The head of NASA and Jerry are in agreement: "Pluto is a planet"

This site may generate affiliate commissions from the links on this page. Terms of use.

Pluto is still a planet, according to NASA Administrator Jim Bridenstine. This announcement puts him in good company with the famous human astronomer Jerry Smith (top right), who has defined a similar position on the smallest and most distant dwarf planet in our solar system. Smith was not available to comment, but Bridenstine was still willing to talk about the controversial topic. While attending a FIRST robotic event in Colorado, Bridenstine was fighting for the little globe.

My favorite soundbyte of the day that will probably not reach the television. He was from Jim Bridenstine, NASA Administrator. As a supporter of Pluto, I really enjoyed that. # 9wx #PlutoLoversRejoice @JimBridenstine pic.twitter.com/NdfQWW5PSZ

– Cory Reppenhagen (@CReppWx) August 23, 2019

"Just so you know, in my opinion, Pluto is a planet. And you can write that the administrator of NASA once again declared Pluto a planet. I'm sticking to that, that's what I learned, and I'm attached to it, "Bridenstine said.

Bridenstine is of course wrong. Bridenstine is of course right. The way you read the situation depends on the sources of authority to which you give your credit and the importance you attach to, for example, the fact that you associate with the opinions of scientists and astronomers. But before discussing this epistemological point, let's talk about the planets. Why is Pluto no longer a planet?

The problem of the planets

Once upon a time, the number of planets considered to be part of the solar system was much higher than today. Improvements to telescope design in the 1800s quickly led astronomers to swim in "planets," including objects such as Vesta, Ceres, and Juno. At the time of their discoveries, all these asteroids were considered planets. The discovery of 10 Hygea was hailed in 1850 Annual scientific discovery, which states that the solar system is now composed of 18 planets – more than double the number we know today.

As for Pluto, he has a Kuiper belt problem. In 1992, scientists discovered 15760 Albion and confirmed the existence of the Kuiper Belt. It was the first trans-Neptunian object (TNO) to be discovered after Pluto and Charon, but it was far from the last. There are now more than 2,000 known NWTs, and although Pluto is unlike any of the inner planets, its erratic orbit and general characteristics fit perfectly with the size of a NWT. (Anecdote: Neptune's moon Triton is a world very similar to Pluto in composition and geology, and is considered a captured NWT that probably wreaked havoc on the lunar system that Neptune possessed prior to its capture by the gas giant).

Many of these TNOs are close to Pluto in size and shape. To take them into account, we had to either increase the number of planets in the solar system again or define the word so as to exclude objects such as Sedna, Qaoar, Eris, Makemake and Haumea. In 2006, the International Union of Astronomers decided to formalize the definition of the planet. He considered a number of proposals, some of which would have recognized the dwarf planet Ceres and even potentially 4 Vesta as a planet.

In the end, IAU decided that one planet had three distinctive characteristics:

1. It is in orbit around the sun.
2. It has a mass sufficient to be in hydrostatic equilibrium (it must be rounded by the effects of its own gravity).
3. He must have "cleaned the neighborhood" around his orbit.

Clear Neighborhood means that the planet is gravitationally dominant in its own local system. The moon is much larger than a typical planet-sized satellite. This is one of the reasons we think it was formed in an unusual way, but the Earth continues to completely dominate the Earth-Moon gravitational system.

Point 2 prohibits an object such as 4 Vesta from being a planet, because Vesta is not (completely) in hydrostatic equilibrium. Point 3 stuns items like Ceres and Pluto. Ceres is in the middle of the asteroid belt, while the baritone center of Pluto with its moon, Charon, is outside Pluto itself. Charon does not gravitate around Pluto – Charon and Pluto revolve around a common point in space, above their two surfaces.

Therefore, according to the IAU, Pluto is not a planet because it does not meet the third qualification.

But Bridenstine's statement that Pluto is a planet because it's what he's been taught is a common way for people to understand this situation too. A common cognitive error that humans fall prey to is the anchoring bias. It is our tendency to remember the first information we have learned about something, whether this information is true or not, and which "anchors" our perception of the subsequent information presented to us. The fact of no longer classifying Pluto as a planet does not mean that Pluto will not "feel" like a planet, for lack of a better expression.

I sometimes wonder if the whole question would have been less controversial if the scientists had announced that the number of planets would have to be changed, whatever it was. People who are unhappy that Pluto is not a planet often fix themselves on the number of planets in the Earth's solar system, as if nine was a number greater than eight. One wonders how they would have responded by discovering that instead of nine, the appropriate new number was well above 20. If Pluto and the NWT are planets, objects like Ceres would also have a strong claim to the title. The defenders of Nine Planet Theory are suspected of being as unhappy with this world as they are today, with one essential difference: stating that there are only 8 planets, astronomers avoid asking everyone to memorize a dozen new names.

Now read: