A lighthouse in thick fog: the denser the haze, the blurrier the beam. That's how a neutron star behaves — an ultra-dense nugget the size of a city, whose radiation punches through clouds of interstellar gas. Recently astronomers found an especially moody such lighthouse in a distant galaxy. Its radio signals, traveling to us at the speed of light, change faster than any model predicts. Sometimes a burst splits in two: only 7 milliseconds separate the parts, and the second one arrives sharp, as if the first one cleared the way. Likely, the radiation is so powerful it pushes the gas aside, like a gust of wind scattering fog, leaving a tunnel of transparency. The star itself apparently orbits an ordinary companion and occasionally emits regular pulses — a pulsar, first spotted by Jocelyn Bell Burnell. Its magnetic field twists the radio waves so much that the polarization (the direction of oscillation) dances unpredictably.

Once we understand the mechanics of these lighthouses, we'll be able to use them to probe the invisible gas between galaxies. For now, this object reminds us: even a tiny star, one that could fit within a small city's downtown, can burn brighter than an entire Sun.