(Cannes) The European space telescope Euclid still rests in a sterile room, in Cannes, decked out in a sun-colored dress. In a few months, he will launch into space to try to shed light on two great mysteries of the universe: dark matter and dark energy.
Posted at 11:08 p.m
Daniel Lawler Agence France-Presse
These two elements, purely theoretical and invisible, make up 95% of the universe, but we know almost nothing about their exact nature. A lack of knowledge that the head of the mission, Giuseppe Racca, calls a “cosmic embarrassment.”
Dark matter is said to explain, among other things, why galaxies do not dissolve into swarms of stars. As for dark energy, its existence is necessary to explain the acceleration of the expansion of the universe.
In an attempt to lift the veil on these mysteries, the European Space Agency (ESA) mission will create a three-dimensional map of the Universe, spanning two billion galaxies over part of a third of the visible sky.
The third dimension of the map will be time. Because by capturing the light of galaxies that have taken up to ten billion years to reach us, Euclid will delve into the distant past of the universe that was born 13.8 billion years ago.
The two-tonne ship, 4.7 meters high and 3.5 meters wide, was presented to the press for the first time this week in a sterile white room at the Thales Alenia Space group in Cannes.
measure absence
He will undergo a handful of tests before heading to Cape Canaveral, Florida. The launch is scheduled to take place between July 1 and 30 on a SpaceX Falcon 9 rocket. The originally planned flight with a Russian Soyuz rocket was canceled due to sanctions against Russia after its invasion of Ukraine.
Euclid will reach a position close to that of the James Webb Space Telescope, 1.5 million kilometers from Earth, guaranteeing it permanent exposure to the sun through its solar panels.
Its first images are expected in October next year, but after analyzing the mountains of data that Euclid will provide, it will take much longer for discoveries.
The European mission, which will cost 1.5 billion euros (CAN$2.15 billion), must last until 2029, with a few bonus years “if nothing unusual happens,” explained the mission leader.
How will Euclid – who owes his name to the father of geometry – go about observing the invisible? By measuring his absence.
Light from a very distant object like a galaxy is subtly deflected on its way to the observer by the visible matter and the dark matter it encounters. This is the weak gravitational lensing effect.
Shaky understanding
“By subtracting the visible matter, we can ‘calculate’ the presence of dark matter that is between the distant object and the observer,” explains Giuseppe Racca.
For this, Euclid has two instruments: a 1.2 meter diameter telescope and an infrared spectrometer and photometer (NISP).
Euclid has the peculiarity of the width of its observation field, which corresponds to the surface of “two full moons,” says David Elbaz, astrophysicist at the CEA.
This field will allow Euclid to locate massive structures – like black holes – that the James Webb telescope can’t identify because “its field of view is too small,” the project’s principal investigator, Rene Laureijs, tells AFP.
Our understanding of the universe remains flawed. For example, two very accurate measurements of the universe’s expansion rate currently give two different answers: an inconsistency called the Hubble voltage, which may involve dark energy.
And this week, the James Webb telescope discovered six much more massive than expected galaxies in the distant ages of the Universe (between 500 and 700 million years after the Big Bang).
According to David Elbaz, Euclid may be “the only tool” capable of answering these questions.