Planets: One in every 50 worlds may have been stolen from other stars

Planets can be snatched from one solar system by another in the early lives of stars born in dense clusters of dust and gas

By Jonathan O’Callaghan

Approximately one in every 50 planets may have been stolen from other stars in their infancy – perhaps even in our own solar system.

We’ve thought for some time that planets in extremely wide orbits around stars may have been born elsewhere, because it is difficult to form planets at such distances from a star. The hypothesised Planet Nine in our solar system, for example, may be a stolen exoplanet snatched from a passing star.

Such events may occur early in the lives of stars when …