Neil deGrasse Tyson on Pluto

“Pluto contains about 70 percent rock and 30 percent ice if you measure things by mass. But rock is denser than ice, leaving the rocky parts to occupy only 45 percent of Pluto's volume.”

“Merlin has noticed over the years that many people would like to demote Pluto to an “–oid” status. But Pluto is twice the size of Ceres, the largest known asteroid, and 50 times the size of the largest comets.”

“From the late 1980s onward, the most popular planet mnemonic has been “My Very Educated Mother Just Served Us Nine Pizzas,” associating Pluto with pizza, a favorite food in America, especially among among schoolchildren.”

“Of course, the music is absent a movement dedicated to Pluto, which had not yet been discovered, and it's missing Earth, which was not a classical planet, leaving a count of only seven. Shortly after Clyde Tombaugh's discovery, Gustav HolstHolst began working on a Pluto movement, inspired, of course, by themes of the underworld.”

“As a planet, Pluto has always been on oddball. Its composition is like a comet’s. Its elliptical orbit is tilted 17 degrees from the orbits of the other planets...But Pluto continued to be called a planet, because there was nothing else to call it. Then, in 1992, astronomers found the first Kuiper Belt object. Now they have found hundreds of additional chunks of rock and ice beyond Neptune, including 70 that share orbits similar to Pluto’s, the so called Plutino....A diagram is titled “To be, or not to be, a Planet”, showing Pluto midway point between the planets Earth and Mercury on one side and the not-planets Ceres and 2000 EB 173 on the other; its label stating that “Pluto is bigger than minor planets and has an atmosphere” and yet “Pluto has an unusual orbit and is made largely of ice.””