Understanding all about the mysteries of dark matter and dark energy, to be studied by the European Euclid Expedition

This is one of the great challenges of modern physics. The European Euclid Space Telescope is scheduled to lift off Saturday, July 1, with a SpaceX Falcon 9 rocket in an effort to unlock the mysteries of dark matter and dark energy.

>> Continue to launch Euclid’s mission into our lives

What exactly is it? We still know almost nothing about her. However, dark matter and dark energy, according to scientists’ estimates, make up 95% of the universe. Ordinary matter, which we know, and which is in the stars, in the planets, of which we are composed, is only 5% of the total. The mission promises to be enormous, and the European Space Agency (ESA)-led mission could mark the history of cosmology.

What is Euclid’s task?

space telescope It will scan a third of the sky for at least six years, from a point – called the Lagrangian point 2 – located 1.5 million kilometers from Earth. His mission: to create a 3D map of the universe. Its field of observation is particularly wide. To visualize the vast area covered by Euclid, the European Space Agency has produced this graph which shows (in grey) the regions to be observed.

Using his instruments (a 1.2-meter diameter telescope in the visible and an infrared spectrometer), Euclid will survey 12 billion celestial bodies to identify the massive structures. In the universe, matter is not evenly distributed. It is organized around a cosmic web, which is a web of filaments of gas and dark matter “occupies the entire volume of the universe”sums up The Atomic Energy and Alternative Energy Authority (ECA). Its structure may resemble that of a sponge or neural networknotes astronomer Bruno Altieri, scientific director of the Euclid mission at the European Space Agency.

To try to get an idea of ​​the scale of this painting, you have to picture yourself at giant scales. In the canvas, intersections of threads and empty areas coexist. At the junctions are clusters and superclusters of galaxies, the most massive groups in the universe. For example, the Milky Way, our galaxy, is part of a giant group called Laniakea, which is located at the crossroads of filaments. “If Earth is your flat, the solar system is your city, the Milky Way your neighborhood and Laniakea your continent”Blog explains around the sky.

>> What is Laniakea, the giant celestial continent where our galaxy rotates?

Euclid’s measurements should make it possible to understand how the cosmic web evolves over time under the influence of dark matter and dark energy. In fact, the telescope will be watching very far away, so it will go back in time, observing as much as 10 billion years (the Big Bang happened 13.7 billion years ago).

What is dark matter and dark energy?

Classical matter, which we know and which makes up us, occupies only 5% of the entire universe. Dark matter occupies 25% and dark energy 70%.

dark matter. Although there is five times more dark matter in the universe than classical matter, dark matter is invisible and undetectable. What scientists have realized since the 1930s are its effects. They found that stars and galaxies are moving much faster than models predict. To explain what they are measuring, they estimate that an invisible mass is at play, and this matter, which escapes our observing instruments, is what is called dark matter.

dark energy. It is highlighted In 1998 when scientists discovered that the expansion of the universe is accelerating. It was a surprise at the time, because the scientific world had never expected such an outcome. To explain this unexpected observation, a new parameter had to be introduced, which scientists called dark energy (or dark energy), to which the acceleration of the expansion of the universe is attributed. The three astrophysicists who conducted this work were awarded the Nobel Prize in Physics in 2011.

How do dark matter and dark energy work?

Don’t confuse dark matter with dark energy. The two are not from the same family, even “adversaries”According to Bruno Altieri. Dark matter has a gravitational effect: its mass creates the gravitational force. On the scale of the universe, it should act as a brake on its expansion.

its dark energy “repellent effect”. Because of them, the celestial bodies are repelled from each other, moving away from each other. In the expansion of the universe, if dark matter is likened to the brakes, dark energy acts as an accelerator. And she is that “Dominates the expansion of the universe for a few billion years.”Bruno Altieri explains.

The names “dark matter” and “dark energy” do not imply that the two concepts are related. They are named for lack of a better one. The term “lion” actually refers to the dark mystery that still surrounds them because we know neither their origin nor their nature.

“When we talk about ‘dark matter’ or ‘dark energy’, we are masking our ignorance with the word ‘darkness’.”

Bruno Altieri, astronomer

at franceinfo

We really don’t know anything about them?

Scientists are not at a complete standstill. They throw ideas and formulate hypotheses. But no one stands out and manages to come to a consensus.

dark matter. It still keeps all its secrets despite the intense efforts of scientists all over the world. where are you from ? “We do not know”responds to Françoise Combes. “We don’t even know what it is.”Honestly, lose the astrophysicist world. In fact, the particles that can form them remain unknown. Certainty: dark matter It does not emit or interact with light.Françoise Combes notes.

“Dark matter is transparent and can be all around us without us seeing it.”

Françoise Combes, astrophysicist

at franceinfo

dark energy. His recent discovery and elusive side mean he’s still being studied quite a bit. “Energy is everywhere, spreading”As Françoise Combes says: “Nobody knows what it’s made of, or even if it’s a form of energy!” Whoops ESA.

How will Euclid’s task help them understand them better?

Dark matter can be observed indirectly through its effects. The high density of matter can deflect light: we are talking about a “gravitational lens”. This phenomenon distorts what we perceive of certain things. Shown in the first published image from the James Webb Telescope: the galaxies appear flat, frayed, and arc-shaped, due to the enormous density of the white galaxy cluster in the center of the image.

with Euclid, “We’re going to study weak distortions and create statistics for billions of galaxies.”Bruno Altieri explains, making it possible to map dark matter. By analyzing the evolution of the cosmic web, scientists will also be able to estimate the period when the expansion of the universe began to accelerate. “We’ll have answers to questions like: ‘Is dark energy constant over time?'” or “Does it differ?” Defines Françoise Combes. According to the astrophysicist, the first question should be answered with Five to ten years..

If we don’t know anything about what makes up 95% of the universe, does that mean we’re doing it wrong?

The implications of the potential discoveries of Euclid’s mission could call into question the standard cosmological model and Einstein’s still-relativistic theory of relativity. Our understanding of gravity may not be perfect.Bruno Altieri confirms. And imagine: “In the same way that Einstein’s physics incorporated Newtonian physics into a larger theory, we may have misunderstood something and need to develop a larger theory.”

“Either we discover new particles [pour la matière noire], or we will change the laws of physics. It’s still basic.”

Françoise Combes, astrophysicist

at franceinfo

From the first year, Euclid’s readings will constitute a mass of data as important as all of ESA’s science missions for twenty-five years, Bruno Altieri asserts. To unravel the mysteries of these phenomena, scientists will have to use their gray matter and possibly spend a few sleepless nights there.