A planet orbits a pair of stellar corpses – a white dwarf and a pulsar called PSR B1620-26 (circled) – in an ancient globular star cluster called M4. A new study argues that pairs of stars – in which one or both have died – might be good places to find planets (Image: NASA/H. Richer/University of British Columbia)

WE THINK of stars as having just one shot at forging planets – a narrow window when the infant stars are surrounded by a disc of dust and gas. Now it seems paired stars may regularly spawn two or even three generations of planets.

The mechanism for …