Biggest discovery in cosmology for 26 years? – Dark energy not constant
The detailed analysis of a huge map of the sky also confirms Einstein's findings. But there is growing evidence that dark energy is not constant.
Das DESI ist am Kitt Peak National Observatory installiert.
(Image: KPNO/NOIRLab/NSF/AURA/R.T. Sparks)
A much more extensive analysis of the data collected in the first year after the Dark Energy Spectroscopic Instrument (DESI) was commissioned also suggests that the mysterious dark energy is changing. At the same time, the analysis has provided further confirmation of our standard model of gravity and of Albert Einstein's theory of relativity. This has now been announced by the researchers involved in the study, which also places tighter limits on possible alternative theories. Overall, this is one of the most thorough tests to date of the general theory of relativity and the behavior of gravity on a cosmic scale.
Help for neutrino research
The team of more than 900 people from 70 research institutions has also determined a new upper limit for the mass of neutrinos. After earlier investigations had already determined a lower limit of at least 0.059 eV/c², a maximum value of at most 0.071 eV/c² has now been arrived at on the basis of the influence of the ghost particles on structure formation. The actual mass must lie within this narrow window. This and the other results are presented in several research articles, which can be viewed online.
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As the group now explains, the detailed analysis is once again about the distribution of galaxies and matter in the universe over a period of 11 billion years. Almost six million galaxies were measured for this purpose. According to astrophysicist Mustapha Ishak-Boushaki, one of the leaders of the study, the resulting evidence that dark energy is dynamic and not constant is the most important discovery in the study of the universe since the detection of accelerating expansion. His team is currently working on analyzing the data collected over three years. It could become clear as early as the spring whether the evidence is becoming more conclusive.
Most comprehensive map of the cosmos
The DESI has been collecting spectra of millions of galaxies since 2021, covering around a third of the night sky. From the spectra, researchers can not only deduce the chemical composition of the emitting objects, but also their relative distance and proper motion, depending on how far they are shifted into the red. The aim is to create the most comprehensive map of the expanding universe. Thanks to robot-controlled glass fibers, the instrument can simultaneously capture the spectra of 5,000 galaxies and measure up to 150,000 objects on a good night.
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After Edwin Hubble and others proved at the beginning of the 20th century that the universe was expanding, researchers had long assumed that this expansion was slowing down. It was not until 1998 that the analysis of distant supernovae revealed that, on the contrary, the expansion was actually accelerating. Saul Perlmutter, Brian Schmidt and Adam Riess were awarded the Nobel Prize in Physics for this discovery in 2011. This acceleration is thought to be caused by so-called dark energy, the nature of which remains a mystery. The DESI is intended to help explain it and the analysis now confirms the impression that this can be achieved.
(mho)
