The December 2018 Issue of Astronomy Magazine had a short article about the discovery of SIMP J01365663+0933473. This is a massive planet (probably a gas giant like Jupiter) that was too small to become a star. There are a couple of cool things about this planet.
First: It is a rogue planet. That means it doesn't orbit a star. It is floating in
Second: It has a magnetic field that is 4 million times stronger than the one on Earth. The star lights up with spectacular
This rouge planet and its moon (or moons) would provide a cool setting for a hard sci-fi story.