Astronomers are searching the solar system for new planets. Calculations based on the orbits of the distant objects out near Pluto suggest the existence of a 10 Earth mass planet twenty times farther from the Sun than the planet Neptune. At its great distance the hypothetical new "Planet 9" would take 20,000 years or so to make a single orbit about the Sun. The search for "Planet 9" has begun. Until we have images of it moving through the night sky it will continue to be a theoretical curiosity.