The expansion of the universe has been measured with the greatest precision ever in a new examination of thousands of distant objects.
Using the Baryon Oscillation Spectroscopic Survey (BOSS), astronomers tracked quasars. A pair of these studies from Europe and the United States provides a glimpse into the rate at which the universe has expanded since the Big Bang, about 13.8 billion years ago.
One study used tested techniques and contained more data than ever before -- it was carried out by Timothée Delubac, of the Swiss Federal Institute of Technology in Lausanne and his team. Analysis from this study was combined with another study using a new method. This was directed by physicist Andreu Font-Ribera from Lawrence Berkeley National Laboratory.
BOSS is the main thrust of the third Sloan Digital Sky Survey (SDSS-3). This research measures fluctuations in the density of interstellar gas in the most distant regions of the known observable universe.
Baryon acoustic oscillations (BAO's), like sound waves in interstellar gas created billions of years ago, are analyzed by the system. These waves create distinctive patterns in the gas, which provides astronomers detailed information about matter during the time light filled the universe.
"Three years ago BOSS used 14,000 quasars to demonstrate we could make the biggest 3D maps of the universe. Two years ago, with 48,000 quasars, we first detected baryon acoustic oscillations in these maps. Now, with more than 150,000 quasars, we've made extremely precise measures of BAO," David Schlegel, principal investigator of BOSS at Berkeley Lab, said.
Expansion of the universe has now been calculated at 68 kilometers (42 miles) per second per megaparsec (3.26 million light years). That number is believed to be accurate within 2.2. percent, making it the most accurate measurement ever made of the velocity at which galaxies are flying apart from one another.
BAO's were first formed in the early history of the universe, when the young cosmos was too dense for light to travel freely. Around 380,000 years after the Big Bang, light was first able to travel thorough space freely. The cosmic microwave background radiation preserves a record of the BAO patterns that can still be observed today.
Quasars are young, hot black holes that grow as they pull matter in, creating a great deal of radiation as material spirals in toward the event horizon. Light from the distant quasars is partly absorbed by gas lying between the object and the Earth, leading to the findings. More than140,000 of the objects were examined as part of the studies which led to the measurement.
