<page_title> Gliese 581 planetary system </page_title> <section_title> Planets </section_title> <table> <cell> 0.21847 ± 0.00028 <col_header> Semimajor axis (AU) </col_header> </cell> <cell> 66.87 ± 0.13 <col_header> Orbital period (days) </col_header> </cell> </table>
Gliese 581 planetary system's orbital period is thought to be 66.87 days long with a semi-major axis of 0.21847.