The Euclid space telescope, launched in July 2023, is expected to create the most comprehensive map of the “dark” cosmos to date over the course of its six-year mission. Now the European Space Agency ESA has published the first scientific images from the telescope. They demonstrate the performance of the 1.2-meter telescope stationed 1.5 million kilometers from Earth at Lagrange point 2. Its special feature is that it can image a large section of the sky in high resolution and sharpness in just one pass. By mapping the cosmos in infrared and visible light, Euclid aims to help unravel the influences of dark matter and dark energy in the universe.
The main task of the Euclid Space Telescope is to shed light on how the two “dark” components of the cosmos – dark matter and dark energy – made our universe what it is today. While dark matter influences the distribution of galaxies, galaxy clusters and other large structures in the cosmos through its gravitational effect, dark energy - if it exists - is considered an opponent of gravity. This mysterious, unproven force is said to drive the expansion of the cosmos and is responsible for the accelerated expansion of space. However, the nature of these two “dark ingredients” of the universe is still completely unclear. In addition, previous mapping of the distribution of matter and measurements of cosmic expansion have revealed some discrepancies that are difficult to explain using current models.
Fast and high resolution at the same time
“Euclid will allow cosmologists to study the two competing dark mysteries together for the first time,” says ESA Science Director Carole Mundell. To help solve these cosmic mysteries, the Euclid Space Telescope, launched on July 1, 2023, will map the expansion rate and mass distribution in the cosmos over the last ten billion years. What sets Euclid apart from other telescopes is its ability to image a large section of the sky sharply and with high resolution in just one pass. This makes this telescope particularly suitable for mapping the cosmos. “At the end of his six-year mission, Euclid will have observed 14,000 square degrees – 35 percent of the entire sky,” explains Maximilian Fabrizius from the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching and at the Ludwig Maximilians University (LMU) in Munich. In combination with image data from ground-based telescopes, the aim is to create the largest and most precise multi-wavelength catalog in extragalactic astronomy.
For this task, the Euclid Telescope is equipped with two scientific instruments, the Visible Instrument VIs and the near-infrared spectrograph and photometer NISP. With VIS, Euclid will measure the weak gravitational lensing effect and use it to map the distribution of mass: If a large mass is present in the foreground - for example a collection of dark matter - it distorts the light from the background galaxies in a certain way. These distortions can be used to determine how large the foreground mass is. Thanks to its sensitivity in the near-infrared range, the NISP spectrometer can look back into the early cosmos and measure the redshift and thus the exact distances and distances of the galaxies. This provides information about the expansion of the universe.
The first five shots
After a test and calibration phase lasting several months, the Euclid telescope has now taken the first five scientific images and sent them to Earth. They demonstrate that the telescope fully meets the expectations placed on it: “We have never seen astronomical images as detailed as these before,” says Euclid project scientist René Laureijs from ESA. “They are even more beautiful and sharper than we had hoped and show us many previously unrecognized features in well-known areas of the nearby universe.” One of these images shows the Perseus galaxy cluster, around 240 million light-years away, one of the most massive structures in the entire universe. With just one glance, the Euclid telescope has imaged a thousand of the galaxies belonging to the Perseus cluster and also shows 100,000 additional galaxies from the vicinity of this cluster. “With Euclid’s huge field of view and its high sensitivity, the galaxies in the Perseus galaxy cluster can be measured down to their outermost and faintest regions,” says Matthias Kluge from MPE.
Another image shows the globular star cluster NGC 6397, which is around 7,800 light-years away. These structures made up of thousands of stars bound together by gravity are among the oldest objects in the cosmos. “Euclid is currently the only telescope that can record an entire globular cluster at once and still sharply display even the faintest stars in its outer regions and separate them from the cosmic background,” explains Davide Massari from the National Institute for Astrophysics in Italy. The interaction of globular clusters with their galaxies and their movements can reveal more about the distribution and influences of dark matter. Globular star clusters are also interesting because they are considered building blocks for early, irregularly shaped galaxies. One such irregular galaxy, NGC 6822, is therefore Euclid's third image. The telescope also captured the spiral galaxy IC 342, which is around eleven million light-years away, and the famous Horsehead Nebula in the constellation Orion.
“The early data from Euclid are breathtaking!” comments Koshy George from LMU Munich. “With the large field of view, clarity and sensitivity of the VIS and NISP instruments, we can discover many new details around the galaxies over a wider range than was previously possible.” This means that the Euclid telescope is already in its first Pictures prove that it more than meets the high expectations placed on it. As the ESA announces, a few final adjustments will now be made to the space telescope before routine scientific operations begin at the beginning of 2024. During the course of the mission, new data sets will be published once a year.
Source: European Space Agency (ESA), Max Planck Institute for Astronomy