WORLDS WITHOUT SUNS

When we think about planets, a star usually comes as part of the package. After all, where would Earth be without the Sun? Imagine Luke Skywalker’s home planet of Tatooine without its twin suns, or Superman without Rao, the red supergiant around which Krypton spun. Yet you’d be wrong to imagine that planets are never starless. Astronomers have already found swarms of rogue planets – worlds wandering the open chasm of space alone.

As far as we know, planets always start off with stars. They are the leftover fragments from star formation, the offcuts that you’d throw away in a skip if you were building a house. A cloud of gas and dust that was otherwise minding its own business may begin to contract if it’s hit by a shock wave from an exploding star. As the cloud compresses, gravity takes over and bundles it into an ever-smaller space until fledgling