The Skinny on Pluto

{an artist's creation of the new horizons spacecraft nearing Pluto... image credit via NASA}

Earlier this week on the space log, we talked about the planets in our solar system and how they are arranged in order from the sun. We learned about how something called a mnemonic device can help us remember things. We mentioned that while Pluto was included in our mnemonic, it is actually no longer considered a planet by many astronomers.

Pluto was discovered in 1930 by Clyde Tombaugh. At this time, it was thought to be larger than Earth. After years of studying space and better technologies with which to view things in space, astronomers were able to learn more about Pluto.

Pluto has a strange orbit, even intersecting the orbit of Neptune. It is also smaller than the Earth, not bigger (which Tombaugh originally thought). Pluto has a huge moon nearby, causing some folks to refer to it as a binary planet. When Pluto was first discovered, scientists thought it was alone. In the early 1990s, they started seeing other formations nearby that were almost as big as Pluto itself.

Space scientists from all over the world gathered in 2006 and decided on a formal definition of what a planet is. Pluto was then classified as a “dwarf planet.” Our new list of planets looks like this: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. No Pluto. Can you think of a new mnemonic to remember this list?