2024-04-14 07:00:23
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The study of dark energy has always been at the heart of modern cosmology, as it constitutes one of the most intriguing enigmas of our Universe. Recently, a revolutionary study conducted by the Dark Energy Spectroscopic Instrument (DESI) has shed new light on this mysterious force, challenging our established theories about the expansion of the Universe. Using an innovative approach and cutting-edge technologies, DESI has created the largest 3D map of the Universe ever made.
Unprecedented cosmic cartography
DESI is a mountaintop telescope in Arizona that collects light from galaxies as distant as 11 billion light years using an innovative network of 5,000 small robots inside the telescope. Today, scientists are able to go back to the earliest stages of the Universe and follow its evolution until today.
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The study of the impact of dark energy, the enigmatic factor responsible for accelerating the expansion of the Universe, is at the heart of this achievement. The largest 3D map of the cosmos to date was created using DESI data to achieve this goal. With an inaccuracy of less than 1% in measuring the expansion history of the early Universe, it is also the most precise.
Measuring the first moments of the Universe is a huge problem. However, compared to its predecessor, BOSS/eBOSS of the Sloan Digital Sky Survey, which took over a decade to produce results comparable to these, DESI has doubled its effectiveness in mapping the expansion history of these early eras in just one year.
Study of dark energy
Records of baryon acoustic oscillations (BAO), which are residues of pressure waves present in the early Universe, serve as a cosmic standard for researchers. By assessing the apparent size of these waves, they can determine how far away the material is that produced this pattern. This allows them to calculate the rate of expansion of the Universe throughout its history as well as the impact of dark energy on this expansion.
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When the light from ordinary galaxies becomes too faint to be seen beyond a certain distance, scientists turn to quasars. Researchers can map pockets of dense matter by mapping the light emitted by these quasars, which is absorbed as it passes through clouds of intergalactic gas. They apply a technique called “Lyman-alpha forest” to exploit this information in the same way as for galaxies.
The researchers extended their BAO findings back up to 11 billion years using the largest dataset ever collected for Lyman-alpha forest observations, which included 450,000 quasars. After gathering their data, the scientists found that the expansion of the cosmos is not well explained by the standard hypothesis of constant dark energy. The unexpected proximity of galaxies from the three most recent epochs suggests that dark energy may vary over time.
Questioning cosmological models
One of the most striking discoveries is the questioning of existing cosmological models, in particular the Lambda Cold Dark Matter Model (Lambda CDM). The Universe expands at different speeds depending on these factors: dark energy speeds up the expansion of the Universe, while matter and dark matter slow it down.
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Nevertheless, the astronomers discovered some small differences with the Lambda CDM predictions when they combined the first year of DESI data with information from other research. As a result, the basic assumptions underlying our knowledge of the composition and expansion of the Universe may need to be revised.
DESI results have profound implications for our understanding of the Universe. This questioning of the Lambda CDM model suggests that dark energy could evolve over time. This concept could completely change our understanding of cosmology.
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