Enigmatic cosmic source pumps out multiple radio bursts

In 2007 Duncan Lorimer and colleagues scoured archival data from a 2000–01 survey of the Magellanic Clouds and discovered an energetic radio pulse of less than 5 ms duration. Since that discovery, about 20 more so-called fast radio bursts (FRBs) have been reported. One of them, identified in 2014, has now been shown to have a property that sets it apart from all its brethren: It bursts repeatedly. Laura Spitler of the Max Planck Institute for Radio Astronomy and company spotted the source, named FRB121102 (because its first burst was on 2 November 2012), in data taken with the Arecibo Observatory’s William E. Gordon Telescope, pictured here. In May and June 2015, the Gordon telescope pointed to the location of FRB121102 for follow-up observations. Spitler and colleagues discovered 10 additional bursts, whose separations ranged from 23 s to 572 s.

Astronomers are puzzling over the nature of FRB emitters. Before the Spitler and company finding, FRBs appeared to be one-time occurrences whose proposed causes have included the merging of neutron stars and the collapse of a neutron star to a black hole. But those cataclysms are incompatible with a repeating source such as FRB121102. Instead, the researchers suggest, the repeating bursts could be rare, energetic pulses from an extragalactic neutron star. Possibly, many or all FRBs are repeaters whose multiple pulses have escaped detection. Or the lesson of FRB121102 may be that FRBs come in at least two types, as do now-familiar gamma-ray bursts and supernovae. (L. G. Spitler et al., Nature 531, 202, 2016, doi:10.1038/nature17168 . Photo courtesy of the NAIC–Arecibo Observatory, a facility of NSF.)