In the far reaches of space, planets, stars, our Milky Way and other galaxies are well known to us – at least some of them. However, two phenomena about which almost nothing is known so far play an extremely large part in the universe: dark matter and dark energy, invisible and extremely difficult to research. “Cosmology is in a situation that could be described as an embarrassment,” says Giuseppe Racca of the European Space Agency ESA.

He is program manager for “Euclid”. With this flying telescope, ESA wants to try to learn more about these factors that fundamentally influence our universe. Euclid is scheduled to launch into space from Cape Canaveral in the United States on July 1st. “Making the invisible visible” is how the French astrophysicist David Elbaz sums up the core of the mission.

The “Euclid” probe is about 4.7 meters tall, 3.5 meters wide and weighs just under two tons. Its high-resolution telescope, equipped with a visible and near-infrared camera, is expected to observe billions of galaxies. On its mission, the probe takes a look at the past of the universe and explores its development over the last ten billion years. Also, aim to create a 3D map where time is the third dimension.

Researchers hope that the mission will show how the universe has expanded and how individual structures have formed. From this they want to draw conclusions about dark matter and dark energy.

In the universe, astrophysicist Elbaz explains, there is more gravity than would be assumed based on the visible parts. “The Sun is spinning around the center of the Milky Way at such a high speed that it should erupt from the galaxy. And if it doesn’t erupt, that means it’s being attracted to another mass that we don’t see.” That is the dark matter. Dark energy, on the other hand, describes a kind of anti-gravity that makes galaxies seem to repel each other.

Originally, Esa wanted to shoot the enormously important probe into space with a Russian Soyuz rocket. However, because of the war of aggression against Ukraine and the sanctions that followed, Moscow withdrew its Soyuz rockets from the European spaceport in Kourou in French Guiana. The European Ariane 6, with which “Euclid” is also compatible, is not yet operational. It is not scheduled to complete its maiden flight until the end of the year. Now Esa is flying the telescope into space with a Falcon 9 from the US company SpaceX.

The 1.4 billion euro mission is initially scheduled for six years. The probe is to fly about 1.5 million kilometers into space, the way there will take about a month. After some tests, the mission should deliver the first images in the fall. Program manager Racca expects more data on extragalactic astronomy in the first year of the mission than there is from any other observations so far. “I expect that ‘Euclid’ will flood the scientific community with an unprecedented, massive amount of data.”

According to astrophysicist Elbaz, there could be a better understanding of dark matter for the first time about a year and a half after the launch of “Euclid”. But what kind of insights does the mission bring in the long term? “To know today what will be the impact of our better understanding of physics and of what ‘Euclid’ will tell us (…) is impossible.”

See the photo series from our archive: Satellites have a 24-hour view of the earth from space. They take their pictures from hundreds of kilometers up in the air and are sometimes very close.