Thousands of European scientists, and around the world, are impatient to see the new space telescope of the European Space Agency (ESA) take off, from which they expect new truths, because what we know is too little. Euclid will take off in early July from Cape Canaveral, aboard a SpaceX Falcon 9, it will reach a point 1.5 million kilometers away from Earth. From there, the Lagrangian point L2 will scan the sky to better understand that part of the Universe silent to all our instruments which has the names of dark matter and energy. Euclid is a Medium-class mission of the European Space Agency, with a large Italian contribution, together with France and the United Kingdom. It is one of the big events in the European space this year alongside the launch of Juice, bound for Jupiter, in April.
The 3D map of the cosmos
We will ask Euclid for answers to two of the questions that have been puzzling scientists for decades. It is that piece of Cosmos that cannot be seen but seems to be there and to which we have given the name of dark energy and dark matter. The former seems to be responsible for accelerating the expansion of the Universe, the latter does not emit electromagnetic radiation, photons (as ordinary matter does), it is therefore invisible to all our instruments, but it is found in the movement of galaxies and in the effects of their gravitational field.
“It’s an embarrassing situation for the cosmology of this millennium,” he explained Joseph Raccaproject manager of the mission – to see that everything we know, what we are made of, is all contained in the 5 percent of what is in the Universe. 95% is something else. It is among the main subjects that science has to deal with, understanding what the Universe is made of”.
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Euclid’s task is simple to explain: thanks to his 1.2 meter diameter mirror, he will have to observe with great precision how all the mass that can be seen is distributed. And from this infer how the dark one behaves. Euclid has a large field of view to map a third of the sky, almost all that not occupied by our galaxy: “To study the Universe you have to look at a large part of it – added Racca – it will make a more detailed scan of 36 percent of the whole sky in six years, if that seems like a long time, consider that Hubble would take a thousand. Because Euclid has a ‘wide angle’, which covers two and a half times the surface of the Moon”. It is essential to be able to make a 3D map of the visible Universe and thus have statistically significant observations to deduce how everything has been distributed since the Big Bang to today, in over 13 billion years.
The mystery of matter and energy
On board there are two instruments, Vis (Visible instrument) and Nisp (Near infrared spectrometer photometer), respectively for recording light in the visible wavelengths (those to which the human eye is also sensitive) of over a billion galaxies, and in the near infrared, to also study the spectrum, the composition of light, of millions of these objects. On the other hand, very complex calculations will come from his observations, starting from the name of the phenomenon. For example, to study the weak gravitational lensing, the almost imperceptible distortion of light from deep-sky objects by galaxies closer to us, as predicted by General Relativity, and the effects ofbaryonic acoustic oscillation: “All matter deforms the path of light – reflects Racca – we see a distant galaxy deformed by visible and invisible matter, if we subtract the effect of the visible one, we get the effect of the dark one. Galaxies , moreover, they are not evenly distributed, but grouped in clusters, voids and filaments. This distribution tells us the relationship between the expansion caused by dark energy and the attraction due to gravity. And we could also find that gravity, at the level cosmic, on a very large scale, does not work as General Relativity explains”.
All this will therefore lead to new considerations regarding how the Universe has evolved. And maybe a more precise definition of the Hubble constant of expansion of the Cosmos. Indeed, Euclid will observe galaxies in the last ten billion years, from the time when the expansion seems to have accelerated. After the launch, he will follow a commissioning phase, to verify that everything works, after a month the whole phase of calibrations and tests will start. “In September-October we will start with the first observations and by November we think we will be able to disclose the data of the early release – anticipated Racca – six observations planned to show what Euclid is capable of doing”.
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Euclid is big eats a minivan and weighs about as much, two tons. The total investment is approximately 1.4 billion. ESA contributed 852 million from the compulsory scientific program (Italy is the third contributor with just under 12 percent), 428 million came from the scientific consortium (about 80 from Italy through the Space Agency). The rest from NASA. But to manage all the data that Euclid will rain down in the next few years, a great international collaboration will be needed to analyze the data on the Earth: “A fundamen fundamental questions: where did the antimatter go? And why do we have three families of particles?”.
The Italian role in the large international consortium
The tools and the Scientific ground segment (Sgs), are designed and managed by a European consortium made up of 2,500 scientists from over one hundred institutes in thirteen countries: “It is one of the largest consortiums in the world, Italy is the second contributor after France to the activities of the scientific consortium – Anna Maria Di Giorgio, technical-scientific coordinator of the ASI-INAF agreement to support activities for the Euclid mission, pointed out – we are at the forefront in the world, our scientists will become a point of reference worldwide for studies on fundamental cosmology”.
About 35 percent of Euclid’s industrial contracts go to Italian companies. Including that of the construction of the same spacecraftcreated by Thales Alenia Space: “It is a great result, it is by far the country with the greatest return – underlined Barbara Negri, head of ASI Human Flight and Scientific Experimentation – she is responsible for the ground segment, the heart of the mission. The “The goal is so lofty and ambitious that everything must work in a very precise manner, above all to interpret indirect information and find out if this cosmological model, which is in crisis, is valid or needs to be corrected. This is why we put scientific excellence on track and Italian technology”.
Italy has several important tasks. How to coordinate the entire SGS, through INAF, which also created the on-board software for the two instruments supported by the Italian Space Agency. And he has direct responsibility for one of the nine Science data centers, the construction of which was entrusted to Altec by ASI, and for verifying the performance of the Nisp tool and data quality. Our country also manages the planning of all the observations and contributes to the definition of the requirements and the preparation of the data analysis. ASI, in collaboration with Inaf and Infn, led the industrial team that designed and created the contributions to the instruments, a Temporary Association of Companies with Ohb Italia and Sab Aerospace and Temis. while the leadership for the construction of the platform, the satellite, was entrusted to Thales Alenia Space Italia.
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In total, 20 countries plus the United States participated: “The industrial part has a very strong Italian component, it wasn’t easy because the competition was great – said Walter Cugno, exploration and science manager at Thales Alenia Space – 80 companies took part companies with 140 supply contracts”. Among these there is also Leonardo, with cold gas micropropulsors and the Fine guidance sensor, the ultra-precise stellar compass capable of comparing the light of the faintest stars with a map of over 500,000 stars. The domestic industry has also supplied the subsystems, such as control electronics and data acquisition, in collaboration with the National Institute of Astrophysics and the National Institute of Nuclear Physics. Among the Italian universities involved, in the foreground are the University of Bologna and the Statale of Milan as the scientific guide of the international consortium, Sissa and the University of Genoa. There are over 200 Italian scientists from numerous universities and research institutes.