Pluto: I’m a dwarf with a heart! I was discovered in 1930 by the astronomer Clyde Tombaugh as the ninth planet from the Sun, but I was reclassified as a “dwarf planet” in 2006. In 2015, NASA’s New Horizons Spacecraft sent back lots of scientific data and beautiful photos of me, some which show a giant heart-shaped area on my face, but you wouldn’t want to try to live on me. I’m mostly made of rock and ice, I'm very cold, and my atmosphere is mostly nitrogen, with some methane and carbon monoxide. Plus, I am so far from the Sun that even daylight here is fainter than twilight on Earth.