Lifting the fog on "dark" gamma-ray bursts

BERKELEY — Gamma-ray bursts, with their ability to pierce through gas and dust to shine brightly across the universe, are revealing areas of intense star formation and stellar death where astronomers have been unable to look - the dusty corners of otherwise dust-free galaxies. Artist's illustration of a gamma-ray burst occurring in a dusty region of intense star formation. If a dust cloud lies between the burst and Earth, the optical light will be almost entirely absorbed, but the gamma-rays and X-rays will easily penetrate the dust. New evidence suggests that most "dark" gamma-ray bursts — those without optical afterglows — form in similar dusty environments. (Aurore Simonnet/Sonoma State University, NASA Education & Public Outreach) The conclusion comes from a survey of "dark" gamma-ray bursts — bright in gamma- and X-ray emissions, but with little or no visible light — reported today (Monday, June 8) at a meeting of the American Astronomical Society in Pasadena, Calif., by astronomers from the University of California, Berkeley, and institutions around the world. "Our study provides compelling evidence that a large fraction of star formation in the universe is hidden by dust in galaxies that do not appear otherwise dusty," said Joshua Bloom, associate professor of astronomy at UC Berkeley and senior author of the study. Star formation occurs in dense clouds that quickly fill with dust as the most massive stars rapidly age and explode, spewing newly created elements into the interstellar medium to seed new star formation.