EUCLID mission and the study of the dark universe

New EUCLID space telescope from ESA will investigate the dark universe for years to search for evidence of dark matter and dark energy

A new space telescope was launched from the Cape Canaveral Space Force Station in Florida on July 1 at 15:11 GMT. Named EUCLID, it will aid astronomical research in unraveling one of the mysteries of the cosmos: the dark universe. Its main mission is to map the extent and influence of the dark universe with greater clarity than ever before. How did the universe grow in its early days? How do galaxies come together, and why is the expansion of the universe accelerating?

Mystery of the Universe

We have a problem with understanding the universe. It doesn’t make sense if we consider only the visible, measurable, or detectable matter and energy. Einstein‘s famous general theory of relativity, which describes the physical “rules” of the cosmos, would only hold true on cosmic scales if there were five times more dispersed matter in the universe than what exists.

Dark matter, along with another invisible entity, dark energy, is the biggest mystery of cosmology. While dark matter binds things together through gravity, dark energy seems to do the opposite. Discovered for the first time in 1998, it appears to be driving the expansion of the cosmos. Together, dark energy and dark matter constitute 95% of the universe, and we know very little about them.

“Gravity works the same way on both normal and dark matter. But dark matter doesn’t interact with light or anything else, so we know it’s there only from the effect it has on the movements of galaxies and stars” said Isobel Hook, a professor of astrophysics and a scientist of EUCLID. “We discovered dark energy when we observed that the expansion of the universe is accelerating. It doesn’t make sense if you think there’s only gravity”.

Importance of EUCLID

Hook was part of the team that discovered this mysterious acceleration. The chief investigator of that research, American astronomer Saul Perlmutter, was awarded the Nobel Prize in Physics in 2011. Since then, Hook has hoped to uncover what that invisible “thing” separating the universe actually is.

The new European telescope, EUCLID, equipped with a 1.2-meter telescope, will also help map the distribution of dark matter in spacetime in three dimensions for the first time ever. But how exactly will EUCLID unveil the mysteries of the dark universe? The telescope, equipped with sensors capable of detecting visible and infrared light, will join the famous James Webb telescope at the second Lagrange point, P2.

At 1.5 million kilometers from Earth, the gravitational forces of the planet and the Sun are equal, keeping the spacecraft in a stable position relative to Earth. From this point, EUCLID will peer into the depths of the cosmos, 10 billion years back in time, to map the distribution of galaxies. It will take over six years for the $660 million telescope to complete its survey.

3D Map of Dark Matter

EUCLID’s images will closely resemble the famous Deep Field images captured by the Hubble Space Telescope. This will allow astronomers to study how the gravity of dark matter alters the shapes of galaxies in those images. “If you have a very massive cluster of anything, any type of matter, not necessarily dark matter, it will bend light” explained Hook. “Which means anything behind that type of matter will appear distorted”.

These distortions, known as gravitational lensing, are so tiny that they cannot be accurately measured by ground-based telescopes. “The effect is very small, less than 1%” said Giuseppe Racca, the head of the EUCLID project at the European Space Agency (ESA). “Detecting this tiny effect is very challenging. We have to be very precise with the image quality and measure many galaxies to deduce anything”.

Using intricate algorithms, astronomers will be able to use gravitational lensing measurements to calculate the amount of dark matter. This way, they will create the first 3D map of the distribution of dark matter in the universe.

Existence of Dark Energy

The existence of dark energy, on the other hand, is less certain, and it is in this area that EUCLID scientists expect the greatest surprises. The stakes are the definitive validation of Einstein’s theory of relativity, which purports to capture the universal rules of behavior for all matter and energy in the cosmos.

“It might simply be that general relativity doesn’t really work on cosmic scales. So dark energy is not necessary” said Racca. “We need dark energy now if we assume general relativity works. Dark energy is not needed to grow cosmic structures, to grow stars and galaxies”. Many experiments and observations made at smaller distances have confirmed general relativity over the years. If EUCLID’s measurements were to challenge this theory, it would be an absolute breakthrough.

They are searching for dark energy in the distribution of galaxies and galaxy clusters in spacetime. They believe that this distribution is not random but a reflection of microwaves that bounced around the ancient universe about 3 billion years after the Big Bang. “In the cosmic microwave background, we can see this pattern as it looked in the very early times” said Hook.

By comparing the ancient imprints with more recent ones, scientists will be able to see how much the universe has expanded since its early days and what role dark energy might have played in this process. “Since dark energy is pushing the universe apart, if there is a lot of dark energy, we will see that the scale is much larger than we would otherwise expect”. It may take years before astronomical sciences can use EUCLID telescope data and finally unveil the secrets of the dark universe.

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