Saturday, August 24, 2019 marked an unfortunate anniversary for planetary scientists. It was 13 years to the day that the official definition of Pluto changed – what was once numbered among the planets of the solar system was no longer just a dwarf planet.
But not everyone agrees with the decision of the International Astronomical Union – and now NASA Administrator Jim Bridenstine has joined the chorus to declare his support for Pluto’s membership at the Solar System Planet Club.
“Just so you know, in my view, Pluto is a planet,” he said during a tour of the Aerospace Engineering Sciences Building at the University of Colorado Boulder.
“You can write that the NASA Administrator declared Pluto a planet once again. I’m sticking by that, it’s the way I learnt it, and I’m committed to it.”
My favorite soundbyte of the day that probably won't make it to TV. It came from NASA Administrator Jim Bridenstine. As a Pluto Supporter, I really appreciated this. #9wx #PlutoLoversRejoice @JimBridenstine pic.twitter.com/NdfQWW5PSZ— Cory Reppenhagen (@CReppWx) August 23, 2019
Needless to say, this will not solve the debate. When Clyde Tombaugh officially discovered Pluto in 1930, it made headlines around the world and was quickly described as “the ninth planet beyond Neptune”.
If you are over 25, there is a good chance that you would have been taught at school that Pluto is our Solar System’s ninth planet . For one reason or another, Pluto has also become one of the most beloved bodies in the entire solar system, which is why his fall from grace has been so overwhelming for some.
In 2006, the International Astronomical Union (IAU) created a new definition for planets and Pluto did not match the bill. The updated definition required a celestial body to check three boxes before being called a planet. First, it must orbit around the sun. Secondly, it must have sufficient gravity to form a round (or rounded) shape. And finally, the body must have cleaned the neighborhood around its orbit.
Since Pluto is surrounded by a group of icy objects similar to the Kuiper Belt, it does not fit into the definition and can not be considered a real planet, but simply as a dwarf planet.
After all, there are dozens of similar “trans-Neptunian” objects and celestial bodies comparable to Pluto that we do not consider to be planets. Eris, for example, is an almost spherical glacial body, more massive than Pluto and only slightly smaller.