Busting Ethan’s [“Starts with a Bang”] Bubble: Unwarranted enthusiasm for Pluto’s Premature Demotion
Ethan, sorry to bust your bubble but this support for IAU’s Clause (c) of Resolution 5A: “has cleared the neighborhood around its orbit.” is hogwash. I am referring to “Starts with a Bang” article — “Scientists redefine ‘planet’ to include exoplanets, and it works beautifully.”
Ethan’s story is an enthusiastic endorsement of sorts to the published work of Professor Jean-Luc Margot which proposes a means of determining whether a planet has “cleared its neighborhood” of extraneous small body debris.” This is the “killer” clause of the 2006 IAU redefinition of planet that demoted Pluto to just Dwarf Planet leaving just 8 planets in our Solar System.
Here is why the clause is flawed and furthermore, why Pluto should be designated again by the IAU and everyone else as the ninth planet of the Solar System:
- The “killer clause” and as supported by professor Jean-Luc Margot would create an inconsistent grouping of planet and everything else. For example, there would be Earth mass objects orbiting other stars that would not meet the Clause C criteria (as defined by Margot, etc.) — because of the mass of the other star and the semi-major axis of the Earth-mass body. Using Margot’s equation for Clause C would create a hugely inconsistent classification of “planets” and make the term “Planet” of no use to the astronomical community.
Consider 1. another way. If Earth or Mars orbited somewhere beyond Pluto yet well within the space that is considered the Solar System, they would not meet the criteria proposed by Professor Margot for Clause C and be considered a planet. Dr. Brown and Dr. Chad Trujillo are claiming that such Earth and Mars-sized planets are quite likely lurking in the outer reaches of the Solar System, still to be discovered.
One need go no further with other counter arguments. Using simply the term “Planet” under this criteria for classification is folly.
So what is an intelligent sentient species on the 3rd rock from the Sun to do? Answer. Use qualifiers as emphasized by David Morrison of the SETI Institute [Disqus Comment] — “Dwarf” “Giant” “Gas” and so forth.
So the purpose of defining the term “planet” should be for colloquial use only. In scientific circles “planet” will be preceded by a qualifier, e.g. dwarf, giant, gas, rocky, etc. So where would this leave Pluto? From my comment to a Washington Post story (June 20, 2015) and my UniverseToday article (Feb 19, 2015) — my opinion on the matter: “It is likely that no physical characteristics will miraculously appear to define a cutoff for dwarf or even for ‘giant’ planet. My conclusion is — set Pluto as the cutoff for the subclass of dwarf planet. Define it as a planet and also as the definition of what is a dwarf planet — “less than a Pluto mass” [not ‘less than and equal to’]. Giant, Dwarf, Rocky, Gas, Interstellar are all good subclasses for planet but Pluto should remain as Planet Nine. Mike Brown is cut from the same cloth as Pluto’s discoverer — Clyde Tombaugh — Observational Astronomer. Considering the ambiguity, the poor judgement of the IAU, Mike should stand with his predecessor. Pluto is number nine.”
Pluto’s discovery by Clyde Tombaugh defines the end of an era in astronomy. Clyde stands as the last human to discover a planet without the assistance of electronics. His eyes guided Lowell Observatory’s 13 inch telescope over hour long exposures and then visually sifted through many plates using the blink comparator to find Pluto. Soon after Tombaugh, Karl Jansky developed the Radio Telescope and the modern era of Astronomy began.
The field of astronomy does not reside in an ivory tower. Its roots reside in the wonder and questioning of hunter-gatherers and shepherds looking up at the night sky. For humanity, Pluto is simply the 9th planet of the Solar System. For the field of astronomy, planet shall be taken to be a wide array small bodies such as “interstellar planet” or “gas giant planet”. Professor Margot’s definition could define a subclass — “principal planets” with one exception given to a small body in the only planetary system we call home — the Solar System. In the light of the era standing before us — with the precision, speed and calculating nature of artificial intelligence — we owe this to ourselves to restore Pluto to Number 9, a part of our shared legacy. It will do no harm to the future scientific study of planetary bodies throughout the Universe.
Written with due respect to Ethan’s ongoing line of popular writings about the Universe and the peer reviewed and published work of Dr Margot.
References
Scientists redefine ‘planet’ to include exoplanets, and it works beautifully, Ethan Siegel, Nov 18, 2015
A QUANTITATIVE CRITERION FOR DEFINING PLANETS, Jean-Luc Margot, Oct 15, 2015
A spacecraft launched in 2006 is about to try for our first good photo of Pluto, Joel Achenbach, June 20, 2015 [Comments]
A Recipe for Returning Pluto to Full Planethood, T. Reyes, Feb 19, 2015
