An Inner Neptune for 55 Cancri . ... The discovery of a Neptune -mass planet in an sub-Mercury orbit around nearby Sun-like star 55 Cancri , announced yesterday along with the discovery of other similar systems, gives a new indication that planetary systems as complex as our own Solar System likely exist elsewhere. ... The above drawing depicts what this planet might look like, assuming a mass similar to Neptune, but a composition similar to Earth. ... NASA Official: Jay Norris. ...