AUSTIN, Texas, Jan. 9 (UPI) -- U.S. astronomers detected a cosmic explosion that took place 7.4 billion years ago -- making it the oldest known short gamma-ray burst.

The explosion was discovered using NASA's Swift satellite and the Gemini Observatory, astronomers said Wednesday in a release.

"This discovery dramatically moves back the time at which we know short GRBs were exploding. The short burst is almost twice as far as the previous confirmed record holder," John Graham of The Johns Hopkins University said in a statement.

The discovery was presented this week at American Astronomical Society's 2008 winter meeting in Austin, Texas.

The astronomers said GRBs are among the most powerful explosions in the universe, releasing enormous amounts of energy in the form of X-rays and gamma rays. The report said a popular model suggests that most short GRBs occur when two neutron stars smash into each other and collapse into a black hole, ejecting energy in two counter-flowing beams.