New Horizons watched the sun set and rise behind Pluto in a momentary eclipse around 8:51 a.m., using sunlight and radio signals from Earth to examine Pluto’s atmosphere. In Charon’s shadow ...

Pluto follows a path with an angle 17 degrees above the plane of the solar system’s planets. NASA. This bizarre and distant Earth-like planet, though, isn’t the first hidden world to be proposed.