Image Credit: ESA/ATG medialab (spacecraft); NASA, ESA, CXC, C. Ma, H. Ebeling and E. Barrett (University of Hawaii/IfA), et al. and STScI (background)

Dark matter isn't just that mysterious cosmic thing that creates metahumans in Flash World from DC. It is also a subject of ESA's mission Euclid, planned to be launched in 2022.

Up to today, a lot is unknown about the ''dark side'' of the universe, and until about 30 years ago, scientists believed that the universe was only composed of subatomic particles like protons, neutrons and electrons; in other words, ordinary matter. However, now it is assumed that ordinary matter is only 5% of the universe's energy density, and the predominant components are dark energy (69%) and dark matter (26%).

Dark energy is causing an acceleration of the universe's expansion. However, the current knowledge in fundamental physics can't explain this energy scale or existence. The nature of dark matter is also unknown, yet, it is believed that, like ordinary matter, dark matter exerts gravitational attraction, but without emitting light. In an attempt to understand the nature of dark matter, scientists make predictions using supersymmetric extensions of the standard model of particle physics. However, to explain the cold and hot dark matter components, there is a possibility that we need to revise our understanding of gravity on cosmological scales. Those components can't be seen but detected by the movement, shape, and distribution of galaxies, and by the rate of universe expansion.

ESA/XMM-Newton (X-rays); CFHT-LS (optical); XXL Survey

Euclid mission will map the geometry of the dark universe, investigating the evolution of cosmic structures and the relationship between distance and redshift. Mapping shapes, positions, and movements of the galaxies across the entire extragalactic sky, and its large-scale structures.

Redshift is the wavelength in which the light is stretched, as light ''shifts'' towards the red part of the spectrum. It is somehow similar to the Doppler effect of sound waves frequency when a source of sound moves relative to an observer, as an example, the audible pitch change of an ambulance siren from a high frequency when moving closer, to a low frequency when getting distant from an observer. Light behaves like a wave, experiencing a similar effect. As it is known, other galaxies are moving away from us; their lights are shifting to a longer wavelength (a redder part of the spectrum). However, as light travel at high speed, we do not see this effect. Though the redshifts observed in distant objects are due to the expansion of the universe, not from a Doppler phenomenon, as two objects can be stationary in space and still experience redshift when space itself is expanding.

Structural and thermal model of the Euclid satellite - Image Credits: ESA–S. Corvaja

Euclid is a combined mission which will simultaneously measure weak gravitational lensing (WL) and baryonic acoustic oscillations (BAOs). ''WL is a method to map the dark matter and measure dark energy, which measures mass inhomogeneities along the line-of-sight (distortions of galaxy images). While BAOs are wiggle patterns of a group of galaxies, they provide a standard ruler to measure dark energy and the universe expansion.'' These techniques give a measurement of large-scale structures via different physical fields such as potential, density, and velocity.

For that, the Euclid spacecraft will be able to perform corrective actions in case of anomalies, and the ground segment won't need to monitor the spacecraft in real-time. Either antenna in the ground station in Cebreros, Spain, or the one in Malargue, Argentina will be used for all communications with Euclid. The Mission Operations Centre (MOC) is responsible for the ground segment and operations infrastructure for the flight operations segment. And it will be set up at ESA's European Space Operations Centre (ESOC) in Darmstadt, Germany, customizing the existing infrastructure to meet the specific requirements of this mission. The MOC will deliver the raw scientific data to the Science Ground Segment.

Therefore, ESA's Euclid mission will help understand crucial questions of fundamental physics by investigating the properties of dark energy while measuring the acceleration and its variation in different ages of the universe. As well as the nature of dark matter by mapping it is distribution. The mission will also challenge our understanding of the cosmological model, and the beginning of our universe, as well as Einstein gravity theory and general relativity on cosmic scales.

Information used to write this post was extracted from ESA's webpage about the Euclid mission.

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This article was written by Juliane Verissímo - Marketing Department of VisionSpace

The Dark Side of the Universe