The Sloan Digital Sky Survey (SDSS) has published a comprehensive analysis of the largest three-dimensional map of the Universe, revealing that six billion years ago, the expansion of the Universe began to accelerate.
Over 100 astrophysicists collaborated in the extended Baryon Oscillation Spectroscopic Survey (eBOSS). The purpose of eBOSS was to create detailed measurements of more than two million galaxies and quasars, covering 11 billion years of cosmic time.
20 years of observations from eBOSS have been published by past and present members of the University of Portsmouth’s Institute of Cosmology and Gravitation (ICG). Dr Julian Bautista, a research fellow at the ICG and the lead data scientist for eBOSS, said: “Thanks to these maps, my colleagues and I were able to observe and study how fast the Universe was expanding and how fast structures formed.”
Professor Kyle Dawson, of the University of Utah, led the team announcing today’s results. He said: “We know both the ancient history of the Universe and its recent expansion history fairly well, but there’s a troublesome gap in the middle 11 billion years. For five years, we have worked to fill in that gap, and we are using that information to provide some of the most substantial advances in cosmology in the last decade.”
Mapping the Universe
Astronomers know what the Universe looked like in its infancy, they also know its expansion history, but no one has ever created such an extensive catalogue of the universe.
This new map reveals the filaments and voids that define the structure of the Universe, starting from the time when the Universe was only about 300,000 years old. The cosmic history revealed in this map shows that about six billion years ago, the expansion of the Universe began to accelerate, and has continued to get faster and faster ever since.
Dr Bautista said: “We think this acceleration is due to an invisible component of the Universe we call ‘dark energy’, but we don’t understand well how dark energy behaves. It could just be a cosmological constant as suggested by Einstein, but that is extremely difficult to reconcile with theories of particle physics.
“Before eBOSS, it was as if we had this movie of the Universe but with most of it missing. We had some images of the beginning and we could see how the story ends, but now, thanks to eBOSS, we can finally see most of the Universe’s tale and how dark energy was one of the main actors in it.”