Spiral Arm Motion Solves Exoplanet Formation Mystery

There are plenty of exoplanets scattered throughout the galaxy, so it would stand to reason there are also plenty of stars that are in the process of forming new exoplanets. Tracking down stars that are in different stages of that process can shed light on the exoplanet formation process, and potentially even on how planets in our own solar system developed. But determining what star systems are going through that process, let alone where they are in the process itself, can be tricky. A new paper in Nature Astronomy from Tomohiro Yoshida and his co-authors at the National Astronomical Observatory of Japan and several other Japanese and American research institutions, seems to have found one that finally answers a mystery that has stood in planetary formation theory for decades – how do gas giant exoplanets form so far away from their stars?