BOSS project looks at acceleration rate before dark energy hit the gas
New measurements have captured the universe’s expansion when it was slowing down 11 billion years ago, before a mysterious entity called dark energy took over and began spurring the cosmos to expand faster and faster. The measurements, reported online November 12 at arXiv.org, are an important step toward understanding what dark energy is and how it works.
About 15 years ago, astronomers discovered that the universe’s expansion is accelerating by cataloging spectacular stellar explosions called type 1a supernovas. Because each explosion emits almost exactly the same amount of light, astronomers can use a supernova’s observed brightness to determine its distance, and then measure its redshift, or how much its light is stretched, to determine how fast the supernova is moving away from Earth. Astronomers Adam Riess of Johns Hopkins University, Saul Perlmutter of the University of California, Berkeley and Brian Schmidt of Australian National University shared