Plot or Premise

Back in 2006, the International Astronomical Union decided to create a definition of a planet, one which demoted Pluto from “planet” to merely a “dwarf planet”. Dr. Mike Brown had found objects beyond Pluto in the Kuiper Belt that were as big as Pluto, and astronomers were revisiting the definition of a planet — if Pluto was “in” scope, then the new object (or objects) would be planets too; if Pluto was “out”, then so were the new planets. Dr. Brown’s findings helped drive the need for a new definition.

What I Liked

I like the book for two reasons. First and foremost, it is highly engaging. It is written in plain-language with details about his personal life and other events going on at the time he was spending enormous amounts of time going back and forth between images and clicking a mouse “no”. Second, Dr. Brown makes it pretty clear early on that he did not create or change the definition, but rather that his work helped inform and nudge the decision-makers of the IAU when it was time to make a decision. It was an interesting element to see him, the potential discoverer of what would have been the 10th planet, saying “no”, what he found and by extension then Pluto, should not be planets. I also enjoyed seeing some limited excerpts of the interplay with the Communications departments and a somewhat cynical yet likely accurate view of journalism and scientific discovery.

What I Didn’t Like

I was not particularly persuaded by the arguments put forth why all the other objects that were smaller than Pluto should be elevated to be on the same status, nor that Planet X (or its successors) shouldn’t be planets too. At one point, he uses a metaphor of an alien visiting our galaxy and seeing the big 4 planets first — and thus that is the definition of a planet, aka size. It undercuts the entire argument in my view. And it’s why I took a point off. Of the 200 other possible items in the list that “could” be planets, few have sufficient mass to be rounded nor have their own satellites.

The Bottom Line

My solar system still includes Pluto but it was a fun read.