A single fast radio burst localized to a massive galaxy at cosmological distance

Pinpointing a single fast radio burst Fast radio bursts (FRBs) are flashes of radio emission from distant astronomical sources. Two FRBs are known to have repeated, but most last just a few milliseconds and are never seen again. Most telescopes that are sensitive to single FRBs have poor angular resolutions, so the FRB host galaxies remain unknown. Bannister et al. used a dedicated observing mode on a radio interferometer to detect and localize the nonrepeating FRB 180924, then followed up with optical telescope observations (see the Perspective by Petroff). They found that the FRB came from a medium-sized galaxy at a cosmological distance. Localizing FRBs will help determine their causes and allow them to be used as cosmological probes. Science, this issue p. 565; see also p. 546 Radio interferometry has been used to detect and localize a single nonrepeating fast radio burst. Fast radio bursts (FRBs) are brief radio emissions from distant astronomical sources. Some are known to repeat, but most are single bursts. Nonrepeating FRB observations have had insufficient positional accuracy to localize them to an individual host galaxy. We report the interferometric localization of the single-pulse FRB 180924 to a position 4 kiloparsecs from the center of a luminous galaxy at redshift 0.3214. The burst has not been observed to repeat. The properties of the burst and its host are markedly different from those of the only other accurately localized FRB source. The integrated electron column density along the line of sight closely matches models of the intergalactic medium, indicating that some FRBs are clean probes of the baryonic component of the cosmic web.