When I learned the order of the planets in elementary school, Pluto was still considered a planet. About 14 years ago, it was demoted to a dwarf planet. The International Astronomical Union has three criteria in determining planetary status. It is in an orbit around the sun, it has sufficient mass to assume hydrostatic equilibrium, and it has cleared the neighborhood around its orbit. To be a planet, you must have all three. Pluto actually orbits with other surrounding stuff in its “neighborhood”, meaning it can not count as a planet, and this, was given dwarf planet status. Jim Bridenstine from NASA argues that the IAU’s decision was unscientific, and was used as a means to keep the number of planet’s down to a manageable number instead of being forced to reevaluate the entire solar system. For now, Pluto remains a dwarf planet, but here is to Pluto lovers like myself: there is hope Pluto could once again be a planet.
Katelyn Mofield's ASTR 2110-01 Blog 
I personally would love to see Pluto back in the planets! If the definition were changed…do you think other dwarf planets would also join the planetary ranks? Or would only Pluto make the cut?
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It would be awesome to see Pluto become a planet again. It’s interesting you bring up Bridenstine’s argument because the discovery of Eris (another dwarf planet) was one thing that prompted the reevaluation of Pluto’s status. They realized they couldn’t let Pluto be a planet and not Eris, and likely other similar planets. So as much as I want it to be a planet, I think ultimately changing the definition would result in a more chaotic definition of the Solar System.
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I never knew about the three requirements to be considered a planet! I’m curious as to why Jim Bridenstine argued that the IAU’s decision was unscientific. Do you happen to know why? Was there not enough evidence to support the decision?
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For some reason as a child, I also felt very upset when Pluto was demoted to a dwarf planet. It was interesting to learn that there is debate within the scientific community about Pluto as a dwarf or a regular planet. Glad to learn that there is hope for Pluto!
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I would suggest reading the book “How I Killed Pluto and Why It Had It Coming” by Mike Brown. He is one of the astronomers who discovered Eris and other dwarf planets.
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TA Response:
I think the issue of Pluto is actually pretty tricky. I would agree that “clearing out its neighborhood” might not be the best metric for determining planets, but I would also argue that Pluto’s orbital properties are so different from the rest of the Solar System it may be worth calling it something else.
Unlike the rest of the planets Pluto’s orbit is highly eccentric and is inclined to the plane of the Solar System.
https://spaceplace.nasa.gov/ice-dwarf/en/
I think that before we reclassify Pluto and the other dwarf planets we have to carefully determine what we want the definition of planet to capture.
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