Researchers have used 140,000 distant quasars to measure the expansion rate of the universe when it was only a quarter of the age it is today.
The team used the quasars to determine the "distribution of intergalactic hydrogen gas," a Sloan Digital Sky Survey news release reported.
The first part of the study compared the distribution of quasars with the distribution of hydrogen gas in order to measure the distance of the universe. The team also looked at patterns in the hydrogen gas in order to determine the distribution of it in the early universe.
The team determined that 10.8 billion years ago the universe expanded at a rate of one percent every 44 million years.
"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," Andreu Font-Ribera, of the Lawrence Berkeley National Laboratory, said in the news release.
"We have measured the expansion rate in the young Universe with an unprecedented precision of [two] percent," team leader Timothée Delubac, of the École Polytechnique Fédérale de Lausanne in Switzerland, said in the news release. "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."
Knowing the expansion rate of the universe could help researchers gain insight into the properties of dark energy.
The team found the expansion rate by measuring baryon acoustic oscillations (BAO), which is a "signature imprinted in the way matter is distributed, resulting from sound waves in the early Universe," the news release reported. This can be determined by looking at objects such as quasars and galaxies.
"Three years ago, BOSS used 14,000 quasars to demonstrate we could make the biggest 3-D maps of the Universe," David Schlegel of the Lawrence Berkeley National Laboratory and principal investigator of BOSS, said in the news release. "Two years ago, with 48,000 quasars, we first detected baryon acoustic oscillations in these maps. Now, with more than 140,000 quasars, we've made extremely precise measures of BAO."
When light from these quasars passes through hydrogen gas clouds, the densest objects tend to absorb the most light. As the universe expands the quasar spectrum is stretched out, causing each patch to leave its absorption mark at a different wavelength of neutral hydrogen.
The astronomers measured "from the quasar spectrum how much the Universe has expanded since the light passed through each patch of hydrogen," the news release reported.
"Some of us were afraid it wouldn't work. We were wrong. Our precision measurements are even better than we optimistically hoped for," Schlegel said
