Sitting in a sterile hangar in Cannes, France, the European space telescope Euclid is still waiting to launch into space a few months later in an attempt to shed light on two of the great mysteries of the universe: dark matter and dark energy. These two invisible and theoretical elements make up 95 percent of the universe, but there is almost no data available on their exact nature, and this lack of knowledge is causing what mission leader Giuseppe Racca called “cosmic bewilderment.” Dark matter is thought to be one explanation for why galaxies have not dispersed into swarms of stars. As for dark energy, its presence is necessary to explain the acceleration of the expansion of the universe. In an effort to unlock these mysteries, the European Space Agency’s mission will map the universe in 3D, including two billion galaxies over a third of the apparent sky. Time will be the third dimension of the map. By capturing the light from galaxies that took 10 billion years to reach Earth, the Euclid telescope will plunge into the distant past of the universe, which was born 13.8 billion years ago. This week, the media got their first look at the two-ton vehicle, measuring 4.7 meters high and 3.5 meters wide, in the clean and sterile hangar of Thales Alenia Space in Cannes, France.
Measurement of absence The telescope will undergo a few additional tests before being transferred to the “Cape Canaveral” center in Florida, USA, from which it is expected to be launched on the “Falcon 9” rocket produced by “SpaceX” between the first of next July and the thirty of it. The vehicle was originally intended to carry a Russian Soyuz missile, but this plan was abandoned due to sanctions imposed on Russia. Euclid will be stationed near the James Webb Space Telescope, 1.5 million kilometers from Earth, ensuring that it will be exposed to the sun by means of its solar panels. The European telescope is supposed to broadcast its first images next October, but making discoveries will take much longer, as this must analyze the huge amounts of data that it will provide. And Giuseppe Racca predicted that the European mission, which cost 1.5 billion euros, would continue until 2029, and might be extended for a few more years, “unless anything unusual happens.” This telescope, named after Euclid, the mathematician who has been called the “father of descriptive geometry”, will be able to observe the invisible by measuring its absence. The light emanating from a very distant object, such as a galaxy, is imperceptibly deflected by the visible and dark matter that it encounters on its way to the observer, and this is what constitutes the effect of a weak gravitational lens.
Inaccurate knowledge “Subtracting the visible matter makes it possible to calculate the amount of dark matter between” the distant object and the rover, Giuseppe Racca explained. Euclid was provided with two tools for this purpose, the first of which was a telescope with a diameter of 1.2 meters, and a spectrometer and infrared light. Euclid has a peculiarity in that the width of its observing field is equivalent to the surface of “two full moons”, as explained by David Elbaz, an astrophysicist at the Atomic Energy Commission. This field enables him to identify huge structures, such as black holes, that the James Webb telescope cannot identify because “its field of observation is very small,” said René Lorig, scientific director of the project. It is hoped that Euclid will contribute to providing more data about the universe, as knowledge about it still lacks accuracy. For example, there have been two very accurate measurements of the expansion rate of the universe, but they currently give different answers. This week, the James Webb telescope discovered six galaxies much more massive than expected, dating back to the early ages of the universe (between 500 and 700 years after the Big Bang). And the new European telescope may be “the only tool” capable of answering these questions, according to David Elbaz.
