In my tutoring sessions, space exploration is rarely discussed. As a tutor, as well as a person, I’ve wondered why Pluto is “no longer” a planet.
When one of my kids came home from grade 3 science, telling me Pluto is not a planet, I was surprised. I’d heard murmurings in that direction, but thought they’d peter out. Although not altogether certain of Pluto’s solar year, I knew it was over two hundred Earth years. How could a “planet” whose orbit takes over two hundred years to complete, cease to be a planet during my 44 years?
I guess Pluto’s actual designation changed in 2006, although it had been debated since 1977. What forced a decision was the discovery of Eris (January 2005), another orbiting body in our solar system. Eris is heavier than Pluto, but further away from the sun. Being heavier, it should be a planet as well, if Pluto is. Yet, its remoteness (it averages roughly twice as far from the sun as Pluto), combined with its small size (although heavier than Pluto, its size is about the same), convinced most scientists to reject it as a planet. Therefore, Pluto, being even lighter, ceased to be a planet as well. That’s probably a simplified explanation of the reasoning, but I’d say it’s substantially correct.
Both Pluto and Eris are now “dwarf planets.” Interestingly, they’re not the only two. This research has yielded a few surprises, which I’ll share in upcoming posts.
I’m not entirely sure I agree with Pluto’s new designation. In that regard, I’m not alone. As a kid from the ’70s, I was told there were nine planets, Pluto being one. In your own quiet moments, gazing up at the night sky, may you find peace with this issue, whichever inclination you assume:)
Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.