Dark energy

Blogs about dark energy

Deep field image (Image Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA Acknowledgments: T.A. Rector (University of Alaska Anchorage/NSF’s NOIRLab), M. Zamani (NSF’s NOIRLab) & D. de Martin (NSF’s NOIRLab))

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29 articles report various aspects of the results of a major cosmological research on the largest sample of galaxies – 226 million of them – ever observed to produce the most accurate measurements of the composition and growth of the universe. More than 400 scientists from the DES (Dark Energy Survey) Collaboration used images captured by the Dark Energy Camera in the first three years of the program, which started in 2013, to obtain results. The goal is to improve our knowledge of the universe, in particular, the nature of dark matter and dark energy.

The extent of the expansion of the universe is increasingly precise and stresses the discrepancy between the measurements

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An article published in “The Astrophysical Journal” reports a new measurement of the expansion of the universe, which is approximately 9% faster than the estimates made by studying the early universe. A team of astronomers led by Nobel laureate Adam Riess combined observations made with the Hubble Space Telescope of 70 variable stars called Cepheid variables used for measurements with others conducted by the Araucaria project to obtain extremely precise measurements of their brightness. The discrepancy between the measurements of the expansion of the near universe and those of the early universe remains and it’s important to improve the measurements to obtain clues to the origin of the discrepancy.

A measurement of the Hubble constant based on quasars suggests possible changes to cosmological models

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An article published in the journal “Nature Astronomy” describes the use of quasars as cosmic tracers to measure the expansion of the universe up to 12 billion years ago. Guido Risaliti of the University of Florence and Elisabeta Lusso of Durham University studied the X-ray and optical emissions of a number of quasars using the comparison between those emissions to accurately assess their distances. The results could explain the discrepancies between the different measurements carried out with other methods suggesting that the density of the mysterious dark energy isn’t constant over time.

Artist's concept of the universe on a 5D bubble (Image courtesy Suvendu Giri)

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An article published in the journal “Physical Review Letters” describes a new model of the universe that proposes that it exists on the edge of an expanding bubble in a five-dimension space-time. A team of researchers from the Swedish University of Uppsala used string theory to hypothesize that the matter existing in the universe is accomodated at the edges of strings that extend into the fifth dimension. According to this hypothesis, what is called dark energy is an effect described by a cosmological constant in the four-dimension Friedmann equations.

CMB Final Map (Image ESA/Planck Collaboration)

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ESA presented the final map of the cosmic microwave background radiation created thanks to the Planck Surveyor space probe. This map shows what the universe was like before galaxies formed when it was about 380,000 years old. These are the results of the last processing of the collected data and now scientists are certain that the temperature and polarization are accurately determined. This final map confirms the standard model but also the inconsistency between the calculation of the Hubble constant based on those data and the one based on observation of the current universe.