Quasars are extremely bright, extremely distant objects. They are the disks of material around supermassive black holes, which heat up and glow as material streams inward toward the event horizon. And now, the Sloan Digital Sky Survey (SDSS) has identified more than 147,000 of these objects in the distant universe to create a first-of-its-kind 3-dimensional map of the early universe that is also the largest such map available to date.
The observations were taken over the course of two years as part of the SDSS Extended Baryon Oscillation Spectroscopic Survey, abbreviated eBOSS, which uses the Sloan Foundation 2.5m Telescope at Apache Point Observatory. eBOSS aims to more accurately measure the expansion history of the universe. The quasars in the study were spotted shining at a time when the universe was between 3 and 7 billion years old.
This new, more complete map of the universe and its expansion history agrees with the standard cosmology astronomers have developed over the past two decades and are currently using today, which includes properties such as Einstein’s general theory of relativity and the existence of dark matter and dark energy.
Studying this time frame is particularly important because it’s the epoch leading up to when the universe’s expansion changed from a decelerating to an accelerating expansion. That happened when the universe was roughly 7.8 billion years old, or about 6 billion years ago. Today, that acceleration continues — in short, objects farther away from us are receding faster, and continue to do so because of a cosmological component called dark energy. Characterizing the exact nature of this transition from a decelerating to accelerating universe can place further constraints on the nature of dark energy, which is the dominant component in our universe at the present time.
In a recent press release, Will Percival, a professor of cosmology at the University of Portsmouth and the eBOSS survey scientist, explains,…