The National Aeronautics and Space Administration said the event occurred when the universe was less than 5 percent of its present age and is the most distant cosmic explosion ever seen.

"Swift was designed to catch these very distant bursts," said Swift lead scientist Neil Gehrels at NASA's Goddard Space Flight Center in Greenbelt, Md. "The incredible distance to this burst exceeded our greatest expectations -- it was a true blast from the past."

The 10-second-long gamma-ray burst was detected at 3:55 a.m. EDT Thursday.

Astronomers around the world quickly aimed their telescopes at the event. At the Galileo National Telescope on La Palma in the Canary islands, a team including Guido Chincarini of the University of Milan-Bicocca, Italy, determined the burst occurred more than 13 billion light-years away.

"It's an incredible find," Chincarini said. "What makes it even better is that a telescope named for Galileo made this measurement during the year in which we celebrate the 400th anniversary of Galileo's first astronomical use of the telescope."