The most powerful explosions in the universe since the big bang could help astronomers find billions of as-yet-undetected stars. A new report from researchers in England and California suggests that gamma-ray bursts--which release as much energy in a few seconds as the sun does in its entire lifetime--could illuminate hard-to-see, dust-enshrouded galaxies where much of the star formation in the cosmos has taken place. As much as 80 percent of stars may be forming in these mysterious locales, says Andrew Blain, an astronomer at the California Institute of Technology. "In these galaxies, 99 percent of the energy produced by these stars is obscured by dust," he explains.
If most stars form in these dim galaxies, it stands to reason that the majority of gamma-ray bursts occur there too, throwing light, however briefly, on their elusive neighbors. So far, Edo Berger, also at Caltech, and his collaborators have used this method to spot one galaxy so faint that only conventional approaches devoted to the most concentrated searches could have found it otherwise. Although it strains current technology, the new technique could in theory find more such galaxies than can standard, less-directed methods, Blain and his colleagues note in their report, which will appear in a forthcoming issue of the Monthly Notices of the Royal Astronomical Society.
A separate England-based team, led by astronomer Nial Tanvir of the University of Hertfordshire, has looked in the vicinity of four candidate gamma-ray bursts over the past year for glowing dust. Although it hasn't found any yet, the group posits that another six to 10 attempts should yield better results. If not, that could itself be an interesting result: it might indicate that dust-covered galaxies are either powered by the gravitational energy of matter falling into giant black holes or are somehow not conducive to hosting these mighty explosions.
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"Gamma-ray bursts are the most luminous objects in the universe, and this paper highlights how they might reveal new classes of galaxy," comments Martin Rees, astronomer royal of Great Britain and a theoretical astrophysicist at Cambridge University. "This is important not only for our understanding of galaxies but also because it will help to solve the mystery of what triggers the gamma-ray bursts themselves."
