2023-06-30 12:20:49
This is one of the greatest astronomical enigmas: the Universe is made up of 95% of two mysterious dark components of which we know almost nothing. The Euclid space probe will try to see more clearly. Its consortium brings together sixteen countries, including Switzerland, with a strong participation.
The mission of the European Space Agency (ESA) will take off Saturday at 11:12 am from Cape Canaveral in Florida, aboard a Falcon 9 rocket from SpaceX. In Switzerland, it will be 5:12 p.m.
ACCEPT MORE INFO
In his car, Mike looks in the direction of the Kennedy Space Center. This is where the Euclid satellite will be launched aboard a SpaceX Falcon 9 rocket on July 1, 2023. [Stéphanie Jaquet – RTS]The two-ton probe designed by Thales Alenia Space will launch to its final position, 1.5 million kilometers from Earth, at Lagrange Point 2, not far from where a celebrity is: the James Webb Space Telescope. From there, Euclid, named following the inventor of geometry, will draw up a three-dimensional map of the Universe, encompassing two billion galaxies over a portion of a third of the celestial vault, which is gigantic.
>> Read also: Lagrange points, a very attractive space destination
The third dimension of the map will be time: by capturing light from galaxies that have taken up to ten billion years to reach us, Euclid will delve into the past of the Universe, 13.8 billion years old. The satellite will make it possible to “build an image of these galaxies, which will reach us slightly deformed by the presence of matter between us and these galaxies that we observe”, explains Alice Gasparini, doctor in didactics of physics and specialist in cosmology in La Morning of the RTS.
“The biggest question that Euclid will try to answer is what is the nature of the most mysterious thing in the whole Universe, something that is not even matter: we don’t actually have no idea what it is”, explains Stéphane Paltani, from Florida where he went to witness the take-off of this probe on which he has been working for a dozen years.
“We gave the name ‘dark energy’, but that doesn’t mean anything, because we really don’t know what it is. Euclid is going to be the first experiment that will give us an indication of what it might be” . “Dark matter is a kind of gravitational presence. We’re not even sure it’s matter,” says Alice Gasparini.
>> See also the explanations of 7:30 p.m.:
The Euclid space telescope will make it possible to study the dark matter of the Universe that remains invisible to our eyes / 7:30 p.m. / 2 min. / yesterday at 7:30 p.m.
A puzzle from the 1930s
The history of the Universe will be reconstructed by cutting it into “slices of time”, hoping to detect the traces left by dark matter and dark energy over the formation of galaxies.
Dark matter and dark energy are of an unknown nature, but seem to govern the Universe, of which only 5% is composed of “ordinary” visible matter. “We see ‘ordinary’ matter, so to speak. So the matter we observe is matter that interacts with light”, explains Alice Gasparini.
“It absorbs, it emits or it reflects light, whereas most of the matter that makes up the universe simply ignores light”, continues the specialist in cosmology. “So we have no way to observe it other than by gravity and the effect that this matter has on space-time, therefore by the gravitational effect”.
Euclid mission leader Giuseppe Racca calls this misunderstanding of dark matter and dark energy a “cosmic embarrassment.” Without them, scientists cannot explain how the cosmos works. A puzzle that dates back to the 1930s, when Swiss astronomer Fritz Zwicky, observing the Coma cluster of galaxies, hypothesized that a significant part of its mass was invisible.
Almost 100 years later, the existence of this missing matter – called black (or dark) because it neither absorbs nor reflects light – is a consensus: “When we look at the tip of the iceberg there is something we don’t understand: everything is going too fast”, summarizes David Elbaz, member of the Euclid collaboration.
The rotation speed of stars within galaxies – including that of our Sun – is so high that they should be ejected, “like a rocket that tears itself away from Earth’s gravity and leaves”, explains this astrophysicist at the Commissariat to atomic energy. However, they remain there: “We deduce that there is an additional gravity which maintains them”, acting like a cement.
>> The full interview with Alice Gasparini in La Matinale: The guest of La Matinale (video) – Alice Gasparini, cosmology specialist and doctor in didactics of physics / The guest of La Matinale (in video) / 12 mins. / today at 07:33
The accelerating expansion of the Universe
At the end of the 1990s, astronomers detected a second anomaly, on the scale of the entire Universe: the galaxies are moving away from each other more and more quickly, under the effect of a repulsive force called dark energy.
This acceleration of the expansion of the Universe would have started six billion years ago. Going back ten billion years, Euclid might observe the first effects of dark energy and better identify it, the people who designed it hope.
But how to observe the invisible? By measuring its absence, by a warping effect called gravitational lensing: light from a distant object, such as a galaxy, is imperceptibly deflected by the visible matter and dark matter it encounters on the way to the observer.
“The light that comes to us from the galaxies observed by the satellite will be affected by this deformation of space-time, which will act as a lens, so it will really have a bezel effect”, explains Alice Gasparini. “This satellite will, by deforming the images received from these galaxies, reconstruct the characteristics of this telescope which is called a gravitational lens”, continues the doctor in didactics of physics. This gravitational lens will thus allow researchers to “observe” dark matter.
>> Read also: A space magnifying glass to measure the mass of a galaxy hosting a quasar
“By subtracting the visible matter, we can ‘calculate’ the presence of dark matter”, explains Giuseppe Racca.
“It is by watching this film of deformations in the history of the Universe that we will understand how dark energy behaves”, adds David Elbaz.
The scientist makes the comparison with a balloon on which lines are drawn with a marker to “see how quickly the balloon inflates” – which makes it possible to understand the effects of dark matter. As for the dark energy, it would be the breath that makes the balloon inflate.
On June 27, this last glimpse of ESA’s Euclid space telescope was taken just before it was encapsulated in a SpaceX Falcon 9 fairing: the nose of the rocket was installed above the spacecraft . [ESA – SpaceX]
“A gold mine for astrophysics”
Euclid has two instruments on board: a visible-light (VIS) imager and a near-infrared spectro-imager (NISP).
According to Yannick Mellier, this unprecedented cartography will constitute “a gold mine for astrophysics”, making it possible to study the shape of galaxies, the birth of clusters, black holes… And may help scientists to finally put the hand on the mysterious particle constituting dark matter, which escapes detection.
>> Read also: A gigantic black hole detected thanks to a gravitational lens
At a cost of 1.5 billion euros, the European mission must last until 2029 minimum.
Stéphanie Jaquet, from Florida, with AFP
>> See also the interview with Camille Bonvin, cosmologist at the University of Geneva:
Euclid Telescope: Dark matter discoveries will provide new insight into the Universe. The enthusiasm of Camille Bonvin, cosmologist at the University of Geneva / 7:30 p.m. / 2 min. / yesterday at 7:30 p.m.
1688128082
#Euclid #satellite #conquer #dark #side #Universe #rts.ch
