/cdn.vox-cdn.com/uploads/chorus_asset/file/24769767/1378372150.jpg "Unveiling the Mysteries of Dark Matter and Dark Energy: The Space Telescope Mapping the Entire Universe")
This weekend marked the launch of the European Space Agency (ESA)’s Euclid mission, a space telescope aimed at unraveling the enigmas surrounding dark matter and dark energy. The spacecraft, weighing 2.2 tons and equipped with a 1.2 meter telescope, was propelled into space by a SpaceX Falcon 9 rocket and is currently on its way to orbit around the sun. Originally, the mission was scheduled for launch using a Russian Soyuz rocket from the European spaceport in French Guiana. However, due to Russia’s invasion of Ukraine, cooperation between ESA and Russia ceased. As a result, the telescope was launched from Cape Canaveral Space Force Station in Florida on July 1st at 12:11 AM ET.
The telescope is bound for an orbit known as L2, the second Lagrange point, which is also utilized by the James Webb Space Telescope and other space telescopes. This orbit offers high stability, which is crucial for Euclid’s mission of collecting extremely detailed observations of the universe. The spacecraft is expected to reach L2 within four weeks and undergo two months of preparations before commencing scientific observations around the beginning of October.
Euclid will conduct wide and deep surveys of the universe, piecing together images to generate a map that aids in the understanding of dark matter, constituting approximately 27% of all matter, and dark energy, accounting for about 68% of the universe. The remaining 5% is known as ordinary or baryonic matter, which includes atoms, molecules, and visible matter. Dark matter and dark energy are challenging to study since dark matter does not interact with light, and dark energy remains an unidentified form of energy. Therefore, to gather evidence of these phenomena, observations must be conducted on a large scale.
Describing the significance of a comprehensive survey, Giuseppe Racca, Euclid Project Manager at ESA, stated, “If you want to do cosmology and observe the cosmos as a whole, you need to take a big survey… And Euclid is specially designed with a very wide angle telescope to cover most of the universe that can be observed in a very short time.”
Euclid will survey 36% of the sky over its six-year mission. To observe such a large area, the telescope has an expansive field of view, approximately 2.5 times the size of the moon. In comparison, the Hubble Space Telescope has a field of view that is only 1/12th the size of the moon. While Hubble can capture highly detailed images of galaxies or nebulae, it would require approximately 1,000 years to survey an area of the sky comparable to Euclid.
The limitations of surveying only slightly over a third of the sky arise from the inability to observe distant galaxies in other portions of the sky obstructed by closer stars and dust in our galaxy. Euclid comprises two instruments: the Visible instrument (VIS), operating in the visible light wavelength, and the Near-Infrared Spectrometer and Photometer (NISP), operating in the near-infrared. Accommodating both these wavelengths enables researchers to observe redshifted galaxies, where the light emitted by these galaxies is shifted toward the red end of the spectrum due to their movement away from Earth. By amalgamating observations from both instruments, Euclid can create a three-dimensional map depicting the distribution of visible matter in the universe.
However, dark matter is not directly visible. Its existence can be inferred by examining the distribution of observable matter. René Laureijs, Euclid Project Scientist, elaborated, stating, “Dark energy and dark matter reveal themselves by the very subtle changes they make to the appearance of objects in the visible universe.” Euclid will primarily employ two methods, weak lensing and galaxy clustering, to study dark matter and dark energy. Using these complementary methods allows researchers to cross-validate results, potentially leading to more precise findings.
Weak lensing refers to the effect of gravity exerted by massive objects, like galaxies or galaxy clusters, warping spacetime and acting as a magnifying glass that alters the light emanating from objects situated behind foreground objects. By measuring the strength of this lensing effect, scientists can calculate the mass of the foreground object and compare it with the mass of visible matter in the foreground galaxy. A significant discrepancy between the calculated and observed masses suggests the presence of substantial amounts of dark matter in the foreground.
Galaxy clustering pertains to the distribution of galaxies across the universe in three dimensions. As the universe expands, galaxies move away from Earth, resulting in redshift. Leveraging a phenomenon called baryon acoustic oscillations, scientists can compare the actual distance to a galaxy with its redshift to determine the rate at which the universe is expanding, a factor directly linked to dark energy.
Combining these methods should enhance cosmologists’ understanding of dark matter and dark energy more than ever before. Euclid is expected to capture approximately 1 million images of 12 billion objects throughout its mission. These endeavors bring us closer to detecting and comprehending these elusive phenomena, shedding light on the composition of the universe surrounding us. According to Laureijs, Euclid is not just a space telescope but rather a “dark energy detector.”