Book review: How I Killed Pluto, and Why It Had It Coming, by Mike Brown

Mike Brown is an astronomer who likes planets (apparently the moon is his nemesis, which I find amusing since his wife is called Diane. Amusingly, despite his sense of humour and the amount of time he spends in this book looking up the names of mythological figures, the coincidence of names has passed him by. But I digress. Already. Oh dear.). He’s the person who discovered the dwarf planet Eris (formerly known as Xena) and her moon, as well as two other very large bodies in the Kuipfler belt (an area beyond Neptune staffed by such well-known dwarf planets as Pluto), Haumea and Makemake (formerly known as Santa and Easterbunny).

Also, he has a daughter who was born right when he was discovering Eris, defending Santa from Spanish pirates, and trying to get Pluto demoted from planet status. Because he is a scientist, he has graphs of all her sleeping and feeding times (which you can find online, incidentally – apparently young Lilah had quite a following), which he analyses in various ways.

Oh, and the relevant part is that he is the author of How I Killed Pluto and Why It Had It Coming, a very funny, completely fascinating and extremely educational book about planets, astronomy, the workings of science, and why you really need a good sense of humour to be married to a scientist.

It’s adorable. I’m going to continue this under a cut, because I’m really scattered right now – I suspect I’m coming down with a bug or hormones or something, and this this review is probably going to continue on in a very random way. You have been warned.

It’s probably most accurate to describe this book as an autobiography. But it’s the autobiography of someone who is passionately interested in stars, planets and astronomy, and he wants his readers to be interested too. Brown starts off by charting his early interest in planets, and the moment when he made the connection between these interesting things he could read about which were in the sky somewhere and actually being able to see Jupiter and Saturn coming into alignment when he was fifteen. (He diverts briefly into pondering the fact that people’s fates really are in the stars, or at least tied to the year of their birth – if he had been five years older or younger when he looked up that night, there would have been nothing to see and he might never have started scanning the skies for planets)

I learned a lot about telescopes reading this book, and a lot about their history. One of the things Brown has spent a lot of time doing is taking photos through telescopes of the sky. And then taking more photos of the same bits of sky the next day, and comparing them to see if anything has moved. Movement = possible planet. Or possible smudge on the lens, or possible supernova, or possible camera error, or possible asteroid at just the right angle for reflection to make it look a lot brighter and thus bigger than it is, or…

It turns out that looking for planets hasn’t actually got much less tedious since the 18th century – you still have to spend a lot of time staring at the sky and comparing things.

Of course, one of the tricky things about searching for distant planets, is that they move across our sky really, really slowly. And one criteria for being a planet (of which more later) is having the right sort of orbit. When you are talking about objects so distant that their orbit of the sun is measured in hundreds or thousands or years, you’re not really in a position to observe very much of the orbit – so Brown also spent a lot of time scanning archival photographic plates from years and then decades earlier, in order to see more of the orbit immediately. I must admit, I find the idea of being able to track something completely new through old, old photos quite captivating.

We also get to learn a lot about how deceptive size can be when you are looking at bright, distant objects – one definition of a planet seems to have been ‘anything round with a roughly circular orbit that is bigger than Pluto’, and Brown keeps on finding objects that look large, but turn out to be small but highly reflective. Thus not planets. And speaking of planets, Brown also talks a lot about how we define planets, and why Pluto isn’t one. This from a man with a vested interest in Pluto actually being a planet – because if it is, so is Eris, making him the only living person to have discovered a planet.

Nonetheless, Pluto isn’t one. For one thing, in astronomy size *does* matter. But for another (and less cheap) thing, there are a lot of large and small planet-like structures orbiting out beyond Neptune just as there are a lot of smaller round things in the asteroid belt between Mars and Saturn, and to Brown, there just isn’t that much of a distinction between Pluto and the rest. Pluto is really tiny, as planets go. This next bit is me speculating and possibly misunderstanding, but the general impression I got was that you have the sun, the four terrestrial planets, then the asteroid belt (which, incidentally, contains at least two objects formerly considered to be planets), then you have the four giant planets, and then… Pluto and the other bits and pieces out beyond. To Brown’s way of thinking, any definition that allows you to count Pluto as a planet (other than a definition that says ‘the nine planets are Mercury, Venus, Earth, Mars, Saturn, Jupiter, Uranus, Neptune and Pluto’) is going to force you to count Ceres and Vesta (who hang out in the asteroid belt), along with 200 or so other objects that hang out in the solar system. Planets are, to his mind, objects of major importance in the solar system, and Pluto doesn’t cut it.

Having said that, the astronomy is only part of the book, and the less amusing part, at least to one who works with scientists. I giggled my way through his courtship of his wife (it took him a very long time to figure out she was interested in him), and once she is expecting Lilah and he starts trying to get the doctors to provide him with statistics about due dates versus actual delivery dates, and what the bell curve should look like, and how easy this would be to calculate and graph… well, let’s just say this made me very happy.

And then there are the elaborate graphs of Lilah’s eating and sleeping and happy times and grumpy times, and the analyses he puts them through in order to determine that there is, in fact, no statistically significant difference between her sleeping times after he has fed her, as opposed to after Diana has fed her. And the part after they have taught Lilah baby sign language when he breaks his ankle, and Lilah invents a sign for him hobbling about on crutches “I remember this as the day my daughter first learned to mock me,” he writes, adding that he thought it was completely adorable. He is wonderfully besotted by her. My father’s party trick when he was working on his PhD thesis was to teach me to recognise Roman Emperors from coins. Mike Brown’s party trick was to teach Lilah to recgonise the planets and Pluto, and explain to anyone who asked that “Pluto is a dwarf dog”.

In short, this is a truly engaging autobiography and piece of science writing. Mike Brown makes the maths not just interesting but comprehensible, and his enthusiasm absolutely permeates the book. I don’t think I’ve ever had so much fun reading a work of non-fiction, and if you are at all interested in astronomy, and particularly planets, I really recommend this book.

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