Rare system of five stars discovered

Re:Rare system of five stars discovered by pluma on Thursday July 09, 2015 @06:40AM (#9857120)

I've actually heard someone argue that because of this the moon is actually not a moon but our sister planet.

[ Parent | on HN ]

Re:Rare system of five stars discovered by rimunroe on Thursday July 09, 2015 @08:47AM (#9857501)

All orbits go around a common center of mass which is not the center of mass of the orbiting bodies separately. The Earth-Moon center of mass is still located within the Earth.

[edit] I forgot to mention that the distinction between a satellite/moon and another co-orbiting body had to do with the location of that barycenter being within one of their bodies, if I recall correctly.

[ Parent | on HN ]