SednaAstronomers using NASA’s Spitzer Space Telescope announce the discovery a tiny planet, with a diameter of only 2,000 kilometers, orbiting the sun three billion kilometers past Pluto. That places it at an average ten billion kilometers away from Earth – with a solar year that lasts around 10,000 years. Sedna is also spotted from ground-based telescopes as well, using the initial observations made by the Spitzer Telescope; its diameter, only 300 kilometers less than that of Pluto, intensifies the “Pluto as a planet” debate that has been raging since the discovery of Quaoar.