Last updated on April 17, 2014 at 10:42 EDT
History of the Cosmos
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History of the Cosmos

July 11, 2011
This artist's conception illustrates the history of the cosmos, from the big bang and the recombination epoch that created the microwave background, to the formation of galactic superclusters and galaxies themselves. The dramatic flaring at right emphasizes that the universe's expansion currently is speeding up.

Observations by the High-z Supernova (High-Z SN) search team, described by Robert Kirshner, hint that we live in a "stop and go" universe whose expansion slowed under the influence of gravity before accelerating again due to an unexplained dark energy.

The High-Z SN search team is an international group of astronomers interested in using type Ia supernovae to trace the expansion of the universe from the present day to nine billion years in the past. In 1998, the High-Z SN team, along with the Supernova Cosmology Project team, uncovered evidence that the universe is accelerating as it expands. Science magazine listed the discovery as one of the top 10 scientific breakthroughs that year. (Year of image: 2003)