Keck Study Sheds New Light on "Dark" Gamma-ray Bursts
Since its launch in 2004, NASA's Swift has detected more than 430 gamma-ray bursts. Roughly half of them are "dark" bursts that emit little or no visible light. Dense knots of dust in otherwise normal galaxies dim the light of a dark gamma-ray burst (center). The dust absorbs most or all of a burst's visible light but not higher-energy X-rays and gamma rays. Credit NASA/Swift/Aurore Simonnet Gamma-ray bursts are the universe's biggest explosions, capable of producing so much light that ground-based telescopes easily detect it billions of light-years away. Yet, for more than a decade, astronomers have puzzled over the nature of so-called dark bursts, which produce gamma rays and X-rays but little or no visible light. They make up roughly half of the bursts detected by NASA's Swift satellite since its 2004 launch.