Following a complex investigation, researchers in the United States were recently able to produce the most accurate measurements of galaxy distances in the distant Universe. This allowed them to figure out the precise instant when dark energy was activated.
Dark energy is believed to be a pervasive force, making up about three quarters of the universal mass-energy budget, which is responsible for the ever-accelerating expansion of the Cosmos, as well as for determining the large-scale structure of the Universe.
It is now believed that expansion – a phenomenon which began with the Big Bang – started to slow down about 5 to 7 billion years ago, on account of the influence gravity exerted on everything in the Universe. At that precise time, dark energy stepped in, and began accelerating expansion yet again.
Despite these new data, the very nature of dark energy remains a mystery for astrophysicists, who still cannot explain a host of properties that this force should theoretically have. Understanding dark matter and dark energy is key to figuring out how the Universe evolved, and how it now works.
According to scientists at the Harvard-Smithsonian Center for Astrophysics
(CfA), the data used in this new study came from the third Sloan Digital Sky Survey's (SDSS-III) Baryon Oscillation Spectroscopic Survey (BOSS) project.
“We see the influence of dark energy on cosmic structure, but we have no idea what it is. The data gathered by this survey will help answer that question,” CfA expert and SDSS-III director, Daniel Eisenstein, explains.
“There's been a lot of talk about using galaxy maps to find out what's causing accelerating expansion. We've been making a map and now we're using it – starting to push our knowledge out to the distances when dark energy turned on,” adds David Schlegel.
The expert, who is based at the US Department of Energy's (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab), is the principal investigator for the BOSS project. He explains that the only possible explanation for universal expansion is a deviation from the theory of general relativity.
The BOSS-related investigations are conducted using a custom-designed spectrograph on the SDSS 2.5-meter telescope at Apache Point Observatory, in New Mexico. Their purpose is to analyze more than 1 million galaxies within 6 years. Thus far, 250,000 galaxies have already been surveyed.
Ultimately, this research will enable astrophysicists to gain a deeper understanding into how the Universe will come to an end.