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
Outer Planet Flagship Mission Outer Planet Flagship Mission The Outer Planet Flagship Mission is a type of NASA program to research larger size missions to the outer solar system, and some examples of this type of mission are Galileo or Cassini-Huygens. In 2013 after encounter some technical issues and funding in the early 2010s, development was paused although overall research continued. One issue is the other big NASA missions such as in astrophysics and another is availability of RTG's One proposal was a joint mission between NASA and ESA to send a probe to study the icy satellites of the outer Solar System. There