Astronomers Measure Early Universe Expansion Rate Using 140,000 Quasars

Astronomers have measured rate of expansion of early Universe using 140,000 distant quasars. According to the research team, the current measurement of expansion is the "best-ever" with a precision of 2 percent.

The research, conducted by astronomers at Sloan Digital Sky Survey, found that some three billion years after the Big Bang (around 10.8 billion years ago), the Universe was expanding at about 1 percent every 44 million years, BBC reports. The research used measurements of both matter and intergalactic gas to estimate the rate at which the Cosmos was pushing itself apart.

Quasars or "quasi-stellar radio sources" are the bright centers of very distant galaxies. Researchers reported using Baryon Oscillation Spectroscopic Survey (BOSS). Scientists at BOSS are trying to solve some of the long-standing mysteries of the Universe such as how are the stars clustered? And what exactly is accelerating the expansion of Universe?

"If we look back to the Universe when galaxies were three times closer together than they are today, we'd see that a pair of galaxies separated by a million light-years would be drifting apart at a speed of 68 kilometers per second as the Universe expands," said Andreu Font-Ribera,(Lawrence Berkeley National Laboratory, according to a news release.

The study results are actually based on two separate analyses. One of the researches, conducted Font-Ribera and colleagues, measured distances in the Universe by comparing the distribution of quasars and hydrogen. The other research by Timothée Delubac (École Polytechnique Fédérale de Lausanne, Switzerland, looked at patterns of hydrogen to estimate the distribution of mass in early Universe.

According to the researchers, measuring the rate of expansion during different epochs in Universe's history could enable scientists to learn more about the mysterious "dark energy."

"By probing the Universe when it was only a quarter of its present age, BOSS has placed a key anchor to compare to more recent expansion measurements as dark energy has taken hold," said Delubac.

Ancient Echo and Dark Energy

In both the studies, baryon acoustic oscillations (BAOs) were used to calculate the rate at which the Cosmos was pushing apart. According to SDSS-III, BAOs are sound waves that spread during the early Universe. These waves are now imprinted on the cosmic microwave background fluctuations.

The evolution of Universe has been divided into several epochs. Other researchers consider BAOs to be ancient relics from the pre-decoupling Universe. BAOs can be used as standard rulers to measure the evolution of Universe's structure and compare the expansion rates during different eras of Cosmic evolution.

The new data on the rate of early Universe expansion is expected to help astronomers understand the nature of the dark energy.

The research was presented at the April 2014 meeting of the American Physical Society in Savannah, GA.

BOSS was in news in January for its measurement of the Universe using BAOs. The accuracy of the measurement was about one percent, researchers said.