Gamma-ray burst goes the cosmic distance
Astronomers have identified a new record holder for most distant object in the universe — a gamma-ray burst emanating from a region 13.035 billion light-years from Earth.
On April 23, NASA’s Swift satellite discovered the burst — a 10-second flash of highly energetic radiation believed to mark the explosive collapse of a massive star into a black hole. Within three hours of Swift’s detection, astronomers recorded the burst’s infrared afterglow using the U.K. Infra-Red Telescope and the Gemini North Telescope, both on Hawaii’s Mauna Kea. Those observations, reported online (gcn.gsfc.nasa.gov/gcn3_archive.html), suggested that the explosion ignited when the 13.7-billion-year-old universe was only about 630 million years old.
Because of the universe’s expansion, objects farther from Earth recede faster than closer ones, causing the light they emit to appear shifted to redder, or longer, wavelengths. Spectra taken by Nial Tanvir of the University of Leicester in England and his colleagues confirmed that the burst, dubbed GRB 090423, has a record-breaking redshift of 8.2. The previous distance record holder, a remote galaxy, had a redshift of 6.96, indicating that it resides 12.9 billion light-years from Earth.
The burst’s remote location means that the light from its afterglow, which can last for days or months, can be used as a searchlight to probe some of the earliest galaxies in the universe.