Solar System 7 light-years away. Compared to many other planetary systems, the Solar System stands out in lacking planets interior to the orbit of Mercury. The known Solar System also lacks super-Earths (Planet Nine could be a super-Earth beyond the known Solar System). Uncommonly, it has only small rocky planets and large gas giants; elsewhere planets of intermediate size are typical—both rocky and gas—so there is no "gap" as seen between the size of Earth and of Neptune (with a radius 3.8 times as large). Also, these super-Earths have closer orbits than Mercury. This led to hypothesis that all planetary systems start
Max Planck Institute for Solar System Research Research offers the PhD programme "International Max-Planck Research School (IMPRS) for Solar System Science" together with the University of Göttingen. The Solar System School offers a three-year course of study emphasizing actual research. The curriculum covers the entire area of the solar system from small bodies to the planets and the Sun. The goal is a broad, interdisciplinary, and solid scientific education, extended with courses in numerical physics, space technology, project management, scientific writing, and presentation techniques. There are always about 50 graduate students studying at the Solar System School. Two thirds are from abroad from over 30 different countries.