After a “perfect” takeoff on Saturday, Europe’s Euclid Space Telescope is headed for its vantage point, from where it will try to shed light on one of science’s greatest mysteries: dark matter and 95% of dark energy. of the universe but we know nothing about it.
The satellite lifted off from Cape Canaveral, Florida at 11:12 a.m. local time (Eastern Time) aboard SpaceX’s Falcon 9 rocket.
After separating from the rocket, it emitted its first signal, as expected.
The two-ton telescope will be placed 1.5 million kilometers from Earth. Scientific work should begin in about three months, once the calibration of the instruments is complete.
During a live video from the European Space Agency (ESA), its director general Joseph Aschbacher said, “It is a very gratifying moment to see this mission moving towards its destination.”
The launch was “perfect,” said ESA’s science director Carol Mundel. “Over the next six years, we will unravel the mysteries of the dark side of the universe. »
The probe draws a three-dimensional map of the universe, covering more than a third of the sky and containing billions of galaxies. Observed distant galaxies make it possible to go back in time by 10 billion years – the time it takes for their light to reach us.
Dark matter (25% of the universe) and dark energy (70%) have opposite effects: while first ensuring the convergence of galaxies, dark energy causes the expansion of the universe.
For the first, dark matter, we know that this is due to a mysterious observation: it is not possible to explain how a galaxy or a group of galaxies does not disperse by taking into account only the gravitational forces of their visible constituents (planets, stars, etc.). )
“You have to assume an extra amount of matter that’s invisible to our telescopes, like a gravitational force that holds everything together,” explains Michael Seifert, Euclid’s science manager for NASA, who is participating in the mission, to AFP.
This cosmic “cement” is called dark matter.
Not directly observed, according to some hypotheses, it may be subatomic particles.
Dark energy may be even more intriguing.
Since the famous astronomer Edwin Hubble’s discovery in the 1920s, we have known that the universe is expanding. Since the 1990s, this expansion has accelerated.
But this “indicates that at very large scales, gravity actually has a repulsive component that pulls things apart,” Seifert says. This force is dark energy, “one of the great mysteries of physics”.
The lack of knowledge about these two dark elements has been described as an “embarrassing situation” by Giuseppe Racca, head of the Euclid mission at ESA.
Therefore, the satellite aims to better understand their properties, how they function and how they evolve over time.
Thanks to its 3D mapping, the telescope will allow precise measurements of the distribution of galaxies and the expansion of the universe.
From these observations, dark matter and dark energy can be “implicitly” deduced, explained Giuseppe Rocca. Calculating dark matter can be done by “subtracting” visible matter.
Going back 10 billion years, Euclid was able to observe the first effects of dark energy, knowing that the acceleration of the universe’s expansion would have begun six billion years earlier.
At a cost of €1.5 billion, the European mission should last until at least 2029.
The telescope has two instruments: a visible-light (VIS) imager and a near-infrared spectroscopic-imager (NISP).
After being analyzed by about 2,600 researchers of the Euclid Consortium from about fifteen countries, the large amount of data collected will be available to the entire scientific community.
Named after the father of geometry, Euclid “would yield very useful data for many things besides cosmology,” recalls Mark Savage, astrophysicist and member of the Consortium on Atomic Energy Commission (CEA).
NASA also plans to launch a mission dedicated to exploring dark matter and dark energy in 2027, the Nancy Grace Roman Space Telescope.
Mark Savage judged these two tasks to be “complementary”. Making observations in different ways “allows us to make sure our measurement isn’t biased by something we don’t know,” he explained. The various tests conducted “are not sensitive to the same biases of unknown origin, and by overcoming them we obtain final answers”.