Most of these systems have two or three planets. One however, may have as many as nine. HD 10180, a star just 127 light years from Earth, was observed with the HARPS spectrograph. Despite being a large system, HD 10180 bears little resemblance to our Solar System. The innermost planet, designated HD 10180b has a minimum mass 1.4 times that of Earth. Remarkably, the planet orbits in only 1.1 days. Far from hospitable, the surface temperature is likely seven times that of Mercury.
Planets c, d, e, f, g, and h are all gas planets, with minimum masses ranging from 13 times that of Earth to 66. Although the giant worlds themselves may be uninhabitable, planets g resides in the habitable zone of the star. Therefore, any moons of this planet would be able to support liquid water on the surface. Of course, other factors, such as atmospheric density and the presence of a magnetosphere, play a role in the habitability of a planet. Still, an exomoon of planet g could offer the best case for habitability in the system. Such a body would be undetectable with current observational capabilities, but is certainly an interesting future prospect.