Measuring Universe's Rate of Expansion: SDSS Scientists Make Breakthrough

The universe has been enlarging ever since it originated from the Big Bang 13.8 billion years ago. The expansion has sped up in the last five billion years due to repulsive forces of dark energy, and scientists now hope to study the process better by understanding the nature of this mysterious dark energy.

A new study has recently been done by the Baryon Oscillation Spectroscopic Survey (BOSS) team, which is a part of the Sloan Digital Sky Survey (SDSS). They have measured the expansion of the universe with high precision by combining two different techniques, using quasars and intergalactic hydrogen gas. They looked at 140,000 distant quasars - luminous regions in the center of enormous galaxies - when the universe was just one-quarter of its current age.

"A little over a year ago we tried this for the first time and demonstrated that it really works. Now we're back with twice as much data and with remarkable precision of 2 per cent. We are measuring the expansion of the universe with exquisite detail. Like the rings of a tree trunk that tell is its age, each quasar spectrum becomes an archive of the universe's history," said Matthew Pieri of the Institute of Cosmology and Gravitation at the University of Portsmouth and member of the BOSS team.

"We have measured the expansion rate in the young Universe with an unprecedented precision of [two] percent. 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," team leader Timothée Delubac, of the École Polytechnique Fédérale de Lausanne in Switzerland, said in a news release, according to HNGN. 

The BOSS team's study showed that the universe expanded by one percent every 44 million years, 10.8 billion years ago. Studying the early expansion of the universe provides a crucial standard for evaluating the influence of dark energy in the expansion of the universe in the last five billion years.

"We are measuring the expansion rate better than at any point since the afterglow of the Big Bang, known as the Cosmic Microwave Background (CMB), and that precision is giving us a hint that maybe we aren't getting what we expected and so maybe the universe isn't quite as we had thought," Pieri added.

Photo credit: University of Portsmouth (Edited by Vishnuprasad S Pillai)