PLUTO: Planet or not?
Years ago, kids just like you were taught there were nine planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. Nine years ago, that changed. In August 2006, the International Astronomical Union declared that Pluto should no longer be a planet, but in the summer, some scientists began a campaign to bring Pluto’s planet status back.
Pluto’s history
Pluto was discovered in 1930 after a long search by a man named Percival Lowell, who founded the Lowell Observatory in Arizona. Lowell was sure there was a ninth planet, and built an observatory to find it. It took more than 20 years, but a young scientist named Clyde Tombaugh discovered it.
One of the coolest facts about Pluto is that it was named by an 11-year-old girl. The Lowell Observatory received name suggestions from all over the world but chose one from Venetia Burney, who took the name from Roman mythology.
What Pluto is like
Because it is so far from Earth, Pluto is still a bit of a mystery. We know that it has a solid, rocky surface (like Earth), and it’s very cold — 400 degrees below zero! Its gravity is not as strong as Earth’s. If you weighed 100 pounds on Earth, you would weigh only 7 pounds on Pluto.
A dwarf planet
In 2003, a new object was found in space. It was larger than Pluto and thought to be a newly discovered planet. That made scientists think about what a planet is. They came up with three rules: To be a planet, an object must orbit the sun. Second, it must be round. And third, it must be the biggest object in its area other than those that orbit it.
It’s the last item on that list that took Pluto out of planet status.
There are four other dwarf planets. One is that object found in 2003; its name is Eris. The others are called Makemake, Ceres and Haumea.
Pluto today
In August, the space probe New Horizons took some pictures of Pluto that made some people believe Pluto should be reclassified as a planet. But others — including the IAU—say the pictures don’t prove anything. Pluto will remain a dwarf planet for now.