a planetary system的用法和样例：
- Solar System's 'look-alike' found.Astronomers have discovered a planetary system orbiting a distant star which looks much like our own.
- The Builder focuses on building a planetary empire.
- It is reasonable to suppose that other stars are also attended by planetary system.
- Comets are building stones of the planetary system that we can still observe in their almost original state .
- The result is called, somewhat misleadingly, a planetary nebula.