Apr 28, 2009
An international team of astronomers last week detected the most distant gamma-ray burst ever recorded, light that was emitted when the universe was less than 5 percent of its present age.
The burst, called GRB 090423 (after the date it was first seen), appears to signal the death throes of a massive star in the very early universe, just 630 million years after the big bang, according to NASA. (Current estimates peg the universe's age at around 13.7 billion years.)
NASA's Swift satellite picked up the short-lived burst Thursday—gamma-ray bursts usually last just minutes, even seconds—and a suite of follow-up observations of the explosion's afterglow at telescopes around the globe enabled an age estimate.
Feb 24, 2009
Ice cores drilled from the poles have provided valuable historical climate records, as the composition of the ice and the air bubbles trapped therein offers a relatively pristine glimpse of ancient conditions. Now a group of Japanese scientists says that the same technique may yield records of significant astronomical events as well.
In a paper posted recently to arxiv.org, Yuko Motizuki of the RIKEN Nishina Center for Accelerator-Based Science in Wako, Japan, and colleagues present evidence for an Antarctic ice-core record of supernovae, or stellar explosions, a millennium ago. A 400-foot (122-meter) core pulled up in 2001 at Dome Fuji station in East Antarctica shows spikes in the concentration of nitrate ion (NO3–) that coincide with two known supernovae in the 11th century: supernova 1006, named for the year it was observed, and the Crab Nebula supernova of 1054. (Astronomers and astrologers in the Far East and the Middle East were already making detailed records of such events by that time.) Nearby supernovae, the researchers write, shower Earth with gamma rays, which can boost levels of nitrogen oxides in the atmosphere that might be recorded as nitrate spikes in the ice.
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