Lorimer Burst
A five-millisecond spike hidden in old Parkes radio-telescope data, recorded on 24 July 2001 and found six years later by David Narkevic while working with Duncan Lorimer, appeared three degrees from the Small Magellanic Cloud with a dispersion too large for an ordinary Milky Way source; follow-up searches found no repeat, early doubts compared it with terrestrial radio interference, yet the signal became FRB 010724, the first recognized fast radio burst, leaving astronomers with a harder question: what kind of cosmic engine can flash with such power once, from far beyond our galaxy, and vanish back into silence?
The Lorimer Burst began as a trace in old radio telescope data, not as a flash anyone watched in real time. On 2001-07-24, the 64-metre Parkes radio telescope in New South Wales, Australia, recorded a brief, extremely bright radio pulse during a survey of the Magellanic Clouds. The signal lasted less than five milliseconds, swept downward through the observing band in the way expected from radio waves delayed by ionized plasma, and appeared near, but not physically inside, the Small Magellanic Cloud. It remained unnoticed until 2007, when David J. Narkevic, working with Duncan R. Lorimer and collaborators, reprocessed archival pulsar survey data and found an event that did not fit any familiar category.
The discovery paper, published electronically through Science Express on 2007-09-27, described a 30-jansky dispersed burst with a dispersion measure of about 375 pc cm-3. The signal was far too dispersed to be easily explained by the Milky Way foreground or by known pulsars in the Magellanic Clouds. The authors argued that the burst was probably extragalactic, possibly hundreds of megaparsecs away, and that similar events might occur across the sky every day. At the time, this was a bold interpretation. A single pulse, found in a single old data set, could be a new cosmic phenomenon, or it could be a misleading instrument effect, software artifact, or local radio-frequency interference.
For several years the case occupied an uncertain border between discovery and anomaly. No immediate repeat bursts were found in follow-up observations, and the event was so bright that some astronomers wondered why no fainter examples had also appeared. The uncertainty deepened when Parkes data produced perytons, swept-frequency terrestrial signals that partly resembled dispersed astrophysical pulses. Those later signals were eventually traced to microwave ovens at the observatory being opened prematurely while the telescope was pointed at susceptible angles. The microwave solution explained the perytons, but it did not explain FRB 010724. The Lorimer Burst differed in beam pattern and other observational details, and the peryton investigation strengthened the distinction between terrestrial mimics and genuine fast radio bursts.
The wider mystery shifted after additional FRBs were reported. The 2013 Thornton et al. Parkes sample helped establish a population, the Arecibo detection of FRB 121102 showed that the phenomenon was not confined to Parkes, and later localization work linked some FRBs to distant host galaxies. Modern reviews treat the cosmological nature of FRBs as well established, although the physical engines behind all FRB sources remain incompletely understood. Magnetars, highly magnetized neutron stars, are now among the leading source classes for at least some FRBs, especially after a Galactic magnetar produced an FRB-like burst in 2020. That does not identify the exact source of the Lorimer Burst, and no host galaxy has been confirmed for it.
For this case file, the event is marked resolved in the limited sense that the once-suspect signal is now accepted as the first recognized member of a genuine astronomical class rather than a known terrestrial interference event. The deeper astrophysical question remains active: what object produced FRB 010724, why it appeared so bright, whether it repeated below detection limits, and how it fits into the expanding family of fast radio bursts.