Pulsars are among the most remarkable and exotic objects in the heavens: rapidly spinning neutron stars with a mass similar to the Sun’s, diameters of only a few tens of kilometers and magnetic fields a million million times stronger than the field we experience at the surface of the Earth. Pulsars emit beams of radio waves from their magnetic poles, which sweep across the Earth as the pulsars spin; these periodic pulses can be detected by Earth-based telescopes. On August 24 2001, during a search for pulsars in nearby galaxies, a telescope at the Parkes Observatory in Australia recorded a brief but unusually strong burst of radio emission. This event lay undetected in the archives of that search for more than half a decade, until it was found by David Narkevic, a student working with Duncan Lorimer and Maura McLaughlin at West Virginia University on a search for single pulses from pulsars with strongly variable radio emission. The arrival time of the burst was dispersed, that is, it changed with frequency, a characteristic of astrophysical signals such as those from pulsars that have propagated through the plasma of ionized gas that fills much of our Milky Way and other galaxies. However, the dependence of arrival time on frequency was far larger than for any known pulsar. Lorimer, McLaughlin, Bailes and their collaborators recognized that this dependence implied that the mysterious source – now known as the “Lorimer burst” – lay far outside our own Milky Way, roughly 100,000 times further than the typical pulsar and so far away that the burst was emitted over a billion years ago. They also showed that despite this enormous distance and the correspondingly huge energy requirements, the object emitting the burst had to be very small – the finite speed of light and the short duration of the signal implied that the burst must have come from a region smaller than the Earth.