On September 4, 2005, NASA Swift satellite detects the gamma-ray burst; At redshift 6.29, the burst is by far the most distant known  (NASA illustration)

Astronomers have detected the most distant explosion ever witnessed in the heavens. It was a flash so powerful that they could observe the faint light as it came in from almost the edge of the known universe. The discovery of this burst opens a new view into the frontiers of space.

The U.S. space agency's Swift satellite was routinely scouring the cosmos for exploding stars on September 4 when it spotted what scientists have since realized is the most distant such burst on record.

In astronomy, distance means time. The further something is away, the longer its light has been traveling to get to us. So the star blast is also the most ancient ever observed.

"It was really exciting news for the Swift team when this Swift data were sent to the ground," said Neil Gehrels, the space agency's chief investigator for the Swift spacecraft. "This is exactly what we had built Swift to detect."

The exploding star the Swift satellite observed was typical of the death of a massive star. These blasts are the most powerful in the universe, sending out 100 million times the energy the Sun does in one year. They are not rare, but occur daily, emitting their light in high energy gamma rays. If you could see gamma rays, the sky would twinkle with such bursts.

As soon as Swift detected the explosion, ground telescopes worldwide were trained on the x-ray and visible light afterglow and confirmed the event.

University of North Carolina astronomer Daniel Reichart measured the non-visible, infrared wavelengths of light from the dying star. His calculations show that the explosion occurred almost 13 billion years ago, close to the time of the cataclysmic explosion believed to have created the universe, the Big Bang.

"This cosmic explosion occurred nearly 900 million years after the Big Bang," he said. "That may sound like a long time, but the universe is 13.7 billion years old, which means that this star exploded when the universe was six to seven percent of its current age."

The observance sets a new record for the distance and age of an observed star explosion. The next oldest exploding star ever witnessed took place 500 million years later.

However, the blast is important not for the superlatives that can describe it, but for what it can tell astronomers about the cosmos.

"This is what we've all been waiting and hoping for," said University of Chicago astronomer Donald Lamb, who says the discovery provides a new tool to study the infant universe. "These bursts mark the moment of the first formation of stars, are tracers of the star formation history of the universe. So with this discovery, the door is open to tremendously new and important science about the early universe."

The finding comes less than a decade after scientists first learned that the gamma rays the exploding stars emit were coming from beyond our galaxy. In fact, it was only three years ago that astronomers determined what causes them. The Swift spacecraft was launched last November to cast a full time eye on them.

Donald Lamb predicts that astronomers will now begin finding even older, more distant star explosions to see even closer to the time the universe first lit up, thought to be about 600 million years after the Big Bang.