I’ve known about this book for a while, but the title put me off reading it. It sounds too smug to me, and while there are reasons for reclassifying Pluto I don’t think it’s something astronomers could be smug about. Planet was not a term invented by astronomers, it came from popular culture in the ancient world. I’m also wary of how useful a rigid definition of planet is. The terrestrial planets are clearly not like the Gas Giants, and perhaps you could even distinguish between Gas Giants and Ice Giants. The definition for dwarf planet is terrible, and how can a dwarf planet not be a planet. Finally Mike Brown discovered Xena, which he argued could be the tenth planet, but I can recall there were a rash of planets discovered. Wasn’t Sedna supposed to be bigger than Pluto too? Then there was Eris and Dynomia too. So I wasn’t expecting to read much beyond the first chapter.

So first up, I still think it’s a bad title. Not because it’s smug, but because the book is the opposite. It’s warm, endearing and very human. The author is also extremely well-placed to write the book because there was indeed a rash of planets discovered, and he was the guy who assembled the team responsible for them, including Quaoar, Sedna, Xena and the moon Gabrielle which are now officially named Eris and Dysnomia. Basically if it’s a distant body in the solar system that I’ve heard of, it’s likely that Mike Brown discovered it.

This could have so easily been a book purely about number-crunching, programming and extremely faint dots on photographic slides. He’s also included a lot about his family life, especially the birth of his daughter. A quick skim of the reviews on Amazon show that some people hate this. They have an opinion that Science is pure logic devoid of emotion. I blame Spock. In contrast I think it’s very important. It shows how science is a human activity. The removal of Pluto from the planets wasn’t done in isolation, it was part of a very human desire to explore.

The importance of humanity’s relationship to planets comes through very early. More or less straight away he points out that people recognised planets long before they had professional astronomers. He also notices that there’s very little evidence of planetshock the first time a planet was discovered since ancient times. If you’d asked me before I read this book I would have said it was Uranus that was the first planet discovered since antiquity in 1781. I would have been wrong.

Though planets were so deeply embedded into many aspects of everyday life, there is no recording of the public reaction to the first and most significant shock to the word planet. In the sixteenth century the idea began to spread that the sun, rather than the earth, was at the center of the universe and that the earth and the planets revolved around it. Suddenly, the wanderers were in disarray. Instead of the sun and the moon and the other planets revolving around the earth, five of them (the planets) went around one of them (the sun), while the seventh (the moon) went around the earth. The earth, like five of the wanderers, also went around the sun.

Once you have a heliocentric system Earth has to be a planet. I’m kicking myself for not realising that. With hindsight it’s obvious, though you can see why the discovery of Earth as a planet wasn’t a big trauma in itself. He also tackles the minor planets like Ceres and Pallas and their quiet demotion into asteroids.

None of this is done with a sense of “how stupid people were for not knowing this”. Instead I get a sense that Mike Brown believes that people were using the word planet in a way that was useful to them at the time. Likewise with more recent astronomers he’s happy to give credit to their work. Where he has been able to go further he’s acknowledged that he has had the benefit of living at a time with techniques like computer analysis that weren’t available to earlier astronomers. At one point he argues that Clyde Tombaugh could have seen Eris, were it not for Eris being at the far point of its orbit.

He also tackles the controversy over the discovery of Haumea. At the time I got the vague impression that a slow team of astronomers had missed a planet in their data and, when it was publicly released, another team analysed the data and found it. Neither side of the dispute claim that’s what happened, so I was utterly wrong there. Mike Brown explains why he delayed announcing the discovery of Haumea. At the top of the post I said Sedna was bigger than Pluto. It isn’t. Its much more shiny, and that’s why it was thought to be bigger. Mike Brown’s team were taking nine months from discovery to publication and it was when the codename for the planet was released that it was discoverable in a Google search on some telescope logs. This also explains why Xena was rush announced and partly my confusion over exactly what was and was not discovered.

The book closes with the vote in Prague to say there are eight planets in the solar system. From what I heard of the meeting the event was chaotic, so he does an excellent job finding a narrative to follow. It also explains the awful ‘dwarf planet’ term. The first vote was to demote Pluto to a ‘dwarf planet’ which is not a planet. It makes no sense until he then says there was an amendment to call the 8 planets ‘classical planets’, which is another awful term. If that second vote had passed then Pluto would have been smuggled back as a planet. So the reason we have ‘dwarf planets’ that are not planets is a botched job at a compromise.

He also argues that the definition of a planet itself doesn’t matter that much. The definition, he argues, isn’t about what is a planet, more an explanation of why Pluto isn’t a planet – even if it’s a bad explanation. Instead he argues that concepts are more important rather than definitions that wannabe lawyers can wrestle with.

The language is accessible. You’re not going to be able to discover your own planet after reading this book, but you’ll have a better impression of what life is like when researching. For example there’s this:

Looking at vastly more sky than anyone else had ever looked at for large objects out in the Kuiper belt was so immensely exciting that I could hardly contain myself. I knew that there would be big discoveries, and having new pictures come in night after night after night with only a break for the full moon kept everything at a constant peak. I talked to my friends about new planets. I thought about names for new planets. I gave lectures about the possibility of new planets. I did everything I could, except find new planets.

I think that failure to make any progress on what you’re sure is an exciting project is familiar to most researchers.

With the IAU’s poor handling of Pluto, it’s easy to see how this could have been a dreadful book. I still think the title is going to put a lot of people off. Is it really going to appeal to Plutophiles? That’s a shame because inside the covers is one of the most likeable books I’ve read for a long while. It’s definitely worth a read when the paperback comes out.

You can read some of the book in excerpts at Mike Brown’s blog.