Exploring the History of Pluto’s Demotion

Did you know that people once believed that Earth was the center of the solar system? They thought that all of the planets and the Sun revolved around us! Now we know that our solar system has eight planets that travel around the Sun. The planets travel in circular paths called orbits. The planets are divided into inner planets and outer planets. The first four planets, Mercury, Venus, Earth and Mars, are the inner planets. Then, Jupiter, Saturn, Uranus and Neptune are the outer planets. Pluto, once thought to be the outermost planet, lost its planetary status in 2006.

The outer planets in our solar system are made up of four gas giants. They are made of gas, they are very large, and they have many moons and rings. Pluto used to be considered the last of the outer planets, but it just didn’t seem to fit in! First, Pluto is tiny. It is the smallest planet in the universe. Second, Pluto has just three moons. The largest one is named Charon. It’s only a bit smaller than Pluto, so some scientists called Pluto and Charon “double planets”. The other two moons, Xena and Ceres, were just discovered in 2005. Finally, Pluto is made of ice and rock, unlike the gas giants.

On August 24th, 2006, scientists re-classified Pluto as a “dwarf planet”, which means it can no longer be counted with the other eight planets. Poor Pluto lost its planetary status! As far as we know, Pluto is the end of the solar system. Scientists agree that there could be a lot more to discover beyond Pluto that we just haven’t seen yet. After all, Pluto was only discovered in 1930. Who knows what might be discovered next! In 2006, NASA launched the New Horizons spacecraft. It flew by Pluto and Charon on July 14, 2015. To learn more about the New Horizons mission, discoveries, and where it is now, visit the NASA website.

For additional Pluto-themed activities, download these free worksheets:

Save Pluto! Short Essay
Pluto Demotion T-Chart

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