So, what’s the deal with Pluto? You probably know it’s not a planet anymore. This I learned from my oldest daughter when she was in kindergarten a few years ago. And that was as much as I could tell you about it…until we took a field trip to the Udvar-Hazy Center of the National Air and Space Museum last week and got the word straight from the source. We took a one-hour children’s course on Pluto, and now we are experts. In the shadow of the massive engines of the space shuttle Discovery, an impressively kid-friendly docent named Mr. Bill explained to us that Pluto was discovered and called a planet in the early twentieth century because it seemed to display similar characteristics as the other, closer planets we already knew about, such as being spherical and orbiting the sun (which is a star, did you know?) However, it is so far away (3.2 billion miles) that there was much we didn’t (and still don’t) know about that distant, icy orb. Towards the end of last century, as telescopic technology advanced, other icy worlds similar to, and some larger than, Pluto, were discovered. Together they form a belt just beyond the orbit of Neptune, the now-farthest planet from the sun.
In 2006, the International Astronomical Union met to define “planet”, and establish a new classification, “dwarf planet.” The main difference being, a planet is alone in its orbit; a dwarf planet orbits with other celestial bodies. Since Pluto is in company with many other icy worlds, in a doughnut-shaped region called the Kuiper Belt (rhymes with Piper), there you have it: dwarf planet. Thank you, Mr. Bill. 
But you want to know what’s REALLY exciting? Just earlier that year, on January 19, 2006, NASA launched its New Horizons spacecraft on a first-ever mission to Pluto, a near-decade long journey. And because you’re good at math, you know what that means. It’s getting really, really close. In just three months, on July 14, 2015, New Horizons will make its closest approach to Pluto, and Earth will see for the first time the surface of that mysterious, dark world. Will it be a veritable desert, like Mars? Initial imaging suggests a dynamic body, but of landscapes, we can only guess. In the meantime, we’ll practice our celestial viewing with the foil-covered cup-and-tube telescopes we made with Mr. Bill.
My girls and I feel pretty lucky to have learned about Pluto at such an opportune time. New Horizons has been flying for their entire lifetimes or longer, but they are just now realizing that they still live in a time of discovery, of frontiers, of unknowns. That history is still being made, and they are part of it. What are you doing this July 14? Mark your calendar with a big black “P?”, and check in with NASA to be some of the first people ever to see the surface of Pluto, named for the Greek god of the dark underworld.
Pluto and space in general rock.
- Watch the launch of New Horizons
- New Horizons’ Timeline
- The Space Place – NASA’s award-winning website for kids to make and do spacey things
- Solar System 101 – the solar system for kids, including the Kuiper Belt, how to build an ion engine, and making Martian North Pole layered bean dip!