At 3:55 a.m. EDT on April 23, 2009, the Swift satellite detected a ten-second-long burst of gamma rays from so far away that it is the youngest object in the Universe ever seen.
Gamma-Ray Burst 090423
The gamma-ray burst, named GRB 090423, after the date it was discovered, is the new record holder for most distant and youngest object seen in the Universe. It released its energy when the Universe was just 640 million years old, or about 13 billion years ago.
"With a redshift of 8.2, this is the most remote gamma-ray burst ever detected, and also the most distant object ever discovered," says Nial Tanvir of the University of Leicester, in a press release sent to the American Astronomical Society. The previous record holder had a redshift of 6.7, which is 180 million light-years closer than GRB 090423.
Gamma-Ray Bursts Explained
Gamma-ray bursts, the brightest explosions in the cosmos, occur when massive stars reach the end of their lives and collapse into black holes or neutron stars. Gas jets from these collapses shoot outward into space and strike gas that had been previously cast off by the star. This gas heats and produces the afterglow seen by telescopes such as Swift.
"The burst most likely arose from the explosion of a massive star," Derek Fox at Penn State University explains about GRB 090423. "We're seeing the demise of a star – and probably the birth of a black hole – in one of the Universe's earliest stellar generations."
"Burst afterglows provide us with the most information about the exploded star and its environs," says Tanvir. "But we have to target afterglows quickly because they fade out so fast."
Tracking Gamma-Ray Bursts
As soon as Swift detected the gamma-ray burst, other telescopes around the world turned to the same point in the constellation Leo to record the event. The telescopes saw a fading afterglow in x-rays but no record of the event in visible light.
"That alone suggested this was a very distant object," Fox explains. "If you look far enough away, you can't see visible light from any object." As optical emissions travel across vast distances in the Universe, they are shifted into longer wavelengths, creating what is know as the redshift.
Using the Gamma-Ray Burst Discovery in Science
"At its most basic level, this discovery tells us that there were massive stars at this moment in cosmic history, but equally important we can use events like this to probe how the Universe evolves when it is less than five percent of its current age," says Andrew Levan of the University of Warwick.
"This discovery proves the importance of gamma-ray bursts in probing the most distant parts of the Universe," says Tanvir. "We can now be confident that even more remote bursts will be found in the future, which will open a window to studying the very first stars and the ultimate end of the Dark Age of the Universe."
Sources: Science and Technology Facilities Council and European Southern Observatory
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