sends around 100 gigabytes of images and spectra to Earth every day – a challenge also for the data collection and processing infrastructure. To cope with this, the Euclid consortium has set up a European network of nine data centers, including the German Science Data Center (SDC-DE), which includes 7,000 processors and will process around ten percent of the data. “The constantly changing software and hardware presents our team with major challenges in ensuring timely processing,” explains Maximilian Fabricius from the Max Planck Institute for Extraterrestrial Physics, head of the German Science Data Center. “However, we are proud of how well everything now works together and that we are on the home stretch towards processing for the first public data release.”
Full data release for the first 53 square degrees of the survey, including a preview of the Euclid Deep Field areas, is expected to occur in March 2025. The cosmological data for the entire first year of the mission will be published in 2026.
Source: European Space Agency (ESA), Max Planck Institute for Astronomy